Root length density

Hemp (Cannabis sativa L.) is mainly grown for its fibre and is considered a desirable crop for sustainable production systems. In a field trial carried out over two years in Northern Italy the root system of a hemp crop, cultivated at contrasting plant densities, was sampled and analysed with an image analysis software. Root length density (RLD) was highest in the first 10 cm of soil, almost 5 cm cm −3 ; it decreased progressively until the depth of 130 cm, a part from a peak at 90-100 cm in response to a perched water table. Roots were found to 130 cm of depth in one year and to 200 cm in the other. Root diameter was finer (190 μm) in the upper soil layer, it increased with depth until 100 cm, and remained constant at 300 μm thereafter. Following the same trend of RLD, root biomass was highest in the first soil layer; 50% of the root biomass was found in the first 20 cm or 50 cm when taproot biomass was considered or not. Total root biomass was 3.21 t ha −1 and 2.41 t ha −1 in the two years of trial, but the ratio between aboveground and below ground biomass was constant at 5.46. None of the root parameters were significantly affected by plant population, which seems to confirm the plastic behaviour that hemp shows for aboveground development. The high root biomass production measured in this study, especially in deeper soil layers, provides additional evidence of the positive role that hemp can play in sustainable cropping systems.

Besides aboveground interactions, pruning of trees may also modify their rooting pattern for which a better understanding is needed for the optimisation of agroforestry systems. Thus, variation in fine root (d ≤ 2 mm) distribution of pruned trees and crops were assessed during three cropping seasons by sampling soil layers at 10 cm intervals up to 50 cm and at four distances from tree trunk. Three crown pruning treatments (totally-pruning, half-pruning and no-pruning) were applied to karité (Vitellaria paradoxa) and néré (Parkia biglobosa). In 1999, 59% (0.477 cm cm −3) and 69% (0.447 cm cm −3) of fine roots for karité and néré respectively occurred in the upper 20 cm with a significant decrease in root length density with soil depth. However, in 2000, totally-pruned trees of néré and karité showed 32% (0.051 cm cm −3) and 34% (0.078 cm cm −3) of their density in the upper 20 cm whereas root distribution in 2001 was similar to that of 1999. Thus, pruning to reduce belowground competition for the benefit of associated crops can be recommended in the light of the temporary reduction of root density in crop rooting zone and consequently the increase in crop production.

Recent studies in salt marshes have demonstrated the role of plant roots in sediment stabilisation, and hence the importance of marshes in providing coastal protection. However, the relative role of root traits and environmental factors in controlling sediment stability, and how intraspecific variability of root traits vary within and among marshes, remain poorly understood. In this study, we investigated which root trait(s) drive sediment stability (resistance to lateral erosion) in two marsh species with an important role in coastal protection (Spartina anglica and Atriplex portulacoides) and how the environment affects the expression of these traits. We sampled three marshes along salinity gradients in each of two estuaries in Wales (UK), establishing replicate plots in the respective dominant zones of each species. In all plots we sampled abiotic variables (sand, redox potential, pH, salinity) and root traits (root density, specific root density, root volume, root length density); in a subset of these plots (three per species in each marsh) we extracted soil-plant cores and assessed their erosion resistance in a flume. Sediment stability was enhanced by increases in root density and reductions in sand content. Abiotic variables affected root density in different ways depending on species: in S. anglica, redox was the only significant factor, with a positive, linear effect on root density; in A. portulacoides, redox had a non-linear (U-shaped) effect on root density, while sand had a negative effect. Collectively, these results show that (i) intraspecific variability in root density can influence sediment stability in salt marshes, and (ii) sediment properties not only influence sediment stability directly, but also indirectly via root density. These results shed light on spatial variability in the stability of salt marshes to lateral erosion and suggest that root density should be incorporated into coastal vegetation monitoring programs as an easy-to-measure root trait that links the environment to sediment stability and hence to the function and services provided by marshes.

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Tomato rooting patterns, yield and fruit quality were evaluated in a field trial where three irrigation regimes [0.6 (DI), 0.9 (DII) and 1.2 ET c (DIII)] and three drip irrigation depths [surface (R0), subsurface at 20 cm depth (RI) and subsurface at 40 cm depth (RII)] were imposed following a split-plot experimental design, with four replications. The behaviour of the root system in response to the irrigation treatments was evaluated using minirhizotrons installed between two plants, near the plant row. Rootlength intensity (L a)-length of the root per unit of minirhizotron surface area (cm cm À2)-was measured at four crop stages. For all sampling dates, none of the factors studied were found to influence L a or rooting depth significantly or the interaction between treatments. For all treatments most of the root system was concentrated in the top 40 cm of the soil profile, where the root-length density ranged from 0.5 cm cm À3 to 1.4 cm cm À3. The response of tomato fruits to an increase in the water applied was similar in quantitative and qualitative terms for the different drip irrigation depths. Water applied by drip irrigation had the opposite effect on commercial yield (t ha À1) and soluble solids (°Brix) (r=À0.82, P<0.001), however, yield in terms of total soluble solids (t ha À1) was the same for the 0.9 and 1.2 ET c. The increase in commercial yield can be described by the equation ðcommercial yield ¼ À91:106ð%ET 2 c Þ þ 264:34ð%ET c ÞÀ 55:973; R 2 ¼ 0; 63;

Drought stress is the major constraint to rice (Oryza sativa L.) production and yield stability in rainfed ecosystems. Identifying genomic regions contributing to drought resistance will help develop rice cultivars suitable for rainfed regions through molecular marker assisted breeding. Quantitative trait loci (QTLs) linked to plant water stress indicators, phenology and production traits under irrigated and drought stress conditions were mapped by means of a doubled‐haploid (DH) population of 154 rice lines from the cross CT9993‐5‐10‐1‐M/IR62266‐42‐6‐2. The DH lines were subjected to water stress before anthesis in three field experiments at two locations. The DH lines showed significant variation for plant water stress indicators, phenology, plant biomass, yield and yield components under irrigated control and water stress. A total of 47 QTLs were identified for various plant water stress indicators, phenology, and production traits under control and water stress conditions in the...

Previous studies relating root systems and drought tolerance in oil palm focused mainly on biomass. Yet, total root length (TRL), total root surface area (TRS), and root distribution in the soil better determine water uptake. These morphological traits were studied on 3 oil palm genotypes displaying a contrasting drought tolerance. A new concept of potential root water extraction ratio (PRER) was developed using measured half-distances between roots and some assumptions about the distance of water migration from soil to root. PRER was determined in conjunction with soil moisture extraction efficiency (SMEE). The presumed tolerant genotype (T) had higher TRL, TRS and PRER than the susceptible genotype (S), whilst the performance of the control genotype (I) was intermediate. Surprisingly, during a period of moderate water deficit, T had a lower SMEE than S, which was interpreted successfully with PRER, as the result of a better access to a large volume of soil and of a slower drying out of the soil around the roots. PRER appears as a helpful indicator for comparing or ranking genotypes, and for addressing better the complexity of the genetic variability of drought tolerance. Keywords Benin. Drought tolerance. Elaeis guineensis. Root biomass. Root length density. Soil moisture extraction efficiency Abbreviations df degrees of freedom Et i root water extraction per soil layer i between two dates (cm 3 d-1)

The information of soil compaction effects on growth and yield of crops for saline and waterlogged soils is scanty. A pot experiment was conducted on a sandy clay loam soil during 2001-2002 to study the interactive effects of soil compaction, salinity and waterlogging on grain yield and yield components of two wheat (Triticum aestivum) genotypes (Aqaab and MH-97). Compaction was achieved at 10% moisture level by dropping 5 kg weight, controlled by a tripod stand for 20 times from 0.6 m height on a wooden block placed inside the soil filled pots. Soil bulk density of non-compact and compact treatments was measured as 1.21 and 1.65 Mg m −3 , respectively. The desired salinity level (15 dS m −1) was developed by mixing the required amount of NaCl in soil before filling the pots. Waterlogging was developed by flooding the pots for 21 days both at tillering and booting stages. Compaction aggravated the adverse effect of salinity on grain yield and different yield components of both the wheat genotypes. Average reduction in grain yield was 44% under non-compact saline conditions against 76% under compact saline conditions. Similarly, the reduction was about 20% more for 100 grain weight and shoot length, 30% more for number of spikelets per spike, 37% more for number of tillers per plant, and 32% more for straw weight in compact saline treatment than in non-compact saline treatment. Compaction alone caused a reduction of 36% in grain yield. The effect of waterlogging on grain yield and yield components was mostly not changed significantly due to compaction. Rather waterlogging mitigated the effect of compaction for most of the yield components except for number of spikes per plant. Therefore, as for normal soils, the cultivation of salt-affected soils should employ implements and techniques which minimize compaction of root zone soil. The effect of soil compaction can also be minimized by light irrigations with short intervals and by using a stress tolerant crop genotype.

Florida is the largest producer of fresh-market tomatoes in the United States. Production areas are typically intensively managed with high inputs of fertilizer and irrigation. The objectives of this 3-year field study were to evaluate the interaction between N-fertilizer rates and irrigation scheduling on yield, irrigation water use efficiency (iWUE) and root distribution of tomato cultivated in a plastic mulched/drip irrigated production systems. Experimental treatments included three irrigation scheduling regimes and three N-rates (176, 220 and 230 kg ha À1). Irrigation treatments included were: (1) SUR (surface drip irrigation) both irrigation and fertigation line placed right underneath the plastic mulch; (2) SDI (subsurface drip irrigation) where the irrigation line was placed 0.15 m below the fertigation line which was located on top of the bed; and (3) TIME (conventional control) with irrigation and fertigation lines placed as in SUR and irrigation being applied once a day. Except for the ''TIME'' treatment all irrigation treatments were controlled by soil moisture sensor (SMS)-based irrigation set at 10% volumetric water content which was allotted five irrigation windows daily and bypassed events if the soil water content exceeded the established threshold. Average marketable fruit yields were 28, 56 and 79 Mg ha À1 for years 1-3, respectively. The SUR treatment required 15-51% less irrigation water when compared to TIME treatments, while the reductions in irrigation water use for SDI were 7-29%. Tomato yield was 11-80% higher for the SUR and SDI treatments than TIME where as N-rate did not affect yield. Root concentration was greatest in the vicinity of the irrigation and fertigation drip lines for all irrigation treatments. At the beginning of reproductive phase about 70-75% of the total root length density (RLD) was concentrated in the 0-15 cm soil layer while 15-20% of the roots were found in the 15-30 cm layer. Corresponding RLD distribution values during the reproductive phase were 68% and 22%, respectively. Root distribution in the soil profile thus appears to be mainly driven by development stage, soil moisture and nutrient availability. It is concluded that use of SDI and SMS-based systems consistently increased tomato yields while greatly improving irrigation water use efficiency and thereby reduced both irrigation water use and potential N leaching.

In this study, we describe earthworm communities along an elevation gradient of eight forest types in Northeastern Puerto Rico, and determine whether their abundance, biomass and/or diversity is related to climatic, soil physical/chemical and/or biotic characteristics. We found that the density, biomass, and diversity of worms varied significantly among forest types. The density of earthworms was highest in the Pterocarpus forest. In terms of biomass, both elfin and the Pterocarpus forests had the highest values. The number of earthworm species significantly increased as elevation and annual rainfall increased and air temperature decreased. We conclude that differences in earthworm species richness along this elevation gradient may be due to a combination of biotic and soil physical and chemical factors. Soil pH and root length density are important predictors of number of worm species along this elevation gradient.

Tillage systems affect soil properties, crop growth and nutrient uptake under various agro-ecological conditions. The uptake of water and nutrients are largely dependent on the root systems of wheat (Triticum aestivum L.) and rice (Oryza sativa L.). The application of manure has direct influence on the nutrient uptake by the crop plants. A 2 year field experiment was conducted to evaluate the impact of tillage and farm manure on root growth by measuring the root length density on a sandy clay loam (Typic calciargid soil). Three tillage systems were used; (i) minimum tillage (MT), (ii) deep tillage (DT) and (iii) conventional tillage (CT). Three farm manure levels were used; (i) FM 0 (only chemical fertilizers), (ii) FM 15 (farm manure at 15 Mg ha À1) and (iii) FM 30 (farm manure at 30 Mg ha À1). The incorporation of farm manure into soil markedly improved the root length density (RLD) of both wheat and rice crops. For wheat, the application of FM 30 increased RLD by 16% and 9% in cases of deep tillage and minimum tillage, respectively. For rice, the increase in RLD at the same farm manure rate (FM 30) was 13% and 17%, during first and second year, respectively. Averaged across tillage, the trend of RLD for both wheat and rice was DT > CT > MT. The incorporation of FM has increased the uptake of N, P and K significantly (P < 0.05), thereby increasing the agronomic parameters. The manure may be used to ameliorate the deleterious effects of tillage for sustainable crop yield.

Increasing drought resistance and nutrient availability to the plant is important for increasing yields in rainfed lowland rice. This study investigated the effects of crop establishment and controlled-release fertilizers on drought stress responses and nitrogen uptake of rice (Oryza sativa L.) cv. PSBRc14 grown on a clayey loam Vertic Tropaquept in a split-split-plot ®eld experiment. The main plots were two water treatments (well-watered and drought-stressed for 20 days from panicle initiation). The subplots comprised of three crop establishment methods. In the sub-subplots, prilled urea was compared with Polyon 12 and POC-S120. Drought prolonged crop maturity by about 20 days and greatly reduced grain yield but not the total biomass and total N uptake. Dry-seeded rice had a lower yield in the well-watered treatment but higher yield in the stress treatment compared with transplanted and wet-seeded rice. The higher yield of dry-seeded rice under stress could be related to its signi®cantly higher root length density, higher root±shoot ratio, and more uniform root distribution with respect to soil depth, and higher available soil moisture in the root zone during the stress period. Under the well-watered condition, yields in all fertilizer treatments were comparable. In the stress treatment, Polyon 12 produced the lowest yield probably because of the mismatch between drought-induced prolongation of crop duration and the release period of Polyon 12.

In this study, we describe earthworm communities along an elevation gradient of eight forest types in Northeastern Puerto Rico, and determine whether their abundance, biomass and/or diversity is related to climatic, soil physical/chemical and/or biotic characteristics. We found that the density, biomass, and diversity of worms varied significantly among forest types. The density of earthworms was highest in the Pterocarpus forest. In terms of biomass, both elfin and the Pterocarpus forests had the highest values. The number of earthworm species significantly increased as elevation and annual rainfall increased and air temperature decreased. We conclude that differences in earthworm species richness along this elevation gradient may be due to a combination of biotic and soil physical and chemical factors. Soil pH and root length density are important predictors of number of worm species along this elevation gradient.

Conservation tillage practices, such as reduced tillage and no-tillage, have recently garnered significant attention as core elements of the regenerative agriculture and carbon farming concepts. By minimizing mechanical soil disturbance, these practices preserve soil carbon and facilitate CO2 fixation in the soil. Despite the widely acknowledged benefits, many farmers still approach no-tillage with skepticism. Their primary concerns are weed management and soil compaction. While weeds can be effectively controlled with the deployment of integrated weed management strategies, urgent soil compaction problems can be rapidly resolved only with mechanical interventions. That is why many no-till farmers resort to occasional heavy tillage, in a scheme characterized as rotational tillage, inadvertently sacrificing their regenerative assets in soil carbon. This is also a pivotal issue within carbon farming: the fate of soil carbon at the end of a compliant scheme focused on carbon fixation. ...

C limatic changes and the need to reduce water consumption for irrigation have led to broader use of watereffi cient turfgrass species such as warm-season grasses. Turfgrass management is extremely complex in transition zone areas, where temperatures and moisture have a large infl uence on the species adaptability. In these zones, climate can present opposite conditions through the year, with mild, rainy winters and hot, dry summers (Geren et al., 2009). Th ese extreme conditions can signifi cantly impact the selection of appropriate turfgrasses and growing media (Croce et al., 2001). Turfgrasses are commonly classifi ed in two diff erent groups, based on their photosynthetic pathway, but more importantly, based on the period of the year with the highest vegetative growth. Cool-season grasses, which use the C3 photosynthetic pathway, have lower drought tolerance and water use effi ciency compared to warm-season grasses, and suff er from heat stress when temperatures exceed 32°C. Warm-season grasses have good drought resistance and are more active during the summer, when temperatures are usually between 26 and 35°C (Unruh et al., 1996). Instead, excessive cold weather and frozen soil can cause injuries to perennial stands of these turfgrasses and lead to extended winter dormancy periods. Maintaining cool-season grasses in temperate or transitional climate zones has been criticized because of the relatively high irrigation requirements during the summer (Croce et al., 2001; Huang, 2008; Rimi et al., 2011). As a result, the use of warm-season turf species that require less water is encouraged to reduce water consumption for landscape irrigation (Macolino et al., 2010; Schiavon et al., 2012). Warm-season turfgrasses also generally have a higher resistance to fungal diseases and traffi c stress in comparison to the cool-season species (Puhalla et al., 1999). Despite these positive aspects, turfgrass managers and home lawn owners are oft en hesitant to use warm-season turfgrasses in the transition zone because of their long winter dormancy (Richardson, 2002). Dormancy consists of a physiological rest followed by leaf desiccation, resulting in reduced or no color (Rimi et al., 2013), which can persist for several months during the winter. Although warm-season turfgrasses may not provide active growth and green color during the cooler months, they can still successfully provide ground cover and erosion control (Anderson et al.,

A field experiment was carried out at ICAR-Indian Agricultural Research Institute, New Delhi during kharif 2015 and 2016 to determine the effects of rice establishment method, silicon application levels and silicon solubilizing bacteria on silicon concentrations and uptake by rice (Oryza sativa) and soil microbial parameters in rice-wheat cropping system. The experiment was laid out in split-split plot design and replicated thrice. The experiment was conducted with 24 treatment combinations including rice establishment methods in main plot, silicon level in sub plot and silicon solubilizing microbes in sub-sub plot. Silicon concentration in grain and straw was highest in crop establishment of aerobic rice and lowest in TPR methods during both the years. Tested aerobic rice establishment methods significantly influenced the microbial biomass carbon (278.2 and 289.3 μg/g soil), soil dehydrogenase activity (202.3 and 198.3 µg TPF/g soil/day) and total count of silicon solubilizing bacteria (222.5 and 255.9 × 10 2 cfu/g soil) compared to SRI and TPR and the highest silicon concentration and uptake, microbial biomass carbon (285.9 μg/g soil), dehydrogenase activity (189.7 µg TPF/g soil/day) and total count of silicon solubilizing bacteria (239.6 10 2 cfu/g soil) was recorded with silicon application 120 kg/ha which at par with 80 kg/ha but statistically superior over to control and 40 kg/ha in terms of nutrient uptake in grain and straw and soil quality parameters during both years of study.

Tree root systems stabilize hillslopes and riverbanks, reducing landslide risk, but related data for the humid tropics are scarce. We tested fractal allometry hypotheses on differences in the vertical and horizontal distribution of roots of trees commonly found in agroforestry systems and on shear strength of soil in relation to root length density in the topsoil. Proximal roots of 685 trees (55 species; 4–20 cm stem diameter at breast height, dbh) were observed across six landscapes in Indonesia. The Index of Root Anchoring (IRA) and the Index of Root Binding (IRB) were calculated as ΣDv2/dbh2 and as ΣDh2/dbh2, respectively, where Dv and Dh are the diameters of vertical (angle &gt; 45°) and horizontal (angle &lt; 45°) proximal roots. High IRA values (&gt;1.0) were observed in coffee and several common shade trees. Common fruit trees in coffee agroforestry had low medium values, indicating modest ‘soil anchoring’. Where root length density (Lrv) in the topsoil is less than 10 km m−3...

Cocoa is one of the agricultural commodities that have important role and are reliable in realizing agricultural development program of Indonesia. The cocoaproduction of Indonesia tends to decrease that caused by in appropriate farming. This research aimed to evaluate the shade management to cocoa productivity and evaluating the correlation between soil quality and the cocoa production with the different shade management. This research was conducted from October 2016 until June 2017 in Kaliwining Experimental Station and Soil Laboratory of Indonesian Coffee and Cocoa Research Institute (ICCRI), Jember, Indonesia. Clones at the trial plots were Sulawesi 1 and Sulawesi 2, 10 years old, and arranged in 3 m x 3 m spacing. The design of this research was conducted by observing parameters of sample trees on cocoa field. This research used three observation plots, with shade trees of leucaena (Leucaena sp.), teak (Tectona grandis), and teak combined with krete (Cassia surithensis) shade. T...

The purpose of this study was to determine how a plant's response to colonization by mycorrhizal fungi relates to its ability to acquire and utilize phosphorus for growth and reproduction. Two tomato genotypes previously found to be either responsive (' LA1709 ') or unresponsive (' large cherry ') to mycorrhizal colonization during early vegetative growth were examined in detail. Plants were grown at four levels of added phosphate or with mycorrhizal inoculum. Vegetative and reproductive growth, phosphorus uptake and root length density were measured during the course of plant development. Mycorrhizal symbiosis significantly increased above-ground dry mass, root length, phosphorus content and yield under low phosphorus conditions in ' LA1709 ', while it had less effect on these characteristics in ' large cherry '. When uninfected, however, ' LA1709 ' grew and reproduced poorly unless high amounts of phosphorus were added to the soil, while ' large cherry ' grew well under very low phosphorus conditions. This was because ' large cherry ' had significantly higher root length densities than ' LA1709 ', enabling plants from this genotype to explore more soil volume and acquire greater amounts of phosphorus when grown without mycorrhizal fungi in low phosphorus soil. ' Large cherry ' also had higher phosphorus use efficiency and allocated a greater proportion of phosphorus to reproduction when uninfected than ' LA1709 '. It appears traits that affect a plant's ability to acquire and utilize phosphorus efficiently for growth and reproduction can also affect its response to mycorrhizal colonization in tomato.

Root growth at soil depths below 30 cm may provide access to critical soil water reserves during drought in rainfed lowland rice. In this study, the OryzaSNP panel, a set of 20 lines representing genetic diversity in rice used for the discovery of DNA sequence polymorphisms, was evaluated for root characteristics in the field over three seasons varying in drought severity. Root length density (RLD) at a depth of 30-45 cm varied up to 74-92% among genotypes under drought stress (2008-2009 dry seasons), ranging from 0.024 to 0.23 cm cm −3 in 2008 and from 0.19 to 0.81 cm cm −3 in 2009. Real-time monitoring of soil moisture profiles revealed significant differences among genotypes, and these differences were correlated with RLD at those soil depths. Among the lines evaluated, the Aus isozyme group, particularly the genotype Dular, showed greater drought resistance associated with deep root growth and the highest drought response index (less reduction in yield by drought stress). Since the set of genotypes used in this study has been completely sequenced for SNP markers, the phenotypic information on root growth and drought avoidance responses presented here could be used in initial analysis of the genetic basis of dehydration avoidance traits and in facilitating improvement in drought resistance in rice.

Gas exchange was measured in potatoes (cv. Folva) grown in lysimeters (4.32 m 2) in coarse sand, loamy sand, and sandy loam and subjected to full (FI), deficit (DI), and partial root-zone drying (PRD) irrigation strategies. PRD and DI as water-saving irrigation treatments received 65% of FI and started after tuber bulking and lasted for six weeks until final harvest. Midday photosynthesis rate (A n) and stomatal conductance (g s) of fully irrigated (FI) plants were lowest in coarse sand and mean A n of diurnal measurements in FI, PRD and DI tended to be lower in this soil as compared with the loamy sand and sandy loam. The results revealed that diurnal values of A n and g s in PRD and DI were consistently lower than FI without reaching significant differences in accordance with findings that xylem [ABA] in PRD was significantly higher than FI, and tended to be higher than in DI. Diurnal measurements showed that A n reached peak values during mid-morning and midday, while g s were highest during the morning. Intrinsic water use efficiency (A n /g s) correlated linearly well with the leaf to air vapor pressure deficit (VPD) and the slope of the line revealed the rate of A n /g s increase per each kPa increase in VPD, i.e. approximately 10 mol mol −1. Transpiration efficiency (A n /T) of PRD was higher than DI, which shows slightly better efficient water use than DI. The slope of the linear relationship between transpiration efficiency and VPD decreased from −2.03 to −1.04 during the time course of the growing season, indicating the negative effect of leaf ageing on photosynthesis and thus on plant water use efficiency. This fact shows the possibility to save water during last growth stages through applying water-saving irrigations without much effect on transpiration efficiency.

Traits related to nitrogen fixation may be used as indirect selection criteria for aflatoxin resistance in peanut. The aim of this study was to investigate the relationship between N 2 fixation traits and aflatoxin contamination in peanut under different drought conditions. Eleven peanut genotypes were evaluated under three water regimes for two seasons in the field. Data were observed on kernel infection by Aspergillus flavus, aflatoxin contamination, total nitrogen content, N 2 fixation and its related traits viz. nodule number, nodule dry weight and nitrogenese activity. Drought stress reduced total nitrogen content and N 2 fixation, but it increased kernel infection and aflatoxin contamination. Total nitrogen content, N 2 fixation and its related traits had negative and significant effects on kernel infection and aflatoxin contamination especially under drought conditions. In addition, negative correlations between kernel infection and aflatoxin contamination with drought tolerance index (DTI) of N 2 fixation traits were also found. The results indicated that the ability to maintain high N 2 fixation under drought conditions of peanut genotypes can result in better resistance to aflatoxin contamination.

The establishment of stress resilient sugar beets (Beta vulgaris spp. vulgaris) is an important breeding goal since this cash crop is susceptible to drought and salinity. The genetic diversity in cultivated sugar beets is low and the beet wild relatives are useful genetic resources for tolerance traits. Three wild beet populations (Beta vulgaris spp. maritima) from contrasting environments, Vaiamonte (VMT, dry inland hill), Comporta (CMP, marsh) and Oeiras (OEI, coastland), and one commercial sugar beet (Isella variety, SB), are compared. At the genetic level, the use of six microsatellite allowed to detect a total of seventy six alleles. It was observed that CMP population has the highest value concerning the effective number of alleles and of expected heterozygosity. By contrast, sugar beet has the lowest values for all the parameters considered. Loci analysis with STRUCTURE allows defining three genetic clusters, the sea beet (OEI and CMP), the inland ruderal beet (VMT) and the s...

New strategies for sugarcane production have been very important since the incorporation of ethanol in the Brazilian energy mix in the early 1970s. Prior to planting sugarcane, the soil is prepared, and this process can affect root development and, consequently, sugarcane production. This study was conducted in an area of sugarcane crop renewal in the Cerrado biome (Brazilian tropical savanna), with the objective of identifying which tillage system generates the better root development and improved yield in sugarcane. The treatments were: 1) weed desiccation + moldboard plowing (0.4 m) + mild spike tooth harrowing (0.15 m); 2) subsoiler (0.3 m) + mild spike tooth harrowing (0.15 m); 3) weed desiccation + no-tillage (furrow opening and fertilizer); 4) weed desiccation + subsoiler (0.4 m); 5) ratoon destruction + subsoiler (0.4 m); 6) ratoon destruction + spike tooth harrowing (0.2 m) + moldboard plowing (0.4 m) + mild spike tooth harrowing (0.15 m). Characteristics of the sugarcane root system, such as the root length density, average distance between roots, and root soil exploration, after the first harvest (1.5 years) were studied. Root length density was greater for the treatments that included plowing (0.4 m) and harrowing (0.15 m) operations. The average distance between roots was low in the no-tillage system. The highest sugarcane yield in the plant crop was achieved by management practices with more extensive soil profile disturbances, like plowing followed by harrowing.

Root growth can be limited by physical and chemical conditions of the soil. Compacted and acidic soils, where there is an occurrence of exchangeable Al, constitute barriers to use of the soil by plant roots. The hypothesis of this study was that physical and chemical properties of the inter-row soil of a peach orchard influence the root distribution of different rootstocks. The aim of this study was to describe and register the soil physical and chemical properties and root distribution in the soil profile of the inter-row of seven years old mature peach (Prunus persica) orchard. Samples of soil (classified as an Argissolo Vermelho Distrófico típico [Rhodic Paleudult] with 180 g kg-1 clay, 120 g kg-1 silt, and 700 g kg-1 sand) and roots were collected from orchard inter-rows of 'Maciel' peach, grafted onto 'Okinawa' and 'Nemaguard' rootstock, at 1.5, 2.0, and 2.5 m from the trunk, and at every 0.10 m, up to a depth of 0.50 m. The soil samples were sieved and the roots washed. A subsample was removed from each sample for chemical analysis. Resistance to penetration (RP) was used as an indicator of soil compaction. A close relationship was found among chemical properties, RP, and root distribution. Root density was affected by the presence of compacted regions (RP >2,000 kPa) and by high Al saturation in the exchange complex in the soil profile. There was a reduction in the frequency of thick roots (Ø >2 mm) in the samples collected in portions of compacted soil and at increasing soil depth. The compacted portion of the inter-row limits lateral distribution of the peach tree root system, while aluminum limits its depth.

The sustainability of cool-season grasses in temperate climates (transition zones) has been questioned because of a high irrigation requirement during the summer months. To reduce the amount of water used for irrigation, warm-season turf species such as Cynodon dactylon L. and Zoysia japonica Steud. have been introduced into Mediterranean countries. Research was conducted at the University of Padova, Italy to investigate several root characteristics and turf performance of four bermudagrasses and one zoysiagrass in the transitional climate of northeastern Italy. The study included Cynodon dactylon cultivars 'Yukon', 'Riviera', 'NuMex Sahara', and 'La Paloma' and Zoysia japonica 'Companion'. Visual ratings for color and density were taken monthly during the growing season of 2007 and averaged for spring, summer, and fall. In September 2007 turf cores were collected from each plot to determine absolute values for root length density (RLD), root weight density (RWD), and root diameter in the thatch layer and at five soil depths: 0-3, 3-8, 8-15, 15-25 and 25-40 cm. Weighted means were calculated for 0-40 cm. There was no difference in RLD and RWD in the thatch layer among cultivars. 'La Paloma' had the highest RLD and RWD and 'Yukon' and 'Companion' zoysiagrass exhibited the lowest RLD and RWD for weighted means. 'Yukon' exhibited the darkest green color and 'Companion' the lightest during summer and fall. 'Yukon' and 'Riviera' provided the highest stand density and 'Companion' the lowest throughout the investigative period. Summer color correlated significantly (P<0.05) with all measured root parameters at the soil depth of 25-40 cm. Summer turf color also correlated significantly (P<0.05) with the weighted means of root length and root weight yielding correlation coefficients of 0.51 and 0.52, respectively. No correlation could be established between stand density and rooting.

Conservation tillage is a management system used to mitigate and rehabilitate the dryland areas of southerncentral Chile in severely compacted soils. The objective of this study was to evaluate the soil physical properties in the root zone under an oat-wheat crop rotation after three years of the establishment of three tillage systems: conventional tillage (CT), zero tillage (ZT) and zero tillage with subsoiling (ZTS). Soil bulk density, porosity, water retention curve, stability of macro-and microaggregates, airflow at field capacity, rest coefficient, and number of roots were evaluated. The results showed that the soil had low water holding capacity in the profile due to the low water retention at the permanent wilting point (matric water potential lower than-1.500 kPa), associated with a high bulk density and clay content. The conservation tillage systems (ZT and ZTS), were similar in the parameters of fast drainage pores (FDP), aggregate stability index, airflow, and rest coefficient compared with CT. However, the volume of pores with diameters between 10-50 μm was higher in ZTS in a 24% and 13%, compared with ZT and CT, respectively. In addition, the root development increased significantly in ZTS. In conclusion, the physical condition of the compacted soil was improved by the zero tillage system with subsoiling, which promoted a better root system in the first horizons in highly compacted soils.

In this study, we describe earthworm communities along an elevation gradient of eight forest types in Northeastern Puerto Rico, and determine whether their abundance, biomass and/or diversity is related to climatic, soil physical/chemical and/or biotic characteristics. We found that the density, biomass, and diversity of worms varied significantly among forest types. The density of earthworms was highest in the Pterocarpus forest. In terms of biomass, both elfin and the Pterocarpus forests had the highest values. The number of earthworm species significantly increased as elevation and annual rainfall increased and air temperature decreased. We conclude that differences in earthworm species richness along this elevation gradient may be due to a combination of biotic and soil physical and chemical factors. Soil pH and root length density are important predictors of number of worm species along this elevation gradient.

Acknowledgements This study is part of a large project adressing „Adaptation of African agriculture to climate change “funded by the German Ministry for collaboration and development through GTZ/BEAF. More information can be found at www. risocas. de. ...

Root growth can be limited by physical and chemical conditions of the soil. Compacted and acidic soils, where there is an occurrence of exchangeable Al, constitute barriers to use of the soil by plant roots. The hypothesis of this study was that physical and chemical properties of the inter-row soil of a peach orchard influence the root distribution of different rootstocks. The aim of this study was to describe and register the soil physical and chemical properties and root distribution in the soil profile of the inter-row of seven years old mature peach (Prunus persica) orchard. Samples of soil (classified as an Argissolo Vermelho Distrófico típico [Rhodic Paleudult] with 180 g kg-1 clay, 120 g kg-1 silt, and 700 g kg-1 sand) and roots were collected from orchard inter-rows of 'Maciel' peach, grafted onto 'Okinawa' and 'Nemaguard' rootstock, at 1.5, 2.0, and 2.5 m from the trunk, and at every 0.10 m, up to a depth of 0.50 m. The soil samples were sieved and the roots washed. A subsample was removed from each sample for chemical analysis. Resistance to penetration (RP) was used as an indicator of soil compaction. A close relationship was found among chemical properties, RP, and root distribution. Root density was affected by the presence of compacted regions (RP >2,000 kPa) and by high Al saturation in the exchange complex in the soil profile. There was a reduction in the frequency of thick roots (Ø >2 mm) in the samples collected in portions of compacted soil and at increasing soil depth. The compacted portion of the inter-row limits lateral distribution of the peach tree root system, while aluminum limits its depth.

Rice yield fluctuates because of environmental influences on morphological and physiological processes, as well as inadequate human intervention, to stabilize crop productivity. A field experiment was conducted in two cropping seasons at the experimental area of the Department of Agronomy, Visayas State University, Baybay, Leyte to evaluate the morphological and physiological performance of lowland rice grown at different water, spacing and nutrient management. Different sources of fertilizers were designated as the mainplot and plant spacing as the subplot nested within two water regimes, ie, continuous flooding and no flooding. Lowland rice s under no flooding were shorter than those under plant continuous flooding. No flooding gave higher root pulling resistance, crop growth rate, net assimilation rate, leaf area index and harvest index and consequently produced higher grain yield of PSB Rc18. No flooding and continuous flooding water management resulted in the formation of aeren...

Rht-B1 is one of the most important genes responsible for the height of bread winter wheat (Triticum aestivum L.). Studies of dwarfing genes are crucial for both improving genetic potential of the bread wheat cultivar and developing new effective breeding strategies in conditions of insufficient moisture. In this study, tall isogenic lines containing wild type Rht-B1a allele (Odes'ka 267 and Odes'ka 51) and short ones containing Rht-B1b (Odes'ka 267 b) and Rht-B1e (Odes'ka 51 e) alleles was analysed. The aim of the experiment was to evaluate direct and pleiotropic effects of these alleles on main agronomic traits of winter wheat in the south steppe region of Ukraine. Methods used are allele-specific PCR, polyacrylamide gel electrophoresis (PAGE), structural analysis of main agronomic traits and statistical data processing. Effects of Rht-B1b and Rht-B1e alleles on important agronomic characteristics of winter wheat were evaluated and were found differences in their influence on such traits: plant height, thousand kernel weight, total protein content, absolute protein content of thousand kernels. Rht-B1e reduces plant height more dramatically than Rht-B1b: decrease in plant height was 40.0% and 17.6%, respectively. The negative effects of Rht-B1e are decline in number of fertile spikelets, number and weight of kernels in the main ear, thousand kernel weight, whereas in plants with Rht-B1b these traits were increased, compared to the Rht-B1a allele plants. Main spike density was decreased by both alleles, but for Rht-B1e the drop was bigger. Rht-B1e more essentially increased productive tillering than Rht-B1b. In drought conditions plants with Rht-B1e allele showed less productivity than those containing Rht-B1b compared to respective recurrent wild type allele lines.

Com o objetivo de avaliar a capacidade de crescimento de raízes em camadas de solo compactadas, quatro espécies de plantas de cobertura (amaranto, milheto ADR 500, capim pé-de-galinha e kenaf) foram cultivadas em anéis de PVC, com níveis de compactação em subsuperfície (densidade do solo: 1,18; 1,34; 1,51 e 1,60 Mg m-3), sendo o experimento conduzido em casa de vegetação, utilizando-se de um Latossolo Vermelho distroférrico. A camada compactada em subsuperfície foi restritiva ao crescimento de raízes das espécies estudadas, ocasionando a concentração de raízes na camada superficial. O milheto ADR 500 e o amaranto foram as espécies que se destacaram na produção de massa seca da parte aérea e conseguiram desenvolver-se nas camadas compactadas e abaixo delas. O milheto ADR500 apresentou maior densidade de comprimento radicular em todas as camadas. O capim pé-de-galinha e o amaranto tiveram comportamento semelhante quanto à densidade de comprimento radicular. O capim pé-de-galinha e o k...

The critical K concentration in soybean [Glycine max (L.) Merr.] has been determined only for leaf tissue at the R2 (full bloom) stage. Our research objective was to develop critical K concentrations in soybean for both leaves and petioles across reproductive stages. Fifteen fully-expanded, uppermost trifoliolate leaves with petioles plot-1 were collected 7 to 12 times from the V5 to R7 stages in five research trials that evaluated multiple fertilizer-K rates and/or cultivars from different maturity groups (MGs). Both leaf-and petiole-K concentrations, regardless of site-year, cultivar, and fertilizer-K rate, peaked around R2 stage and declined linearly with time at average rates of-0.198 g K kg-1 d-1 for leaves and-0.559 g K kg-1 d-1 for petioles. The leaf-and petiole-K concentrations at the R2 to R6 stages explained 48 to 80% and 41 to 85%, respectively, of the variation in relative yield (RY). Petiole-K concentration was a better predictor of RY than leaf-K at the R2 stage where the predicted critical range (CR) concentrations were 14.6 to 19.0 g leaf-K kg-1 and 30.1 to 38.3 g petiole-K kg-1. The wider CR of petiole-K at the R2 stage followed by a greater linear decline rate across reproductive stages indicates that growth stage as well as deficiency and sufficiency thresholds for petiole-K could be more easily categorized than for leaves. Overall, the ability to interpret the K nutritional status in soybean tissues at numerous reproductive growth stages will improve K management.

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Soil Fertility & Plant Nutrition soybean [Glycine max (L.) Merr.] seed nutrient concentrations may be useful for postseason diagnosis of nutrient deficiencies to identify reasons for lower-than-expected yields. Our objective was to determine the relationships between seed-K and soil-K concentrations and relative soybean yield and to develop potential seed-K concentration thresholds for diagnosis of K deficiency as a yield-limiting factor. soil-test K and seed-K concentrations and yield data were collected from published and unpublished K fertilization research conducted in Arkansas (33 site-years), Indiana (1 site-year), Iowa (34 site-years), Missouri (1 site-year), Tennessee (6 site-years), Virginia (1 site-year), and Canada (24 site-years). seed-K concentrations accounted for 66% of the variation in relative yield of soybean receiving no fertilizer K for Arkansas, 48% for Iowa, 78% for Canada, and 60% for North America from a database that included 100 site-years. The critical seed-K concentration ranges were 15.6 to 17.0 g K kg −1 for Arkansas, 17.4 to 20.0 g K kg −1 for Iowa, 14.6 to 16.2 g K kg −1 for Canada, and 16.5 to 17.7 g K kg −1 for North America. seed-K concentrations below the lower threshold for North America accurately predicted positive yield responses to fertilizer K at 77% of the sites classified as deficient. The difference between seed-K concentration of soybean grown with and without fertilizer K decreased linearly as soil-K concentration increased and plateaued when soil-K concentration was ³87, 139, 73, and 104 mg K kg −1 for Arkansas, Iowa, Canada, and North America, respectively. Results suggest that seed-K concentrations can be used to aid in the diagnosis of K deficiency at maturity.

The cultivation systems of sugarcane can cause changes to the soil's physical properties and root development, which in turn, can affect the productivity of the crop. The main objective of this study was to evaluate different soil management systems and their influence on the physical attributes of soil, plant root system development and the productivity of plant cane in re-established area. The experimental design was randomized blocks in 6 x 3 factorial scheme with 4 repetitions. The soil treatments were: T 1 = Desiccation + moldboard plowing + light harrow (DPH); T 2 = Subsoiler + light harrow (SH); T 3 = Desiccation + no-tillage (DNT); T 4 = Desiccation + subsoiler (DS); T 5 = stubble thrasher + subsoiler (StS) and T 6 = stubble thrasher + mid harrow + moldboard plow + light harrow (StHPH), each evaluated at three depths (0.0-0.20; 0.20-0.40 and 0.40-0.60 m). The effects of these treatments were evaluated by analyzing physical properties of soil, root development of the plants and productivity of the crop. All evaluated tillage systems improved penetration resistance, but only to the depth of 0.20 m. The best rates of root development occurred with the T1 treatment. Root development was significantly lower with higher penetration resistance values in all evaluated systems. Sugarcane productivity was significantly higher in systems with greater soil disturbance.

Excessive evaporative loss of water from the topsoil in arid-land agriculture is compensated via irrigation, which exploits massive freshwater resources. The cumulative effects of decades of unsustainable freshwater consumption in many arid regions are now threatening food-water security. While plastic mulches can reduce evaporation from the topsoil, their cost and nonbiodegradability limit their utility. In response, we report on superhydrophobic sand (SHS), a bio-inspired enhancement of common sand with a nanoscale wax coating. When SHS was applied as a 5 mm-thick mulch over the soil, evaporation dramatically reduced and crop yields increased. Multi-year field trials of SHS application with tomato (Solanum lycopersicum), barley (Hordeum vulgare), and wheat (Triticum aestivum) under normal irrigation enhanced yields by 17%-73%. Under brackish water irrigation (5500 ppm NaCl), SHS mulching produced 53%-208% higher fruit yield and grain gains for tomato and barley. Thus, SHS could benefit agriculture and city-greening in arid regions.

Excessive evaporative loss of water from the topsoil in arid-land agriculture is compensated via irrigation that exploits massive freshwater resources. The cumulative effects of decades of unsustainable freshwater withdrawals in many arid regions are now threatening food−water security. While plastic mulches can reduce evaporation from the topsoil, their cost and nonbiodegradability limit their utility. In response, we report on biodegradable superhydrophobic sand (SHS), a bioinspired enhancement of common sand with a nanoscale wax coating. When SHS was applied as a 5−10 mm-thick mulch over the soil, evaporation was reduced by 56−78% and soil moisture increased by 25−45%, which benefited the development of crops. Multiyear field trials with tomato (Solanum lycopersicum), barley (Hordeum vulgare), and wheat (Triticum aestivum) under normal irrigation demonstrated that SHS mulch application enhanced yields by 17−73%. Under brackish water irrigation (5500 ppm NaCl), SHS mulching produced 53−208% higher fruit and grain yields for tomato and barley crops, respectively. SHS application did not affect the soil−root−rhizosphere microbial communities as evidenced by 16S rRNA gene analysis. The rhizospheric environments were dominated by an assemblage of diverse bacterial communities, such as Gammaproteobacteria, Alphaproteobacteria, and Bacteroidetes, followed by Firmicutes, Gemmatimonadetes, and Actinobacteria, which could be responsible for the degradation of paraffin wax on the SHS. Thus, SHS technology should benefit irrigated agriculture and city-greening efforts in arid regions under the constraint of high water-use efficiency.

Field experiment was conducted at the teaching and Research Farm, Ladoke Akintola University of Technology, Ogbomoso and Niger State College of Agriculture, Mokwa, in 2014 cropping season to examine the effects of mulching on growth and fruit yield of UC82B tomato variety. The experiment had fifteen treatments viz: three mulching materials (rice husk, groundnut shell and dry guinea grass) and five mulching rates (0, 5, 10, 15, and 20 in t ha-1) replicated three times. The experiment was laid out in Randomized Complete Block Design (RCBD) and data were collected on plant height, number of leaves, number of flowers, number of fruits and total fruit yield. Data were analysed using analysis of variance (ANOVA) SAS package and treatment means compared using least significant difference (LSD) at 5% probability level. The results indicated that plants mulched with 15 t ha-1 at 6 weeks after transplanting gave the tallest plant height (39.9 cm) and the least was obtained from the control pl...

Belowground plant biomass plays a critical role in the maintenance of riparian ecosystems and generally constitutes the majority of the total biomass on a site. Despite this importance, belowground dynamics of riparian plant species are not commonly investigated, in part because of difficulties of sampling in a belowground riparian environment. We investigated the field utility of a root-ingrowth sampling technique for measuring root production. We established four streamside sampling sites in southeastern Oregon, and randomly located four plots within each site. In each plot we established two 7.6-cm-diameter sandfilled ingrowth cores in September of 2004. In September of 2005 we harvested the cores with the use of a vacuum sampling technique in which a 5.1-cm-diameter camphored polyvinyl chloride casing was driven into the center of the root core and sand and root materials were suctioned out. Root-length density was determined by computer image analysis, and roots were dried and weighed to determine production by weight. Results indicate that root-length density averaged 7.2 (6 0.7) cm ? cm 23 across sites and root-production index was 356.7 (6 20.6) g ? m 22. Our index to root production by weight was consistent with previous estimates of annual root production reported in the literature. Our sampling technique proved to be a practical solution for root sampling in riparian environments, and helps overcome some of the difficulties in sequential coring of saturated soils. Use of any ingrowth core technique to index root production can potentially bias production estimates because of the artificial, root-free environment of the core. However, these biases should be consistent across sites, making ingrowth cores useful for determining differences between manipulative treatments. Resumen La biomasa subterránea de las plantas tiene papel crítico en el mantenimiento de ecosistemas rivereñ os y generalmente constituye la mayor parte de la biomasa total de un sitio. A pesar de esta importancia, las dinámicas debajo del suelo de las especies de plantas rivereñ as, normalmente no se investigan, en parte por las dificultades de muestreo bajo el suelo en un ambiente rivereñ o. Investigamos la utilidad de campo de una te´cnica de muestreo de crecimiento de raíz para medir la producción de la misma. Establecimos cuatro sitios de muestreo a la orilla del torrente al sureste de Oregón, con cuatro parcelas al azar en cada sitio. En cada parcela establecimos dos núcleos de crecimiento de 7.6 cm de diámetro rellenos de arena en septiembre del 2004. En septiembre del 2005 cosechamos los núcleos utilizando una técnica de muestreo al vacio donde una cubierta de PVC de 5.1 cm de diámetro se introdujo en el centro de núcleo de la raíz, y la arena y los materiales de la raíz se succionaron hacia afuera. La densidad de la longitud de la raíz se determinó por análisis de imagen computacional. Además, las raíces se secaron y pesaron para determinar la producción por medio del peso. Los resultados indican que la densidad de la longitud de la raíz promedió 7.2 (6 0.7) cm ? cm 3 a trave´s de los sitios y el índice de producción de la raíz fue 356.7 (6 20.6) g ? m 2. Nuestro índice de producción de raíz por peso fue consistente con previas estimaciones de producción anual de raíces reportadas en la literatura. Nuestra te´cnica de muestreo probó ser una solución práctica para muestreo de raíz en ambientes rivereñ os y ayudó a vencer algunas de las dificultades en secuencias básicas de suelos saturados. El uso de cualquier te´cnica de núcleo creciente para el índice de producción de raíz puede potencialmente perjudicar las estimaciones de producción debido al ambiente artificial libre de raíces del núcleo. Sin embargo, esas tendencias deben ser consistentes a trave´s de los sitios, haciendo que los núcleos de crecimiento sean útiles para determinar las diferencias entre tratamientos manipulativos.

Improved or planted fallows using fast-growing leguminous trees are capable of accumulating large amounts of N through biological N 2-fixation and subsoil N capture. During the fallow phase, the cycling of nutrients is largely efficient. However, there are few estimates of the fate of added N during the cropping phase, after the 'safety net' of fallow-tree roots is removed. Nitrate-N at the end of the fallow phase, which is pre-season to the subsequent crop, was monitored in seven land use systems in successive 20-cm soil layers to 120 cm depth at Domboshawa, Zimbabwe in October 2000. Thereafter, nitrate-N dynamics was monitored during cropping phase until April 2001 at 2-week intervals in plots that had previously 2-year planted fallows of Acacia angustissima and Sesbania sesban, and in a continuous maize control. Pre-season nitrate concentrations below 60 cm soil depth were <3 kg N ha −1 layer −1 for S. sesban, A. angustissima, Cajanus cajan and natural woodland compared with the maize (Zea mays L.) control, which had >10 kg N ha −1 layer −1. There was a flush of nitrate in the S. sesbania and A. angustissima plots with the first rains. Topsoil nitrate had increased to >29 kg N ha −1 by the time of establishing the maize crop. This increase in nitrate in the topsoil was not sustained as concentrations decreased rapidly due to leaching. Nitrate then accumulated below 40 cm, early in the season when maize root length density was still low (<0.1 cm cm −3) and inadequate to effectively intercept the nitrate. It is concluded that under light soil and high rainfall conditions, there is an inherent problem in managing nitrate originating from mineralization of organic materials as it accumulates at the beginning of the season, well ahead of peak demand by crops, and is susceptible to leaching before the crop root system develops.