Abstract. A knowledge of spatio-temporal variability in potential yield is essential for site-spe... more Abstract. A knowledge of spatio-temporal variability in potential yield is essential for site-specific nutrient management in crop production. The objectives of this project were to develop a model for photosynthetically active radiation (PAR) intercepted by almond and walnut trees based on data obtained from respective tree(s) and estimate potential crop yield in individual trees or in blocks of five trees. This project uses proximally sensed PAR interception data measured using a lightbar mounted on a mobile platform and a crop growth model to estimate potential yields of almond and walnut trees. An analytical model was developed to estimate PAR intercepted by the tree in which tree canopy was assumed to be spherical in shape. PAR intercepted by a tree was estimated taking into account the effect of row spacing, tree spacing within the row, latitude and longitude of the orchard, day of the year and row orientation. Scans were collected at solar noon in almond and walnut orchards during the 2012 and 2013 growing seasons. Moreover, diurnal scans were also collected during 2012. Actual yield from those trees with lower values of midday PAR interception was found to be closer to their respective potential yield than those trees with higher values of midday PAR interception. These results suggest that there is a potential to use spatially variable PAR interception data to implement site-specific input management and enhance production.
Background and Aims Photosynthetic radiation use ef®ciency (PhRUE) over the course of a day has b... more Background and Aims Photosynthetic radiation use ef®ciency (PhRUE) over the course of a day has been shown to be constant for leaves throughout a general canopy where nitrogen content (and thus photosynthetic properties) of leaves is distributed in relation to the light gradient. It has been suggested that this daily PhRUE can be calculated simply from the photosynthetic properties of a leaf at the top of the canopy and from the PAR incident on the canopy, which can be obtained from weather-station data. The objective of this study was to investigate whether this simple method allows estimation of PhRUE of different crops and with different daily incident PAR, and also during the growing season. d Methods The PhRUE calculated with this simple method was compared with that calculated with a more detailed model, for different days in May, June and July in California, on almond (Prunus dulcis) and walnut (Juglans regia) trees. Daily net photosynthesis of 50 individual leaves was calculated as the daylight integral of the instantaneous photosynthesis. The latter was estimated for each leaf from its photosynthetic response to PAR and from the PAR incident on the leaf during the day. d Key Results Daily photosynthesis of individual leaves of both species was linearly related to the daily PAR incident on the leaves (which implies constant PhRUE throughout the canopy), but the slope (i.e. the PhRUE) differed between the species, over the growing season due to changes in photosynthetic properties of the leaves, and with differences in daily incident PAR. When PhRUE was estimated from the photosynthetic light response curve of a leaf at the top of the canopy and from the incident radiation above the canopy, obtained from weather-station data, the values were within 5 % of those calculated with the more detailed model, except in ®ve out of 34 cases. d Conclusions The simple method of estimating PhRUE is valuable as it simpli®es calculation of canopy photosynthesis to a multiplication between the PAR intercepted by the canopy, which can be obtained with remote sensing, and the PhRUE calculated from incident PAR, obtained from standard weather-station data, and from the photosynthetic properties of leaves at the top of the canopy. The latter properties are the sole crop parameters needed. While being simple, this method describes the differences in PhRUE related to crop, season, nutrient status and daily incident PAR.
HAL (Le Centre pour la Communication Scientifique Directe), Jun 19, 2011
Shoot structure, resulting from lateral branching and flowering patterns, determines final tree f... more Shoot structure, resulting from lateral branching and flowering patterns, determines final tree form, fruit bearing habit, and cropping potential. The genetic make-up of different cultivars controls vegetative and reproductive growth, but few structural studies have been done to systematically describe almond shoot structure. A specific class of Markovian models, referred to as hidden semi-Markov chains (HSMC), has been proposed to identify and characterize branching and flowering patterns in fruit trees. This type of model is particularly appropriate when the shoot structure is organized as a succession of homogeneous branching zones and captures the variable character of the observed patterns. This study reports the first almond HSMC analysis of shoot structure based on data collected from epicormic shoots and five length categories of proleptic shoots in three almond cultivars with distinctly different tree architecture. 'Nonpareil' is the most important cultivar grown in California and has a relatively spreading tree habit. 'Aldrich' is a newer cultivar with an upright growth habit, and 'Winters' has a spreading habit with a high tendency for sylleptic branching on proleptic shoots. Shoots of these three cultivars were analyzed to determine different zones that could be classified according to lateral bud fates and the number of flower buds at each node. This modeling technique showed that almond shoot structures are highly organized and predictable. Substantial differences were found in the structure of the proleptic shoots of similar length, among the cultivars, but fewer differences were found among epicormic shoots. For long shoots, 'Aldrich' had the highest probability of flower buds and 'Winters' had the greatest lateral branching distributed along shoots. 'Nonpareil' had similar branching probabilities as 'Aldrich' and its probability of flower buds was similar to 'Winters'. It is anticipated that these HSMC will be useful for identifying desirable shoot structures for cultivar improvement and will help to explain the differences in tree architecture and cropping potential among cultivars.
Reports that "own rooted" Chandler walnuts (Chandler clone) out preformed grafted trees stimulate... more Reports that "own rooted" Chandler walnuts (Chandler clone) out preformed grafted trees stimulated the creation of this replicated trial to investigate the performance of Chandler clone trees, Chandler clone grafted to Chandler clone rootstock, Chandler clone grafted to three selections of paradox rootstock and Chandler clone grafted to a vigorous English rootstock. Rootstock trees were planted in March 1999 at the California State University Farm in Chico. Tops were grafted with graft wood collected from mature Chandler clone trees in the spring of 2000. Initial survival, yield and trunk cross sectional area (TCSA) data collection began in 2001. Catkin abundance, tree yield, yield efficiency, and TCSA data was collected in 2004 and reported.
In this 18 year-old Chandler Orchard, where mechanical hedging has been the only method of prunin... more In this 18 year-old Chandler Orchard, where mechanical hedging has been the only method of pruning for the past 11 years, there was a significant yield differences between some treatments in 2003. A significant difference in accumulative yield was also observed between some of the five different hedging programs and the non-pruned trees. All treatments yielded between 2.9 and 4.1 tons per acre in 2003. A trial was begun in 1992 in a 6 year-old Chandler walnut orchard (26' x 26' spacing) comparing three hedging and two hand-pruning techniques. Four years of evaluations were made on economics, yield and fruit quality in this trial. The treatments for this first trial were:
Orchards that are planted in a hedgerow configuration eventually require some type of canopy mana... more Orchards that are planted in a hedgerow configuration eventually require some type of canopy management to allow safe machinery access down the drive row. The orchard age when this occurs varies depending on tree spacing, variety, orchard vigor, rootstock, etc. The Howard on Paradox orchard described here is the same orchard where a pruned versus unpruned trial took place from 2003 to 2010 (see Lampinen et.al, 2010). By 2010 the yields for all pruned and unpruned treatments were similar, as was midday canopy light interception, so the current trial was overlaid over the previous trial with individual rows serving as the treatment unit. OBJECTIVES The objective of the current study was to test different methods of managing a mature hedgerow Howard planting. The goal was to provide safe access for machinery down the drive row with minimal impacts on yield and or quality. An unhedged control was left to provide a reference to how much yield impact was occurring as a result of the mecha...
Reports that “own rooted” ‘Chandler’ walnuts out performed grafted trees stimulated the creation ... more Reports that “own rooted” ‘Chandler’ walnuts out performed grafted trees stimulated the creation of this replicated trial. The performance of own rooted ‘Chandler’ trees, ‘Chandler’ grafted to own rooted ‘Chandler’, and ‘Chandler’ grafted to three paradox selections and to a vigorous English selection is investigated in this trial. Rootstock trees were planted in March 1999 at the California State University Farm in Chico. Scions were grafted using wood collected from mature ‘Chandler’ trees in the spring of 2000. Initial survival, yield and trunk cross sectional area (TCSA) data collection began in 2001. Yield, nut quality, trunk circumference, and crown gall severity data was collected in 2008 and is reported here. OBJECTIVES The objectives of this trial are to investigate the following questions: a) Does a graft union have a limiting effect on tree growth and productivity? b) Is ‘Chandler’ a superior English rootstock? c) Do trees on clonal paradox show less variation than those ...
Reports that “own rooted” Chandler walnuts (Chandler clone) out preformed grafted trees stimulate... more Reports that “own rooted” Chandler walnuts (Chandler clone) out preformed grafted trees stimulated the creation of this replicated trial to investigate the performance of Chandler clone trees, Chandler clone grafted to Chandler clone rootstock, Chandler clone grafted to three selections of paradox rootstock and Chandler clone grafted to a vigorous English rootstock. Rootstock trees were planted in March 1999 at the California State University Farm in Chico. Tops were grafted with graft wood collected from mature Chandler clone trees in the spring of 2000. Initial survival, yield and trunk cross sectional area (TCSA) data collection began in 2001. Catkin abundance, tree yield, yield efficiency, and TCSA data was collected in 2004 and reported. OBJECTIVES The objectives of this trial are to validate or refute the following hypothesis: 1. Graft union has a limiting effect on tree growth and productivity. 2. Chandler is a superior English rootstock. 3. Clonal paradox has less variation ...
Journal of the American Society for Horticultural Science, 2013
Different almond (Prunus dulcis) cultivars have been characterized by their contrasting shoot bra... more Different almond (Prunus dulcis) cultivars have been characterized by their contrasting shoot branching patterns; however, the differences between patterns have been difficult to quantify. This study aimed to model the branching patterns of 2-year-old proleptic shoots on three almond cultivars (Nonpareil, Aldrich, and Winters) representing different tree architectures. The effects of branching pattern on flowering were also studied. The branching patterns of shoots of different length categories were assessed by a single hidden semi-Markov model for each cultivar. The models identified zones of homogeneous branching composition along shoots and were used to extract the occurrence and number of nodes of the zones according to shoot length categories. The numbers of flower buds were also determined for each shoot length category in each cultivar. The models of branching patterns of ‘Nonpareil’ and ‘Aldrich’ were similar and differed from the ‘Winters’ model. ‘Winters’ shoots produced ...
Background and Aims Photosynthetic radiation use ef®ciency (PhRUE) over the course of a day has b... more Background and Aims Photosynthetic radiation use ef®ciency (PhRUE) over the course of a day has been shown to be constant for leaves throughout a general canopy where nitrogen content (and thus photosynthetic properties) of leaves is distributed in relation to the light gradient. It has been suggested that this daily PhRUE can be calculated simply from the photosynthetic properties of a leaf at the top of the canopy and from the PAR incident on the canopy, which can be obtained from weather-station data. The objective of this study was to investigate whether this simple method allows estimation of PhRUE of different crops and with different daily incident PAR, and also during the growing season. d Methods The PhRUE calculated with this simple method was compared with that calculated with a more detailed model, for different days in May, June and July in California, on almond (Prunus dulcis) and walnut (Juglans regia) trees. Daily net photosynthesis of 50 individual leaves was calculated as the daylight integral of the instantaneous photosynthesis. The latter was estimated for each leaf from its photosynthetic response to PAR and from the PAR incident on the leaf during the day. d Key Results Daily photosynthesis of individual leaves of both species was linearly related to the daily PAR incident on the leaves (which implies constant PhRUE throughout the canopy), but the slope (i.e. the PhRUE) differed between the species, over the growing season due to changes in photosynthetic properties of the leaves, and with differences in daily incident PAR. When PhRUE was estimated from the photosynthetic light response curve of a leaf at the top of the canopy and from the incident radiation above the canopy, obtained from weather-station data, the values were within 5 % of those calculated with the more detailed model, except in ®ve out of 34 cases. d Conclusions The simple method of estimating PhRUE is valuable as it simpli®es calculation of canopy photosynthesis to a multiplication between the PAR intercepted by the canopy, which can be obtained with remote sensing, and the PhRUE calculated from incident PAR, obtained from standard weather-station data, and from the photosynthetic properties of leaves at the top of the canopy. The latter properties are the sole crop parameters needed. While being simple, this method describes the differences in PhRUE related to crop, season, nutrient status and daily incident PAR.
Proleptic shoots have different vegetative and reproductive characteristics that can be affected ... more Proleptic shoots have different vegetative and reproductive characteristics that can be affected by water availability; however the potential effects on shoot structure have been difficult to quantify. The aim of this study was to investigate how plant water status affects the structure or patterns of axillary meristem fates and flowering along proleptic shoots of almond trees. Hidden semi-Markov models were built for shoots growing on trees under two irrigation rate treatments. The shoot structures in each treatment were modeled with 7-state models corresponding to seven distinctive zones along the shoots. The transition probabilities between zones as well as the probability of axillary meristem fates and of the number of flower buds per node were not affected by irrigation treatments. Only one intermediate zone (fourth zone) along the shoots developed fewer nodes with the low irrigation rate. The central zones of shoots appear to be the most affected by factors such as mild water stress that reduce the growth or vigour of shoots.
Chandler' is the leading English walnut cultivar currently being planted in California. Rootstock... more Chandler' is the leading English walnut cultivar currently being planted in California. Rootstock selection can have significant effects on the performance of the scion in terms of catkin abundance, tree growth, yield efficiency, and the nut quality attributes of percent edible kernel and kernel color. This rootstock trial was planted in March 1999 in a randomized complete block design with six replicates of two trees per treatment at the California State University Farm in Chico. Six treatments are evaluated; three on English walnut roots and three on paradox walnut roots. Rootstock treatments include: own rooted 'Chandler', grafted and not grafted, English 'Waterloo', common paradox, 'Trinta' paradox, and 'Px1' clonal paradox. Own rooted trees have lower catkin abundance and yield efficiency but good nut quality and value. English walnut rootstocks are performing similarly to one another. 'Px1' paradox is similar to common paradox in nearly all respects and both stocks produce larger tree size than the 'Trinta' paradox rootstock. Own rooted 'Chandler' trees could provide an advantage in areas with a high incidence of blackline caused by cherry leaf roll virus since without a Northern California black or paradox rootstock English walnut trees can tolerate the disease.
Shoot structure, resulting from lateral branching and flowering patterns, determines final tree f... more Shoot structure, resulting from lateral branching and flowering patterns, determines final tree form, fruit bearing habit, and cropping potential. The genetic make-up of different cultivars controls vegetative and reproductive growth, but few structural studies have been done to systematically describe almond shoot structure. A specific class of Markovian models, referred to as hidden semi-Markov chains (HSMC), has been proposed to identify and characterize branching and flowering patterns in fruit trees. This type of model is particularly appropriate when the shoot structure is organized as a succession of homogeneous branching zones and captures the variable character of the observed patterns. This study reports the first almond HSMC analysis of shoot structure based on data collected from epicormic shoots and five length categories of proleptic shoots in three almond cultivars with distinctly different tree architecture. 'Nonpareil' is the most important cultivar grown in California and has a relatively spreading tree habit. 'Aldrich' is a newer cultivar with an upright growth habit, and 'Winters' has a spreading habit with a high tendency for sylleptic branching on proleptic shoots. Shoots of these three cultivars were analyzed to determine different zones that could be classified according to lateral bud fates and the number of flower buds at each node. This modeling technique showed that almond shoot structures are highly organized and predictable. Substantial differences were found in the structure of the proleptic shoots of similar length, among the cultivars, but fewer differences were found among epicormic shoots. For long shoots, 'Aldrich' had the highest probability of flower buds and 'Winters' had the greatest lateral branching distributed along shoots. 'Nonpareil' had similar branching probabilities as 'Aldrich' and its probability of flower buds was similar to 'Winters'. It is anticipated that these HSMC will be useful for identifying desirable shoot structures for cultivar improvement and will help to explain the differences in tree architecture and cropping potential among cultivars.
There are differences in walnut quality through the tree canopy which may be related to water rel... more There are differences in walnut quality through the tree canopy which may be related to water relations and/or light gradients. We have made significant progress on understanding the role of canopy position and light exposure on quality related problems in walnut. The data we have at present suggests that photosynthate reduction early in the season results in shriveled nuts while later restriction results in either yellow or black pellicles, depending on the timing. Some of the yellow nuts occurred in positions where the spur was in a well lit position early in the season but became shaded as the season progressed due to higher limbs coming down on top of them. All of the nuts with yellow and black pellicles had a mushy, wet hull surrounding the nut. The photosynthate reduction can be caused by low light conditions and/or loss of leaves. In addition, it appears that orchards running near the fully watered baseline (in the-4 to-5.5 bar midday stem water potential range) have a decrease in nut quality compared to orchards in the-6 to-7 bar range although the mechanism is not yet known.
Shoot characteristics differ depending on the meristem tissue that they originate from and enviro... more Shoot characteristics differ depending on the meristem tissue that they originate from and environmental conditions during their development. This study focused on the effects of plant water status on axillary meristem fate and flowering patterns along proleptic and epicormic shoots, as well as on shoot growth rates on 'Nonpareil' almond trees (Prunus dulcis). The aims were (1) to characterize the structural differences between proleptic and epicormic shoots, (2) to determine whether water deficits modify shoot structures differently depending on shoot type, and (3) to determine whether shoot structures are related to shoot growth rates. A hidden semi-Markov model of the axillary meristem fate and number of flower buds per node was built for two shoot types growing on trees exposed to three plant water status treatments. The models segmented observed shoots into successive homogeneous zones, which were compared between treatments. Shoot growth rates were calculated from shoo...
Abstract. A knowledge of spatio-temporal variability in potential yield is essential for site-spe... more Abstract. A knowledge of spatio-temporal variability in potential yield is essential for site-specific nutrient management in crop production. The objectives of this project were to develop a model for photosynthetically active radiation (PAR) intercepted by almond and walnut trees based on data obtained from respective tree(s) and estimate potential crop yield in individual trees or in blocks of five trees. This project uses proximally sensed PAR interception data measured using a lightbar mounted on a mobile platform and a crop growth model to estimate potential yields of almond and walnut trees. An analytical model was developed to estimate PAR intercepted by the tree in which tree canopy was assumed to be spherical in shape. PAR intercepted by a tree was estimated taking into account the effect of row spacing, tree spacing within the row, latitude and longitude of the orchard, day of the year and row orientation. Scans were collected at solar noon in almond and walnut orchards during the 2012 and 2013 growing seasons. Moreover, diurnal scans were also collected during 2012. Actual yield from those trees with lower values of midday PAR interception was found to be closer to their respective potential yield than those trees with higher values of midday PAR interception. These results suggest that there is a potential to use spatially variable PAR interception data to implement site-specific input management and enhance production.
Background and Aims Photosynthetic radiation use ef®ciency (PhRUE) over the course of a day has b... more Background and Aims Photosynthetic radiation use ef®ciency (PhRUE) over the course of a day has been shown to be constant for leaves throughout a general canopy where nitrogen content (and thus photosynthetic properties) of leaves is distributed in relation to the light gradient. It has been suggested that this daily PhRUE can be calculated simply from the photosynthetic properties of a leaf at the top of the canopy and from the PAR incident on the canopy, which can be obtained from weather-station data. The objective of this study was to investigate whether this simple method allows estimation of PhRUE of different crops and with different daily incident PAR, and also during the growing season. d Methods The PhRUE calculated with this simple method was compared with that calculated with a more detailed model, for different days in May, June and July in California, on almond (Prunus dulcis) and walnut (Juglans regia) trees. Daily net photosynthesis of 50 individual leaves was calculated as the daylight integral of the instantaneous photosynthesis. The latter was estimated for each leaf from its photosynthetic response to PAR and from the PAR incident on the leaf during the day. d Key Results Daily photosynthesis of individual leaves of both species was linearly related to the daily PAR incident on the leaves (which implies constant PhRUE throughout the canopy), but the slope (i.e. the PhRUE) differed between the species, over the growing season due to changes in photosynthetic properties of the leaves, and with differences in daily incident PAR. When PhRUE was estimated from the photosynthetic light response curve of a leaf at the top of the canopy and from the incident radiation above the canopy, obtained from weather-station data, the values were within 5 % of those calculated with the more detailed model, except in ®ve out of 34 cases. d Conclusions The simple method of estimating PhRUE is valuable as it simpli®es calculation of canopy photosynthesis to a multiplication between the PAR intercepted by the canopy, which can be obtained with remote sensing, and the PhRUE calculated from incident PAR, obtained from standard weather-station data, and from the photosynthetic properties of leaves at the top of the canopy. The latter properties are the sole crop parameters needed. While being simple, this method describes the differences in PhRUE related to crop, season, nutrient status and daily incident PAR.
HAL (Le Centre pour la Communication Scientifique Directe), Jun 19, 2011
Shoot structure, resulting from lateral branching and flowering patterns, determines final tree f... more Shoot structure, resulting from lateral branching and flowering patterns, determines final tree form, fruit bearing habit, and cropping potential. The genetic make-up of different cultivars controls vegetative and reproductive growth, but few structural studies have been done to systematically describe almond shoot structure. A specific class of Markovian models, referred to as hidden semi-Markov chains (HSMC), has been proposed to identify and characterize branching and flowering patterns in fruit trees. This type of model is particularly appropriate when the shoot structure is organized as a succession of homogeneous branching zones and captures the variable character of the observed patterns. This study reports the first almond HSMC analysis of shoot structure based on data collected from epicormic shoots and five length categories of proleptic shoots in three almond cultivars with distinctly different tree architecture. 'Nonpareil' is the most important cultivar grown in California and has a relatively spreading tree habit. 'Aldrich' is a newer cultivar with an upright growth habit, and 'Winters' has a spreading habit with a high tendency for sylleptic branching on proleptic shoots. Shoots of these three cultivars were analyzed to determine different zones that could be classified according to lateral bud fates and the number of flower buds at each node. This modeling technique showed that almond shoot structures are highly organized and predictable. Substantial differences were found in the structure of the proleptic shoots of similar length, among the cultivars, but fewer differences were found among epicormic shoots. For long shoots, 'Aldrich' had the highest probability of flower buds and 'Winters' had the greatest lateral branching distributed along shoots. 'Nonpareil' had similar branching probabilities as 'Aldrich' and its probability of flower buds was similar to 'Winters'. It is anticipated that these HSMC will be useful for identifying desirable shoot structures for cultivar improvement and will help to explain the differences in tree architecture and cropping potential among cultivars.
Reports that "own rooted" Chandler walnuts (Chandler clone) out preformed grafted trees stimulate... more Reports that "own rooted" Chandler walnuts (Chandler clone) out preformed grafted trees stimulated the creation of this replicated trial to investigate the performance of Chandler clone trees, Chandler clone grafted to Chandler clone rootstock, Chandler clone grafted to three selections of paradox rootstock and Chandler clone grafted to a vigorous English rootstock. Rootstock trees were planted in March 1999 at the California State University Farm in Chico. Tops were grafted with graft wood collected from mature Chandler clone trees in the spring of 2000. Initial survival, yield and trunk cross sectional area (TCSA) data collection began in 2001. Catkin abundance, tree yield, yield efficiency, and TCSA data was collected in 2004 and reported.
In this 18 year-old Chandler Orchard, where mechanical hedging has been the only method of prunin... more In this 18 year-old Chandler Orchard, where mechanical hedging has been the only method of pruning for the past 11 years, there was a significant yield differences between some treatments in 2003. A significant difference in accumulative yield was also observed between some of the five different hedging programs and the non-pruned trees. All treatments yielded between 2.9 and 4.1 tons per acre in 2003. A trial was begun in 1992 in a 6 year-old Chandler walnut orchard (26' x 26' spacing) comparing three hedging and two hand-pruning techniques. Four years of evaluations were made on economics, yield and fruit quality in this trial. The treatments for this first trial were:
Orchards that are planted in a hedgerow configuration eventually require some type of canopy mana... more Orchards that are planted in a hedgerow configuration eventually require some type of canopy management to allow safe machinery access down the drive row. The orchard age when this occurs varies depending on tree spacing, variety, orchard vigor, rootstock, etc. The Howard on Paradox orchard described here is the same orchard where a pruned versus unpruned trial took place from 2003 to 2010 (see Lampinen et.al, 2010). By 2010 the yields for all pruned and unpruned treatments were similar, as was midday canopy light interception, so the current trial was overlaid over the previous trial with individual rows serving as the treatment unit. OBJECTIVES The objective of the current study was to test different methods of managing a mature hedgerow Howard planting. The goal was to provide safe access for machinery down the drive row with minimal impacts on yield and or quality. An unhedged control was left to provide a reference to how much yield impact was occurring as a result of the mecha...
Reports that “own rooted” ‘Chandler’ walnuts out performed grafted trees stimulated the creation ... more Reports that “own rooted” ‘Chandler’ walnuts out performed grafted trees stimulated the creation of this replicated trial. The performance of own rooted ‘Chandler’ trees, ‘Chandler’ grafted to own rooted ‘Chandler’, and ‘Chandler’ grafted to three paradox selections and to a vigorous English selection is investigated in this trial. Rootstock trees were planted in March 1999 at the California State University Farm in Chico. Scions were grafted using wood collected from mature ‘Chandler’ trees in the spring of 2000. Initial survival, yield and trunk cross sectional area (TCSA) data collection began in 2001. Yield, nut quality, trunk circumference, and crown gall severity data was collected in 2008 and is reported here. OBJECTIVES The objectives of this trial are to investigate the following questions: a) Does a graft union have a limiting effect on tree growth and productivity? b) Is ‘Chandler’ a superior English rootstock? c) Do trees on clonal paradox show less variation than those ...
Reports that “own rooted” Chandler walnuts (Chandler clone) out preformed grafted trees stimulate... more Reports that “own rooted” Chandler walnuts (Chandler clone) out preformed grafted trees stimulated the creation of this replicated trial to investigate the performance of Chandler clone trees, Chandler clone grafted to Chandler clone rootstock, Chandler clone grafted to three selections of paradox rootstock and Chandler clone grafted to a vigorous English rootstock. Rootstock trees were planted in March 1999 at the California State University Farm in Chico. Tops were grafted with graft wood collected from mature Chandler clone trees in the spring of 2000. Initial survival, yield and trunk cross sectional area (TCSA) data collection began in 2001. Catkin abundance, tree yield, yield efficiency, and TCSA data was collected in 2004 and reported. OBJECTIVES The objectives of this trial are to validate or refute the following hypothesis: 1. Graft union has a limiting effect on tree growth and productivity. 2. Chandler is a superior English rootstock. 3. Clonal paradox has less variation ...
Journal of the American Society for Horticultural Science, 2013
Different almond (Prunus dulcis) cultivars have been characterized by their contrasting shoot bra... more Different almond (Prunus dulcis) cultivars have been characterized by their contrasting shoot branching patterns; however, the differences between patterns have been difficult to quantify. This study aimed to model the branching patterns of 2-year-old proleptic shoots on three almond cultivars (Nonpareil, Aldrich, and Winters) representing different tree architectures. The effects of branching pattern on flowering were also studied. The branching patterns of shoots of different length categories were assessed by a single hidden semi-Markov model for each cultivar. The models identified zones of homogeneous branching composition along shoots and were used to extract the occurrence and number of nodes of the zones according to shoot length categories. The numbers of flower buds were also determined for each shoot length category in each cultivar. The models of branching patterns of ‘Nonpareil’ and ‘Aldrich’ were similar and differed from the ‘Winters’ model. ‘Winters’ shoots produced ...
Background and Aims Photosynthetic radiation use ef®ciency (PhRUE) over the course of a day has b... more Background and Aims Photosynthetic radiation use ef®ciency (PhRUE) over the course of a day has been shown to be constant for leaves throughout a general canopy where nitrogen content (and thus photosynthetic properties) of leaves is distributed in relation to the light gradient. It has been suggested that this daily PhRUE can be calculated simply from the photosynthetic properties of a leaf at the top of the canopy and from the PAR incident on the canopy, which can be obtained from weather-station data. The objective of this study was to investigate whether this simple method allows estimation of PhRUE of different crops and with different daily incident PAR, and also during the growing season. d Methods The PhRUE calculated with this simple method was compared with that calculated with a more detailed model, for different days in May, June and July in California, on almond (Prunus dulcis) and walnut (Juglans regia) trees. Daily net photosynthesis of 50 individual leaves was calculated as the daylight integral of the instantaneous photosynthesis. The latter was estimated for each leaf from its photosynthetic response to PAR and from the PAR incident on the leaf during the day. d Key Results Daily photosynthesis of individual leaves of both species was linearly related to the daily PAR incident on the leaves (which implies constant PhRUE throughout the canopy), but the slope (i.e. the PhRUE) differed between the species, over the growing season due to changes in photosynthetic properties of the leaves, and with differences in daily incident PAR. When PhRUE was estimated from the photosynthetic light response curve of a leaf at the top of the canopy and from the incident radiation above the canopy, obtained from weather-station data, the values were within 5 % of those calculated with the more detailed model, except in ®ve out of 34 cases. d Conclusions The simple method of estimating PhRUE is valuable as it simpli®es calculation of canopy photosynthesis to a multiplication between the PAR intercepted by the canopy, which can be obtained with remote sensing, and the PhRUE calculated from incident PAR, obtained from standard weather-station data, and from the photosynthetic properties of leaves at the top of the canopy. The latter properties are the sole crop parameters needed. While being simple, this method describes the differences in PhRUE related to crop, season, nutrient status and daily incident PAR.
Proleptic shoots have different vegetative and reproductive characteristics that can be affected ... more Proleptic shoots have different vegetative and reproductive characteristics that can be affected by water availability; however the potential effects on shoot structure have been difficult to quantify. The aim of this study was to investigate how plant water status affects the structure or patterns of axillary meristem fates and flowering along proleptic shoots of almond trees. Hidden semi-Markov models were built for shoots growing on trees under two irrigation rate treatments. The shoot structures in each treatment were modeled with 7-state models corresponding to seven distinctive zones along the shoots. The transition probabilities between zones as well as the probability of axillary meristem fates and of the number of flower buds per node were not affected by irrigation treatments. Only one intermediate zone (fourth zone) along the shoots developed fewer nodes with the low irrigation rate. The central zones of shoots appear to be the most affected by factors such as mild water stress that reduce the growth or vigour of shoots.
Chandler' is the leading English walnut cultivar currently being planted in California. Rootstock... more Chandler' is the leading English walnut cultivar currently being planted in California. Rootstock selection can have significant effects on the performance of the scion in terms of catkin abundance, tree growth, yield efficiency, and the nut quality attributes of percent edible kernel and kernel color. This rootstock trial was planted in March 1999 in a randomized complete block design with six replicates of two trees per treatment at the California State University Farm in Chico. Six treatments are evaluated; three on English walnut roots and three on paradox walnut roots. Rootstock treatments include: own rooted 'Chandler', grafted and not grafted, English 'Waterloo', common paradox, 'Trinta' paradox, and 'Px1' clonal paradox. Own rooted trees have lower catkin abundance and yield efficiency but good nut quality and value. English walnut rootstocks are performing similarly to one another. 'Px1' paradox is similar to common paradox in nearly all respects and both stocks produce larger tree size than the 'Trinta' paradox rootstock. Own rooted 'Chandler' trees could provide an advantage in areas with a high incidence of blackline caused by cherry leaf roll virus since without a Northern California black or paradox rootstock English walnut trees can tolerate the disease.
Shoot structure, resulting from lateral branching and flowering patterns, determines final tree f... more Shoot structure, resulting from lateral branching and flowering patterns, determines final tree form, fruit bearing habit, and cropping potential. The genetic make-up of different cultivars controls vegetative and reproductive growth, but few structural studies have been done to systematically describe almond shoot structure. A specific class of Markovian models, referred to as hidden semi-Markov chains (HSMC), has been proposed to identify and characterize branching and flowering patterns in fruit trees. This type of model is particularly appropriate when the shoot structure is organized as a succession of homogeneous branching zones and captures the variable character of the observed patterns. This study reports the first almond HSMC analysis of shoot structure based on data collected from epicormic shoots and five length categories of proleptic shoots in three almond cultivars with distinctly different tree architecture. 'Nonpareil' is the most important cultivar grown in California and has a relatively spreading tree habit. 'Aldrich' is a newer cultivar with an upright growth habit, and 'Winters' has a spreading habit with a high tendency for sylleptic branching on proleptic shoots. Shoots of these three cultivars were analyzed to determine different zones that could be classified according to lateral bud fates and the number of flower buds at each node. This modeling technique showed that almond shoot structures are highly organized and predictable. Substantial differences were found in the structure of the proleptic shoots of similar length, among the cultivars, but fewer differences were found among epicormic shoots. For long shoots, 'Aldrich' had the highest probability of flower buds and 'Winters' had the greatest lateral branching distributed along shoots. 'Nonpareil' had similar branching probabilities as 'Aldrich' and its probability of flower buds was similar to 'Winters'. It is anticipated that these HSMC will be useful for identifying desirable shoot structures for cultivar improvement and will help to explain the differences in tree architecture and cropping potential among cultivars.
There are differences in walnut quality through the tree canopy which may be related to water rel... more There are differences in walnut quality through the tree canopy which may be related to water relations and/or light gradients. We have made significant progress on understanding the role of canopy position and light exposure on quality related problems in walnut. The data we have at present suggests that photosynthate reduction early in the season results in shriveled nuts while later restriction results in either yellow or black pellicles, depending on the timing. Some of the yellow nuts occurred in positions where the spur was in a well lit position early in the season but became shaded as the season progressed due to higher limbs coming down on top of them. All of the nuts with yellow and black pellicles had a mushy, wet hull surrounding the nut. The photosynthate reduction can be caused by low light conditions and/or loss of leaves. In addition, it appears that orchards running near the fully watered baseline (in the-4 to-5.5 bar midday stem water potential range) have a decrease in nut quality compared to orchards in the-6 to-7 bar range although the mechanism is not yet known.
Shoot characteristics differ depending on the meristem tissue that they originate from and enviro... more Shoot characteristics differ depending on the meristem tissue that they originate from and environmental conditions during their development. This study focused on the effects of plant water status on axillary meristem fate and flowering patterns along proleptic and epicormic shoots, as well as on shoot growth rates on 'Nonpareil' almond trees (Prunus dulcis). The aims were (1) to characterize the structural differences between proleptic and epicormic shoots, (2) to determine whether water deficits modify shoot structures differently depending on shoot type, and (3) to determine whether shoot structures are related to shoot growth rates. A hidden semi-Markov model of the axillary meristem fate and number of flower buds per node was built for two shoot types growing on trees exposed to three plant water status treatments. The models segmented observed shoots into successive homogeneous zones, which were compared between treatments. Shoot growth rates were calculated from shoo...
Uploads
Papers by Samuel Metcalf