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... 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.
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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... 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:
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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... 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...
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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... 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 ...
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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... 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 ...
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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... 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 ...
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absen
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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... 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...
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ABSTRACT Almond spurs are known to be the primary bearing unit in almond tree and are subject to alternate bearing. Fruits are a strong sink in bearing spurs and can influence spur leaf growth. At the same time the percent of flowers that... more
ABSTRACT Almond spurs are known to be the primary bearing unit in almond tree and are subject to alternate bearing. Fruits are a strong sink in bearing spurs and can influence spur leaf growth. At the same time the percent of flowers that set fruit on a spur (spur relative fruit set) could be influenced by the competition among multiple flowers/fruits borne on the same spur as well as by limited leaf area on the same spur. The aim of the present work was to investigate the relationship between current-year spur leaf area and spur absolute and relative fruit set. Approximately 2400 spurs were tagged and followed over 6 years and data concerning spur leaf area, number of flowers per spur, and number of fruits per spur were collected. Spur leaf area was reduced in fruiting spurs in comparison with non-fruiting spurs according to the number of fruits borne by each spur. This phenomenon contributes to spur alternate bearing because spur flowering and survival in the next year are a function of the leaf area in the current year. Relative fruit set in almond appears to be negatively associated with current-year spur leaf area. Competition among fruits on the same spur did not appear to influence spur relative fruit set.
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Almond spurs are known to be the primary bearing unit in almond tree and are subject to alternate bearing. Fruits are a strong sink in bearing spurs and can influence spur leaf growth. At the same time the percent of flowers that set... more
Almond spurs are known to be the primary bearing unit in almond tree and are subject to alternate bearing. Fruits are a strong sink in bearing spurs and can influence spur leaf growth. At the same time the percent of flowers that set fruit on a spur (spur relative fruit set) could be influenced by the competition among multiple flowers/fruits borne on the same spur as well as by limited leaf area on the same spur. The aim of the present work was to investigate the relationship between current-year spur leaf area and spur absolute and relative fruit set. Approximately 2400 spurs were tagged and followed over 6 years and data concerning spur leaf area, number of flowers per spur, and number of fruits per spur were collected. Spur leaf area was reduced in fruiting spurs in comparison with non-fruiting spurs according to the number of fruits borne by each spur. This phenomenon contributes to spur alternate bearing because spur flowering and survival in the next year are a function of th...
Drought reduces photosynthesis in walnut (Juglans regia L.), but it is not known whether this is due mainly to the closure of stomata, or to possible effects on leaf biochemistry. In an attempt to answer this question we studied diurnal... more
Drought reduces photosynthesis in walnut (Juglans regia L.), but it is not known whether this is due mainly to the closure of stomata, or to possible effects on leaf biochemistry. In an attempt to answer this question we studied diurnal changes in the water status and gas exchange in droughted [50% crop evapotranspiration (ET c)] and fully irrigated (100% ET c) walnut trees, over 2 d. Stem water potential (s) ranged from –0.5 MPa in the morning to –1.2 MPa in the afternoon under drought, and from –0.1 MPa to –0.4 MPa under full watering. Net CO 2 assimilation (A max) ranged from 15 µmol CO 2 m –2 s –1 in the morning to 3 µmol CO 2 m –2 s –1 in the afternoon under drought, and from 25 µmol CO 2 m –2 s –1 in the morning to 10 µmol CO 2 mm –2 s –1 in the afternoon under full watering. At these times, stomatal conductance (g s) varied from 0.2 to 0.02 mol H 2 O m –2 s –1 and from 0.7 to 0.2 mol H 2 O m –2 s –1 , respectvely. Drought reduced the internal CO 2 concentration (C i) by about...
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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... 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...
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Kaolin applied as a suspension to plant canopies forms a film on leaves that increases reflection and reduces absorption of light. Photosynthesis of individual leaves is decreased while the photosynthesis of the whole canopy remains... more
Kaolin applied as a suspension to plant canopies forms a film on leaves that increases reflection and reduces absorption of light. Photosynthesis of individual leaves is decreased while the photosynthesis of the whole canopy remains unaffected or even increases. This may result from a better distribution of light within the canopy following kaolin application, but this explanation has not been tested. The objective of this work was to study the effects of kaolin application on light distribution and absorption within tree canopies and, ultimately, on canopy photosynthesis and radiation use efficiency. Photosynthetically active radiation (PAR) incident on individual leaves within the canopy of almond (Prunus dulcis) and walnut (Juglans regia) trees was measured before and after kaolin application in order to study PAR distribution within the canopy. The PAR incident on, and reflected and transmitted by, the canopy was measured on the same day for kaolin-sprayed and control trees in o...
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Kaolin applications have been used to mitigate the negative effects of water and heat stress on plant physiology and productivity with variable results, ranging from increased to decreased yields and photosynthetic rates. The mechanisms... more
Kaolin applications have been used to mitigate the negative effects of water and heat stress on plant physiology and productivity with variable results, ranging from increased to decreased yields and photosynthetic rates. The mechanisms of action of kaolin applications are not clear: although the increased albedo reduces leaf temperature and the consequent heat stress, it also reduces the light available for photosynthesis, possibly offsetting benefits of lower temperature. The objective of this study was to investigate which of these effects are prevalent and under which conditions. A 6% kaolin suspension was applied on well-irrigated and water-stressed walnut (Juglans regia) and almond (Prunus dulcis) trees. Water status (i.e. stem water potential, psi(s)), gas exchange (i.e. light-saturated CO2 assimilation rate, Amax; stomatal conductance, g(s)), leaf temperature (T(l)) and physiological relationships in treated and control trees were then measured and compared. In both species,...
Research Interests: Water, Carbon Dioxide, Photosynthesis, Plant Biology, Ecology, and 8 moreLight, Temperature, Juglans, Dehydration, Prunus, Annals, Kaolin, and Plant Leaves
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The study was conducted on the Chandler variety at two sites, one in San Joaquin County and one in Tehama County. In the third year of the study, it was again difficult to maintain target levels of midday stem water potential at both... more
The study was conducted on the Chandler variety at two sites, one in San Joaquin County and one in Tehama County. In the third year of the study, it was again difficult to maintain target levels of midday stem water potential at both sites. Part of the reason for this was the gradual ...