Natural Leaf Fall Research Articles

Selection of Cotton for Early Natural Leaf Fall

In connection with environmental violations of the environment, there is a need to create cotton varieties with weak foliage or early natural deciduousness, high yields, resistance to diseases and environmental stress factors.

Physiological impacts of early defoliation on the cold hardiness of grapevine (Vitis vinifera L.) 'Sultana'

Low winter temperatures are one of the limiting factors of grape production worldwide. This study was undertaken to inquire about the effects of postharvest early defoliation on the cold hardiness of grapevine. The grapevines samples, cv. Sultana, were defoliated at two stages (10 and 25 days after harvest), and then they were compared with natural leaf fall. Cane samples were collected in December 2017 and February 2018, and analyzed in terms of water content, soluble carbohydrate, and proline concentrations in both bud and cane tissues. The samples were then subjected to freezing treatments i. e. -8, -12, -15, -18, -21, and -24 °C for evaluating the levels of cold hardiness. Based on these results, early defoliation reduced proline and soluble carbohydrate concentrations but increased the water content compared to the control. Leaf removal also decreased abscisic acid concentration in the bud samples. Investigation of cold hardiness by electrolyte leakage and tetrazolium staining examinations showed that the defoliation decreased cold hardiness. Results demonstrated that leaf removal between the growing season and the beginning of the acclimation stage decreased the metabolite concentration in buds and canes and resulted to a reduction of cold hardiness.

Apple fruit set is influenced by altered floral bud density but not by reduced carbohydrate reserves

The extent to which carbohydrate reserves contribute to apple (Malus × domestica Borkh.) fruit set is unclear. On ‘Royal Gala’/‘M9’ trees, we used postharvest early defoliation (12 days after harvest) to alter carbohydrate reserve accumulation compared with natural leaf fall. Superimposed over this, late winter bud thinning using artificial spur extinction (ASE, 6 buds cm(-1) branch cross sectional area) to manipulate the number of developing sinks in spring was compared with unmodified trees. Reducing bud density using ASE did not affect the concentration of total non-structural or soluble carbohydrates in root or spur tissues sampled at intervals from dormancy to final fruit set. However, ASE increased within-bud fruit set compared with unmodified trees. Early defoliation did not affect fruit set compared with natural defoliation, but reduced concentrations of total non-structural carbohydrates in roots in winter by 44% (264 to 147 mg g(-1) dry weight) and concentrations of starch in spurs in winter by 60% (19 to 7.7 mg g(-1)). Between dormancy and 1 week before bloom (WBB), total non-structural carbohydrate concentration declined in roots of naturally defoliated trees by 31%, and in spurs of naturally and early defoliated trees by 37 and 46% (respectively). In trees defoliated early, concentrations of total non-structural carbohydrates increased from their minimum at 1WBB in spurs and 2 weeks after bloom (WAB) in roots. In naturally defoliated trees total non-structural carbohydrates did not increase in roots during the measurement period, but increased in spurs between 5 and 9 WAB. Lack of differences in fruit set among defoliation treatments despite differences in non-structural carbohydrate concentration in spurs and roots implied that at concentrations observed here, stored carbohydrates in these tissues had little role in fruit set. This was supported by observations that total non-structural carbohydrate concentration declined before full bloom, not during fruit set, and total non-structural carbohydrate concentration increased during the period 2 to 4 WAB, when limitations in carbohydrate resources are thought most likely to affect fruit set.

Relationship among Entomosporium severity, defoliation, and vegetative-reproductive variables in pear in Brazil

Abstract: The objective of this work was to evaluate the relationship among Entomosporium severity, defoliation, and vegetative-reproductive variables of three European pear cultivars in Southern Brazil. The Packham’s Triumph, Abate Fetel, and Williams pear cultivars were assessed regarding Entomosporium severity, defoliation, and natural leaf fall every two weeks, from the appearance of the first symptoms at the beginning of January until the end of April, during the 2012/2013 and 2013/2014 crop seasons. The vegetative and reproductive variables were evaluated in July, during the dormant period. Data on Entomosporium severity were integrated over time and converted into the area under the disease progress curve (AUDPC). The coefficient of determination (R2) of the linear regression of Entomosporium severity versus defoliation was significant for all studied cultivars and crop seasons. Defoliation in trees affected by Entomosporium was significantly higher than natural leaf fall in the control trees protected by fungicides. A negative correlation was observed among defoliation, branch fertility index, and plant height, indicating that the higher the defoliation, the lower the development of the vegetative and reproductive variables plant height and vigor. Entomosporium severity differed significantly among cultivars when the AUDPC was considered the differentiating epidemiological variable. The Abate Fetel and Williams pear cultivars are the most susceptible and resistant to Entomosporium, respectively.

Decomposition and release of nutrients from leaf litter in rubber plantations

<p>Establishment of cover crop has been a standard scientific agronomic intervention in rubber (<em>Hevea brasiliensis</em>) plantations. Natural leaf fall in rubber plantations is an unaccounted phenomenon which also improves the physicochemical properties and biological activities of soil. A comparison of the decomposition of leaf litter from different sources in soil and the release of utrients from them has been attempted in this study through a field experiment. Studies indicated that the degradation and release of nutrients to the soil pool was mainly decided by the leaf chemistry and degradability of the litter. Rubber litter had its own edge over other leguminous cover crop litter, in providing a sustained release of potassium, calcium and magnesium owing to its slow and steady mineralization rate compared to cover crops. Higher content of nutrients was recorded in degraded litter in comparison to fresh sources. Legume cover crops are capable of enhancing the bacterial and fungal populations in soil compared to nonleguminous crops in rubber plantations.</p>

English

Cowpea is (Vigna unguiculata [L.] Walp.) is multipurpose legume grown for its edible grain and leaves and may be used as green manure or animal feed. The shoot biomass or fodder production of cowpea nodulation and effectiveness are seldomly considered in screening and release studies, yet such information is important for the use of the crop. A field study was therefore conducted Bunda College, (14° 35 S’; 33° 50 E’, Lilongwe, Malawi in the 2012 to 2013 cropping season to evaluate the performance of eight elite cowpea lines originally from the International Institute of Tropical Agriculture (IITA), compared to two released varieties (Sudan 1 and IT82E-16) for fodder production, nodulation and grain yield and yield components in a randomized complete block design. The results showed there were significant differences (P<0.05) in grain yield (1.1 to 3.1 t ha-1), fodder (1.1 to 3.0 tha-1) plant height at flowering (25 to 67 cm), pods m-2 (55 to 224), seeds per pod (10-14), cumulative leaf fall (0.9 to 1.8 tha-1) and nodules per plant (9 to 21). There were no significant differences on % nodule effectiveness (mean 95%) and canopy width at flowering (mean 51 cm). The elite line IT98K-205-8 produced the highest grain yield of 3,085 kg/ha followed by the variety Sudan 1 with 3,065 kg/ha and then elite line IT98K-205-9, which produced 2,763 kg ha-1. The lowest yielding elite line was IT93K-693-2 which gave 1,092 kg ha-1 of grain. Cumulative leaf fall accounted 31 to 94% of total fodder dry matter. Sudan 1 also had the highest nodules per plant (22) followed by IT82E-16 and IT99K1060. Estimated fodder N content was 2.4% giving 24 to 72 kg ha-1 as potential N in fodder. Although these lines were not selected as dual purpose, the results show opportunity for selecting dual purpose lines through evaluating for biomass. The released variety Sudan 1 notably had high grain yield, number of nodules and pods per plant. Key words: Cowpea nodulation, biomass production, natural leaf fall.

Effects of shoot girdling and/or periodic leaf removal on inflorescence primordia initiation and development inVitis vinifera L. cv. Sauvignon Blanc

Background and Aims Inflorescence primordia (IP) development starts in the buds of leaf axils approximately 12 months before flowering. Primordia initiation progresses acropetally as the shoot develops, although little is known about the timing of initiation at different node positions up the developing shoot. Girdling and/or leaf removal treatments were used to investigate the timing of development and structure of grapevine inflorescences at different positions along the shoot. Methods and Results Individual shoots were either girdled at their base shortly after fruitset or left intact. Leaves were then removed from those shoots on four occasions from the time of girdling to natural leaf fall in the autumn. Dormant latent buds from treatment shoots (shoot node positions one to ten) were grown as single-node cuttings (SNCs) in a glasshouse, and the inflorescence number per SNC and their architecture were scored on developing shoots. Girdling fully leafed shoots increased the proportion of SNC basal inflorescences with an outer arm but had no effect on the number of inflorescences per SNC. Girdled shoots that had their leaves removed at 0 or 4 weeks post-fruitset had a decrease in inflorescence number per SNC and outer arm development from nodes six and eight, respectively. Conclusions Inflorescence initiation before node positions six and eight was complete by the time girdling and leaf removal treatments were applied, and initiation at nodes six and eight occurred at 0 and 4 weeks post-fruitset. The development of the apical IP and the outer arm of the basal IP appears to occur at the same time. Significance of the Study This study presents novel information regarding the timing of IP initiation at different positions along the developing shoot, including the initiation and development of the outer arm. Also, the formation of an outer arm is shown to be sensitive to girdling and/or leaf removal.

Response of Lukasovka pear trees to foliar zinc sprays

The aim of the study was to examine the efficiency of foliar zinc (Zn) application in pear culture. The experiment was carried out in 2005-2007 in a commercial orchard in central Poland, on 6-8 year-old cv. Lukasovka pear trees, grown on coarse-textured soil, moderately abundant in organic matter or available Zn and slightly acidic in reaction. The trees were sprayed with Zn as EDTA in three periods: (1) before bloom: at the stage of bud break, and green and white bud, at a rate of 80 g Zn ha -1 in each spray treatment; (2) after bloom: at petal fall, and 14 and 21 days after full bloom, at a rate of 50 g Zn ha-1 per spray or; (3) after harvest, 3-4 weeks before natural leaf fall, at a rate of 200 g Zn ha-1. Trees unsprayed with Zn served as the control. The results showed, that pre-bloom Zn sprays increased status of this micronutrient in flowers, and post-bloom Zn sprays – in leaves and fruits. However, foliar Zn sprays had no effect on tree vigor, set of flowers and fruitlets, yielding, mean fruit weight, fruit russeting, and content of organic acids and soluble solids in fruit flesh. It is concluded that foliar Zn sprays of pear trees with an optimal leaf Zn status (according to the current threshold values) are not successful in improving plant growth, yielding, and fruit quality.

The timing of leaf fall affects cold acclimation by interactions with air temperature through water and carbohydrate contents

Three parameters (i.e. the water content, soluble sugar content and minimal air temperature) can be used to predict the cold acclimation process of walnut trees. In order to test this assumption, two-year-old walnuts were defoliated at two different dates, i.e. mechanical defoliation in early October (early leaf fall, EF) or natural defoliation in early November (natural leaf fall, NF) and conditioned in either outdoor freeze-deprived or cold-deprived ( T min > 13 °C) greenhouses over winter. Even if early defoliation date could have affected short day signal perception (SDSP), water balance and carbohydrate metabolism were more altered. EF treatment, by stopping transpiration, significantly increased tree's water content and at warm temperature high root activity stopped normal winter dehydration. Starch content decreased in all treatments, but there was only a significant increase in soluble sugar content when water content had sufficiently decreased. Thus, depending on date of defoliation, cold-deprived trees were or were not able to acclimate to frost (minimal frost hardiness = −21.8 °C vs. −22.1 °C in controls (freeze-deprived) for NF and −13.7 °C vs. −25.3 °C in controls for EF). Different treatments showed the relationship between minimal water content observed during winter and maximal soluble sugars synthesized. Thus, the cold acclimation process appeared dependent on these physiological parameters (water and soluble sugar contents) through the interaction between air temperature and timing of leaf fall.

Rendimento de uva 'Niagara Rosada' submetida à redução de área foliar

O objetivo deste trabalho foi verificar o efeito da perda da área foliar da videira, no período compreendido entre a colheita e a queda natural das folhas, sobre o rendimento das safras futuras. Após colheita realizada em 15-12-2005, selecionaram-se plantas que apresentavam oito ramos de produção. Os tratamentos constituíram-se de plantas com duas intensidades de desfolhas artificiais (25% e 50%), em quatro datas distintas (30; 45; 60 e 75 dias após a colheita - DAC), plantas sem redução artificial da área foliar, com proteção química (controle) e plantas sem redução artificial da área foliar e sem proteção química (testemunha). Dois ciclos de produção foram avaliados: ciclo da poda seca de julho/2006 com colheita em dezembro/2006 e ciclo da poda verde de fevereiro/2007 com colheita em junho/2007. Analisaram-se o crescimento de ramos, o número de cachos por planta e o rendimento (kg/planta) para os dois ciclos. Análises de regressão foram realizadas para as diferentes intensidades de redução de área foliar. A intensidade de desfolha após a colheita reduz o rendimento dos ciclos de produção futuros, porém não influencia no crescimento de ramos e no número de cachos produzidos na safra subsequente à redução da área foliar. O rendimento da safra da poda seca é maior do que a da poda verde.

Vegetative and Reproductive Responses of Apple Trees to Zinc Fertilization under Conditions of Acid Coarse-Textured Soil

ABSTRACT The aim of this study was to examine response of apple (Malus domestica Borkh.) trees to zinc (Zn) fertilization under conditions of acid coarse-textured soil with low 1M hydrochloric acid (HCl)-soluble Zn level. The experiment was carried out during 2004-2005 at a commercial orchard in Central Poland on mature ‘Jonagold’ apple trees/M.26 EMLA, planted at a spacing of 4 × 2.5 m. The trees were sprayed with Zn: (i) prebloom, at the stage of silver tip, and tight cluster at a rate of 140 and 100 g ha− 1, respectively, (ii) postbloom, at the stage of petal fall, and 2 weeks later at a rate of 80 g ha− 1 in each spray treatment, and (iii) postharvest, 4–5 weeks before the natural leaf fall at a rate of 500 g ha− 1. Other trees were supplied with Zn to soil at a rate of 3 kg ha− 1. In all the studied treatments, Zn was used as ethylenediaminetetraacetic acid (EDTA). Trees unsupplied with Zn served as the control. Tree vigor, fruit set, yield and fruit quality at harvest (mean fruit weight, firmness, color, russeting, soluble solids concentration, and acidity) were not influenced by Zn fertilization. Postharvest Zn sprays slightly damaged leaf tissues but did not cause defoliation. Soil Zn application raised Zn concentrations in flowers, and leaves 28, 56, and 84 days after petal fall. Pre- and postbloom Zn sprays increased Zn status in flowers and leaves 28 days after flowering, respectively. The obtained results indicate that Zn fertilization of ‘Jonagold’ apple trees with Zn status in mid-summer leaves and flowers of 17 mg kg− 1 and 27 mg kg− 1, respectively, is not successful in improving vigor and tree yield.

DECOMPOSITION OF DIVERSE LITTER MIXTURES IN STREAMS

In view of growing interest in understanding how biodiversity affects ecosystem functioning, we investigated effects of riparian plant diversity on litter decomposition in forest streams. Leaf litter from 10 deciduous tree species was collected during natural leaf fall at two locations (Massif Central in France and Carpathians in Romania) and exposed in the field in litter bags. There were 35 species combinations, with species richness ranging 1-10. Nonadditive effects on the decomposition of mixed-species litter were minor, although a small synergistic effect was observed in the Massif Central stream where observed litter mass remaining was significantly lower overall than expected from data on single-species litter. In addition, variability in litter mass remaining decreased with litter diversity at both locations. Mean nitrogen concentration of single- and mixed-species litters (0.68-4.47% of litter ash-free dry mass) accounted for a large part of the variation in litter mass loss across species combinations. For a given species or mixture, litter mass loss was also consistently faster in the Massif Central than in the Carpathians, and the similarity in general stream characteristics, other than temperature, suggests that this effect was largely due to differences in thermal regimes. These results support the notion that decomposition of litter mixtures is primarily driven by litter quality and environmental factors, rather than by species richness per se. However, the observed consistent decrease in variability of decomposition rate with increasing plant species richness indicates that conservation of riparian tree diversity is important even when decomposition rates are not greatly influenced by litter mixing.

Effect of Boron Fertilization on Sweet Cherry Tree Yield and Fruit Quality

ABSTRACT The goal of the study was to examine response of sweet cherries (Prunus avium L.) to boron (B) fertilization. The experiment was conducted during 2003–2004 in Central Poland on mature ‘Buttner's Red’ sweet cherry trees planted on a sandy loam soil with low B availability. Trees were soil-or foliar-fertilized with B. Soil B application was made at a rate of 2 kg ha−1 at the bud-burst stage. Foliar B sprays were performed: (1) in the spring, at the stage of white bud, beginning of flowering, and petal fall and (2) in the fall, approximately four to five weeks before the natural leaf fall. In each of spring spray treatments, B was applied at a rate of 0.2 kg ha−1 and in the fall at a rate of 0.8 kg ha−1. Trees untreated with B served as a control. The results showed that B fertilization had no effect on vigor and yield of sweet cherry trees despite increased concentration of this microelement in flower and leaf tissues. Mean fruit weight, titratable acidity, and fruit sensitivity to cracking also were not influenced by B fertilization. Fruits of B-fertilized trees, regardless of the method of its application, had higher concentrations of soluble solids and anthocyanins than did control plants. It is concluded that under conditions of this experiment, B fertilization can be recommended in sweet cherry culture to improve fruit quality and their appearance.

‘Schattenmorelle’ Tart Cherry Response to Boron Fertilization

ABSTRACT The objective of the experiment was to examine the effects of soil and foliar applications of boron (B) on tart cherry (Prunus cerasus L.) tree vigor, yield, and fruit quality. The study was conducted during 2003–2004 on mature ‘Schattenmorelle’ tart cherry trees grown at a commercial orchard in central Poland on coarse-textured soil with low B content. Trees were supplied with B as foliar sprays or via soil application. Foliar B sprays were performed: (1) in the spring, at the white bud stage, when 5%–10% of flowers were at full bloom, and 5 d after petal fall, at a rate of 0.2 kg B ha−1 per each spray treatment; and (2) in the fall, approximately six weeks before the natural leaf fall, at a rate of 0.8 kg B ha−1. Soil B application was made at the bud-break stage at a rate of 2 kg ha−1. Trees untreated with B served as a control. Spring and fall B sprays increased flower B concentrations, but had no effect on summer leaf B status. Leaf B concentrations of trees with B supplied to the soil were higher than those of the control trees. However, soil B application had no influence on flower B level. Vigor and yield of tart cherry trees were not influenced by B fertilization. Also, mean fruit weight and titratable acidity of fruit did not differ among treatments. Fruit of trees with B supplied to the soil had higher soluble solids concentration (SSC) than those of the control plants. In conclusion, high yield of tart cherry can be obtained on soils with water-soluble B concentrations as low as 0.32 mg kg−1. It is also postulated that at low soil-B availability, under conditions of low-light intensity during fruit ripening, soil-B application increases SSC in tart cherry fruit.

Growth and Fruiting of Young `Concord' Grapevines in Relation to Reserve Nitrogen and Carbohydrates

One-year-old `Concord' grapevines (Vitis labruscana Bailey) were fertigated with 0, 5, 10, 15, or 20 mm nitrogen by using a modified Hoagland's solution for 8 weeks during active vine growth in summer. Half of the vines at each N concentration were sprayed with 3% foliar urea twice in late September while the rest served as controls. After natural leaf fall, all the vines were overwintered in a cold room (2 to 4 °C). Four vines from each treatment were destructively sampled before budbreak for reserve N and carbohydrate analysis. The remaining vines were supplied with either no N or sufficient N (10 mm N) from 2 weeks before bloom to 1 month after bloom. All the vines were destructively harvested at 1 month after bloom. Total amount of N in dormant vines increased with increasing N fertigation concentration. Total nonstructural carbohydrates (TNC) increased with increasing N fertigation concentration from 0 to 10 mm, and then leveled off with further rises in N supply. Foliar urea application increased total N but decreased TNC of dormant vines at each given N fertigation level. When no N was provided during the regrowth period, vine total leaf area, fruit yield, and total dry weight increased with increasing N supply from fertigation the previous year. Vines sprayed with foliar urea the previous fall produced a larger total leaf area, a higher yield, and a higher total vine dry weight at each given N fertigation concentration. Providing vines with sufficient N during the regrowth period significantly increased total leaf area, fruit yield, and vine total dry weight across the previous N fertigation concentrations, but vines sprayed with foliar urea still had a larger leaf area, a higher yield, and a higher total vine dry weight at each given N fertigation concentration. Therefore, we conclude that both vegetative growth and fruiting of young `Concord' vines are largely determined by reserve nitrogen, not by reserve carbohydrates, and that current-season N supply plays a very important role in sustaining vine growth and development, especially fruit growth.

Nitrogen Storage and Its Interaction with Carbohydrates of Young Almond Trees in Response to Nitrogen Supply

June-budded `Nonpareil/Nemaguard' almond (Prunus dulcis (Mill) D.A. Webb) trees were fertigated with one of five nitrogen (N) concentrations (0, 5, 10, 15, or 20 mm) in a modified Hoagland's solution from July to September. In October, the trees were sprayed twice with either water or 3% urea, then harvested after natural leaf fall and stored at 2°C. Trees were destructively sampled during winter storage to determine their concentrations of amino acids, protein, and non-structural carbohydrates (TNC). Increasing N supply either via N fertigation during the growing season or with foliar urea applications in the fall increased the concentrations of both free and total amino acids, whereas decreased their C/N ratios. Moreover, as the N supply increased, the proportion of nitrogen stored as free amino acids also increased. However, protein was still the main form of N used for storage. The predominant amino acid in both the free and total amino-acid pools was arginine. Arginin N accounted for an increasing proportion of the total N in both the free and total amino acids as the N supply was increased. However, the proportion of arginine N was higher in the free amino acids than in the total amino acids. A negative relationship was found between total amino acid and non-structural carbohydrate concentrations, suggesting that TNC is increasingly used for N assimilation as the supply of N increases. Urea applications decreased the concentrations of glucose, fructose, and sucrose, but had little influence on concentrations of sorbitol and starch. We conclude that protein is the primary form of storage N, and that arginine is the predominant amino acid. Furthermore, the synthesis of amino acids and proteins comes at the expense of non-structural carbohydrates.

Nitrogen storage and its interaction with carbohydrates of young apple trees in response to nitrogen supply.

Bench-grafted 'Fuji/M.26' apple (Malus domestica Borkh.) trees received a constant nitrogen (N) supply (10.7 mM) from bud break to the end of June, and were then fertigated with 0, 5, 10, 15 or 20 mM N in a modified Hoagland's solution for 2 months during the summer. In mid-October, half of the trees fertigated at each N concentration were sprayed twice with 3% urea, whereas the remaining trees served as controls. All trees were harvested after natural leaf fall and were stored at 2 degrees C. Five trees from each of the N treatment combinations were destructively sampled during dormancy to determine the composition of N and total nonstructural carbohydrates (TNC). As the N supply from fertigation increased, amounts of N in both free amino acids and proteins increased, whereas C/N ratios decreased. Foliar urea applications in the fall significantly increased amounts of N in both free amino acids and proteins, but decreased their C/N ratios. Arginine, the most abundant amino acid in both free amino acids and in proteins, accounted for an increasing proportion of N in free amino acids and proteins with increasing N supply from fertigation or foliar urea application. The ratio of protein N to free amino acid N decreased from about 27.1 to 3.2 as N supply from fertigation increased from 0 to 20 mM, and decreased further to 3.0 in response to foliar urea applications in the fall. Concentrations of glucose, fructose, sucrose and TNC decreased as the N supply from fertigation increased, whereas concentrations of sorbitol and starch remained relatively unchanged. Foliar urea applications decreased the concentration of each TNC component and the TNC concentration in each N fertigation treatment. A negative linear relationship was found between carbon in TNC and N in proteins and free amino acids. The sum of carbon in TNC, proteins and free amino acids remained constant in response to N supply from fertigation. However, foliar urea applications decreased the sum of carbon in proteins, free amino acids and TNC because about 21% of the decrease in TNC carbon was not recovered in free amino acids or proteins. Young apple trees store N and carbon dynamically in response to N supply. As N supply increases, an increasing proportion of N is found in the form of free amino acids, which have a low carbon cost, although proteins remain the main form of N storage. Furthermore, part of the carbon from TNC is incorporated into amino acids and proteins, decreasing the carbon stored as TNC and increasing the carbon stored as amino acids and proteins.

Soil and foliar nitrogen supply affects the composition of nitrogen and carbohydrates in young almond trees

SummaryJune-budded ‘Nonpareil/Nemaguard’ almond (Prunus dulcis (Mill) D. A. Webb) trees were fertigated with one of five nitrogen (N) concentrations (0, 5, 10, 15, or 20 mM) in a modified Hoagland’s solution from July to September. In October, the trees were sprayed twice with either water or 3% urea, then harvested after natural leaf fall and stored at 2°C. Trees were destructively sampled during winter storage to determine their concentrations of amino acids, protein, and non-structural carbohydrates (TNC). Increasing N supply either via N fertigation during the growing season or with foliar urea applications in the fall increased the concentrations of both free and total amino acids, but decreased their C/N ratios. Moreover, as the N supply increased, the proportion of nitrogen stored as free amino acids also increased. However, protein was still the main form of N used for storage. The predominant amino acid in both the free and the total amino-acid pools was arginine. Arginine N accounted for an increasing proportion of the total N in both the free and the total amino acids as the nitrogen supply was increased. However, the proportion of arginine N was higher in the free amino acids than in the total amino acids. A negative relationship was found between total amino acid and non-structural carbohydrate concentrations, suggesting that TNC is increasingly used for N assimilation as the supply of nitrogen increases. Urea applications decreased the concentrations of glucose, fructose, and sucrose, but had little influence on concentrations of sorbitol and starch. We conclude that protein is the primary form of storage N, and that arginine is the predominant amino acid. Furthermore, the synthesis of amino acids and proteins comes at the expense of non-structural carbohydrates.

Spring growth of almond nursery trees depends upon nitrogen from both plant reserves and spring fertilizer application

SummaryJune-budded ‘Nonpareil’/‘Nemaguard’ almond (Prunus dulcis (Mill) D. A. Webb) trees were fertigated with one of five nitrogen (N) concentrations (0, 5, 10, 15, or 20 mM) from July to September. The trees were sprayed with either water or 3% urea in October, then harvested bareroot after natural leaf fall, and stored at 2°C. One set of trees was destructively sampled for total N content; the remaining trees were transplanted into N-free media in the spring after cold storage. After budbreak, these trees were supplied for 70.d with either N-free Hoagland’s solution or Hoagland’s solution containing 15N-NH4NO3. Nitrogen concentrations in both stem and root tissues were positively correlated with the N-fertigation concentration. Fall foliar urea applications increased levels of stem and root N regardless of the N-fertigation concentration. During the first 70 d of spring growth, the trees utilized nitrogen from both their reserves and spring fertilizer applications. The amount of N reserves used for growth of new shoots and leaves was proportional to the total amount of reserves. Trees with low N reserves relied primarily on the spring fertilizer as their source of nitrogen. We conclude, therefore, that both reserve N and spring-applied N fertilizers are important for enhancing the regrowth of bareroot almond nursery trees during establishment after transplanting. Nitrogen fertilization in the spring can especially improve the performance of trees with low N reserves.

Farmer experience with tree fodder

Use of trees for drought feed on New Zealand farms has been practised sporadically for many years, after farmers found that tree prunings were useful as supplementary feed during summer droughts. The Ministry of Agriculture &amp; Forestry (MAF) Sustainable Farming Fund recently funded a farmer-led team to develop the concept of tree fodder use on livestock farms in the southern North Island. Livestock farmers in Hawke's Bay, Rangitikei and Wairarapa who are already using tree fodder were interviewed to generate practical guidelines from their experience. Additional experience from Otago has been included here. Farmers obtain tree fodder by pruning and pollarding soil conservation trees, and by coppicing or grazing livestock on fodder blocks, or by taking advantage of natural leaf fall from poplar trees. The most common practice was pruning willows and poplars originally planted for soil conservation, during summer using a chainsaw. Most farmers found tree fodder feeding a valuable practice and well worthwhile. Over a three-tofour week period, two farmers reported taking 1.5-2 hours per day to feed 1,000 sheep, or cutting five or six trees per day to feed approximately 1,000 ewes. Keywords: tree fodder; poplars; willows; coppicing; pruning.