Soil Nitrogen Application Research Articles

Nitrogen use efficiency of sugarcane in relation to its BNF potential and population of endophytic diazotrophs at different N levels

The nitrogen fixing bacterial endophytes Gluconacetobacter diazotrophicus and Herbaspirillum spp. have been proposed to benefit sugarcane (Saccaharum spp. hybrids) growth. Variable populations of these endophytes exist depending upon ontogenic and climatic variations as well. This study investigates the effect of variable chemical nitrogen application in soil on the population of endophytic diazotrophs, acetylene reduction ability of excised roots, plant N-nutrient use efficiency and probable interactions among different parameters in eight commercial sugarcane varieties of subtropical India. Recovery efficiency (RE), agronomic efficiency (AE), partial factor productivity (PFP) and physiologic efficiency (PE) indicators were used for accounting N-nutrient use efficiency. The population of G. diazotrophicus was more at N75 compared to N0 and N150, whereas Herbaspirillum population increased from N0 to N150. ARA was positively correlated with Gluconacetobacter population in rhizosphere and root, whereas it had poor correlation with Herbaspirillum population. Positive correlation of RE and AE with ARA of roots, Gluconacetobacter and Herbaspirillum populations in roots and stems indicate their positive contribution in total nitrogen uptake by the plant per kg of N applied. Average PFP was 808.9 at N75 compared to 408.7 at N150 indicating that N was utilized efficiently at low N input status in sugarcane. Strong positive correlations of AE75 (agronomic efficiency from 75 kg N ha−1 to 150 kg N ha−1) with N-uptake (r 2 = 0.615), cane yield (r 2 = 0.758) and PFP (r 2 = 0.758) and other parameters compared to AE (agronomic efficiency from 0 kg N ha−1 to 75 kg N ha−1 or 150 kg N ha−1) correlations with N-uptake (r 2 = 0.111), cane yield (r 2 = 0.368) and PFP (r 2 = 0.190) indicated that the AE of sugarcane was strongly directed towards producing more cane yield per unit of N fertilizer once the sugarcane plant has established using initial dose of nitrogen and thus AE75 seems to be a more appropriate indicator for accounting N-nutrient use efficiency in sugarcane.

Influence of nitrogen on leaf chlorophyll content and photosynthesis of ‘Golden Delicious’ apple

The aim of the present study was to estimate the influence of different rates of soil-applied nitrogen on leaf N and chlorophyll content and photosynthesis in ‘Golden Delicious’ apple trees. Three different treatments were included: the trees were either fertilized with 80 kg N ha−1 (N-80), 250 kg N ha−1 (N-250) or left unfertilized (CON). Fertilization increased leaf nitrogen content, with a more prominent effect in high N application level treatment. In all treatments, a slight seasonal decrease in leaf nitrogen content was observed. N-250 treatment resulted in higher chlorophyll content; a similar effect was found late in the season for N-80 treatment. Measurements of A-C i curves, performed on spur leaves, revealed a higher CO2 saturated photosynthetic rate in N-250 trees compared with low application level fertilized or unfertilized trees. No effect of N fertilization on carboxylation efficiency was found, as revealed by comparisons of the initial slopes of A-C i curves. The lack of positive effect is rather surprising, since the leaf N content was efficiently increased with application of fertilizer. Obviously, the existing pool of leaf nitrogen in non-fertilized trees does not limit Rubisco activity and efficiency.

The effects of rate and timing of N fertilizer on growth, photosynthesis, N accumulation and yield of mustard ( Brassica juncea) subjected to defoliation

Mustard ( Brassica juncea L.) is characterized by large number of broad oblong shaped leaves in the lower layers. Our earlier studies have shown that removal of these shaded lower leaves on mustard plant axis enhanced growth, photosynthetic capacity and yield of the crop. We now present evidence that soil-applied nitrogen (N) at pre- or post-flowering stage following defoliation of lower leaves influences plant growth, photosynthesis and assimilation balance. Following defoliation at pre-flowering, i.e. 40 d after sowing (DAS) and N applied at the rate of 100 kg ha −1 at the time of sowing and 50 kg ha −1 at post-flowering (60 DAS) enhanced the characteristics maximally. The defoliation treatment together with N combinations and the time of its application, N at 150 kg ha −1 applied as single dose at the time of sowing or N applied in split; 100 kg ha −1 at the time of sowing and 50 kg ha −1 at 40 DAS or 75 kg ha −1 at the time of sowing or 75 kg ha −1 at pre- or post-flowering time proved less effective. The plants which were not defoliated and received 75 kg N ha −1 at the time of sowing and 75 kg ha −1 at 60 DAS showed lowest values. Furthermore, N assimilation was more efficient in plants following defoliation at 40 DAS. The results suggest that split N application (100 kg ha −1 at sowing and 50 kg ha −1 at post-flowering) enhances substantially growth, photosynthesis, N assimilation and yield of mustard following defoliation. This management practice could be adopted in mustard culture for increasing seed yield together with minimizing N loss.

Effect of Postharvest Sprays of Boron and Urea on Yield and Fruit Quality of Apple Trees

ABSTRACT The objective of the experiment was to examine the effect of postharvest sprays of boron (B) and urea on apple tree yield and fruit quality. The study was conducted during 2002–2003 at a commercial orchard in central Poland on mature ‘Jonagold’ apple trees/M.26 planted on a sandy loam soil with low B status. All experimental trees received soil-applied nitrogen (N) at a rate of 50 kg ha−1 at bud break. The following spray treatments were performed: (1) postharvest B spray three to four weeks before leaf abscission at a rate of 1.2 kg ha−1; (2) postharvest urea-N spray at the same time as B spraying at a rate of 18.4 kg ha−1; and (3) combined B spray with urea at the same time and at the same rates as in the combination of treatments (1) and (2). Trees not sprayed with B and urea served as a control. The results showed that all spray treatments damaged leaves, but only postharvest urea spray and combined B spray with urea caused defoliation. Postharvest B spray with/without urea improved flower B status, fruit set, and tree yield. However, the efficiency of combined B spray with urea in improving reproductive growth was lower than that of foliar B application without the addition of urea. Postharvest sprays of B and urea had no effect o n blushing, flesh firmness, or soluble solids concentration of apple fruit. These results indicated that under B-deficiency conditions, postharvest B sprays are successful in improving reproductive growth and should be recommended without the addition of urea. It is suggested that combined B sprays with urea may be applied in the autumn to apple trees with limited soil B and N availability.

Growth and yield responses of apricot (cv. Moorpark) to soil-applied nitrogen

The effect of soil-applied nitrogen on the growth and yield of 12-year-old apricot Prunus armeniaca cultivar Moorpark trees growing on an orthic Tenosol in the Riverland region of South Australia was studied over 3 years. The experiment was set up in a randomised complete block design with 6 annual rates of nitrogen (0, 250, 500, 750, 1000 and 1250 g/tree.year) applied in the form of ammonium nitrate. Application was split into 30% at budburst, 30% 6 weeks after budburst and 40% after harvest. Growth in trunk circumference was significantly greater at 750 and 1000 g/tree.year than at the other rates of nitrogen. In years 1 and 2, the weight of water shoot growth removed at pruning was significantly higher at nitrogen rates of 750–1250 g/tree.year than from trees that received no nitrogen. It is suggested that for Moorpark apricots growing on an orthic Tenosol, applying nitrogen at rates of 750 g/tree.year and above produces levels of water shoot growth that are undesirable for tree management. Nitrogen application resulted in darker and more vivid green leaves as measured with a Minolta Chroma Meter. Concentration of nitrogen in mid-shoot leaves was increased with increase in applied nitrogen. Fruit size was significantly increased by applied nitrogen in year 1, but fruit size was not significantly affected in years 2 and 3. Nitrogen application increased fruit set in the second and third year. Yield of fresh fruit was not significantly affected in the first year, but was in subsequent years with the maximum yield obtained at a rate of 1000 g/tree.year of nitrogen in both years. Yield of dried fruit followed similar trends to that of fresh fruit. Fruit maturation was delayed by 4 to 8 days by nitrogen application. After 3 years, applying nitrogen at 1250 g/tree.year the pH of soil in the top 15 cm was 4.7 compared with 6.7 where no nitrogen was applied.

Quality of fresh and dried fruit of apricot (cv. Moorpark) in response to soil-applied nitrogen

The effects of soil applications of nitrogen on the quality of fresh and dried fruit from 12-year-old apricot Prunus armeniaca cultivar Moorpark trees growing on an orthic Tenosol in the Riverland region of South Australia were studied over 3 years. The experiment was set up in a randomised complete block design with 6 annual rates of nitrogen (0, 250, 500, 750, 1000 and 1250 g/tree.year) applied in the form of ammonium nitrate. Application was split into 30% at budburst, 30% six weeks after budburst and 40% after harvest. Firmness of fruit was significantly reduced as the rate of applied nitrogen increased. The flesh of individual fruits ripened more evenly when 0 or 250 g nitrogen/tree.year was applied, compared with rates in the range 500–1250 g nitrogen/tree.year. Application of nitrogen significantly increased the pH of fruit. The total soluble solids level of fruit from trees that received 0 or 250 g nitrogen/tree.year, was significantly lower than from trees that received 750 or 1250, but not 1000 g nitrogen/tree.year. Application of nitrogen did not significantly affect the concentration of sulfur dioxide in fresh fruit measured after sulfuring, but the concentration of sulfur dioxide in fruit at the completion of drying was significantly increased. The application of nitrogen did not affect the drying ratio of fruit. Nitrogen application increased the rate of darkening of dried apricots in storage in each of the three years. Relationships were found between time taken for dried apricots to darken to an unacceptable level and nitrogen concentration in harvested fruit. It is suggested that to assist in the management of darkening of dried apricots in storage, annual nitrogen application rates on an orthic Tenosol need to be below 500 g/tree.year and ideally below 250 g/tree.year.

Environmental Losses of Soil-applied Nitrogen Sources in Lowbush Blueberry Production

Environmental losses of soil-applied nitrogen fertilizers were examined during 2004 in commercial wild blueberry fields in the vegetative phase of production in Nova Scotia (NS) and Prince Edward Island (PE). A randomized complete-block experimental design with five treatments, five replications, a plot size of 8 × 6 m, and 2-m buffers between plots was used. Treatments consisted of a control (no fertilizer application) and nitrogen applications (N at 35 kg·ha-1) of ammonium sulphate (AS), urea (U), diammonium phosphate (DAP), and sulfur-coated urea (SCU). Nitrogen applications occurred on 19 May and 9 June at the Kemptown (NS) and Mount Vernon (PE) sites, respectively. Cumulative ammonia volatilization was determined through the use of open top chambers with volatilization samples collected on 1, 2, 5, 8, and 12 days after treatment application. In addition, leaf tissue and yield component data were collected. A significant volatilization treatment effect was present at the Kemptown site with the U and SCU treatments having volatilization rates that were 321% and 207% greater than the control, respectively. Therefore, results from this study indicate that volatilization losses are significant and site specific and can negatively influence blueberry growth.

Ning reactions during storage of low-moisture Australian sultanas: Effects of vine nitrogen nutrition on subsequent arginine-mediated Maillard reactions during storage of dried fruit

Ten-year old Vitis Vinifera L. cv. Sultana (Thompson Seedless) grape vines were transferred into large cement pots in low nitrate soil and supplemented with four levels of nitrogen application in the form of ammonium nitrate as follows: 0 g (N0), 8.5 g (N1), 17.0 g (N2) and 25.0 g (N3). Grapes were harvested from each nitrogen treatment, dipped and dried to low moisture (˜11.4%) and subsequently stored for 10 months at 10oC and at 30oC in either the presence or absence of oxygen. The pre-storage concentration of free arginine, free-proline and total protein in the dried sultanas increased with soil nitrogen application. Skin-polyphenoloxidase (PPO) activity was higher in sultanas with added soil nitrogen (N1, N2, N3), however pre-storage differences in total phenolics, and the PPO substrate, trans-caftaric acid, were not significantly different. After 10 months storage at 30oC significant browning was observed in both the presence and absence of oxygen. Greater browning corresponded to higher soil-nitrogen application rates. The concentration of skin trans-caftaric acid did not decrease in N0, N1 or N2 after 10 months at 30oC, in either the presence or absence of oxygen, although some decreases were measured in the highest nitrogen sultanas (N3). While PPO oxidation of the phenolic substrate trans-caftaric acid was not the primary route to browning, a number of Maillard reaction products (MRP) were present in both sultanas and arginine-glucose model systems. Those products were separated via reverse phase HPLC and partially characterised by UV-diode array spectroscopy. The lack of oxidation of trans-caftaric acid observed in the nitrogen storage trial was confirmed in an accelerated browning experiment in low-moisture sultanas, where despite browning at 50oC after 12 days, no decreases in this primary substrate for PPO-mediated oxidation were measured.

Effects of spring soil nitrogen application on nitrogen remobilization, uptake, and partitioning for new growth in almond nursery plants

SummaryOne year old ‘Nonpareil’ almond (Prunus dulcis (Mill) D. A. Webb) trees on ‘Lovell’ rootstocks were used to evaluate the effects of soil nitrogen (N) availability in the spring on N remobilization, uptake, partitioning, and tree growth. After being transplanted to an N-free medium, the trees received a modified Hoagland solution, with or without N from 15N-depleted NH4NO3, twice a week for 12 weeks. During the first four weeks, the N used for new shoot and leaf growth mainly came from the nitrogen that had accumulated in storage tissues. No significant differences were seen in the amount and duration of N remobilization between N-fertilized trees and those that received no N. However, trees that were fertilized in the spring had significantly more new shoot and leaf growth. Uptake of 15N by the roots began two weeks after transplanting. Nitrogen was rapidly taken up from the soil during the period of greatest shoot and leaf growth; leaves were the major sink for N from both root uptake and storage. Six weeks after transplanting, the whole-tree N content was significantly higher in fertilized trees than in the controls. We conclude that the remobilization of N for spring new growth takes place irrespective of the current-year external N supply. However, the new growth in young almond trees is highly dependent on soil N availability, which demonstrates the importance of spring N fertilizer applications following transplantation.

Changes in Chemical Composition of Australian Waxflowers Due to Soil Applications of Nitrogen and Assessment of Nitrogen Status by Tissue Analysis

Three field experiments were conducted to investigate the effects of soil‐applied nitrogen (N) on plant chemical composition, nutrient removal, and the use of plant analysis to assess N status of Australian waxflowers. Experiments were conducted in commercial plantings of Chamelaucium uncinatum cultivar Alba and a Chamelaucium hybrid (C. floriferum × C. uncinatum) known locally as Walpole wax, at 3 sites in South Australia. Nitrogen, as ammonium nitrate, was applied at rates up to 160 g plant−1 over several side dressings during the growing season. To assess plant nutrient status, stem tips (25–40 mm long tips of stems) were sampled during the growing season and whole stems at harvest. Nitrogen concentration in both stem tips and whole stems was sensitive to variations in N supply; however, the magnitude of the effect varied between sampling times and sites. In stem tips sampled during spring, the increase in N concentrations ranged from 19.8% at site 2 to 74.6% at site 1. Nitrogen concentrations in stem tips were consistently greater than concentrations in whole stems. The application of N decreased phosphorus (P) concentrations in whole stems and copper (Cu) concentrations in stem tips and whole stems. There was no consistent effect of applied N on potassium (K), calcium (Ca), magnesium (Mg), boron (B), zinc (Zn), and manganese (Mn) concentrations in either plant part sampled. Nutrient removal by flowering stems, in order from greatest to least, was N > K > Ca > P > Mg > Mn > B > Zn > Cu. Based on 1800 plants ha−1, it was estimated that for N, P, and K, 121.9, 15.4, 60.1 kg ha−1, respectively, was removed in harvested stems. Based on poor sensitivity, the lack of a sharp transition zone between deficient and adequate N concentrations and the lack of consistent relationships between N concentration in stem tips and yield response, it is concluded that N concentration in stem tips is not a useful indicator of the N status of waxflower plants.

A method for livestock waste management planning in NE Spain

A method of decision-making on livestock wastes management in areas with nutrient surplus due to high livestock density is applied in Catalonia (NE Spain). Nutrient balance is made considering soil nitrogen application as the limiting factor. Special attention is paid to the centralized treatment option. The method presented consists of: 1. minimizing livestock waste generation (at farm scale) as a step previous to any other, both in amount and limiting components, 2. applying the nitrogen balance method at regional and municipal scale and providing enough storage capacity in order to apply wastes in an agronomically correct way, 3. spatially refining the results of the nitrogen balance by a proposed method that allows precisely pinpointing the hotspots of livestock waste generation, where centralized treatment might be an interesting option, and 4. deciding on the waste treatment objectives, provided that treatments be necessary. Knowledge about the wastes, meeting the interests and merging the efforts of the various actors, as well as an adequate budget are necessary ingredients for the success of any waste management plan.

Properly Timed Soil-applied Nitrogen Fertilizer Increases Yield and Fruit Size of `Hass' Avocado

To protect groundwater from potential nitrate pollution, `Hass' avocado (Persea americana Mill.) growers in California divide the total annual soil-applied nitrogen (N) fertilizer (N at 56 to 168 kg·ha-1) into small applications made during the period from late January to early November. However, no research had been conducted to test the efficacy of this fertilization practice, and there was concern that the amount of N in the individual applications may be too little to meet the demand of the tree at some stages of its phenology. The research presented herein addressed the question of whether yield of `Hass' avocado could be increased by doubling the amount of N currently applied during specific stages of tree phenology. The control in this experiment was the practice of annually applying N as NH4NO3 at 168 kg·ha-1 (168 trees/ha) in six small doses of N at 28 kg·ha-1 in January, February, April, June, July, and November. From these six application times, five were selected on the basis of tree phenology and additional N as NH4NO3 at 28 kg·ha-1 was applied at each time for total annual N of 196 kg·ha-1. Two phenological stages were identified for which N application at 56 kg·ha-1 in a single application (double dose of N) significantly increased the 4-year cumulative yield (kilograms fruit per tree) 30% and 39%, respectively, compared to control trees (P ≤ 0.01). In each case, more than 70% of the net increase in yield was commercially valuable large size fruit (178 to 325 g/fruit). The two phenological stages were when shoot apical buds have four or more secondary axis inflorescence meristems present (mid-November); and during anthesis to early fruit set and initiation of the vegetative shoot flush at the apex of indeterminate floral shoots (about mid-April). When the double dose of N was applied at either of these two stages, the kilograms and number of large size fruit averaged across the 4 years of the study was significantly greater than the control trees (P ≤ 0.01). Averaged across the 4 years of the study, only the November treatment increased yield compared to the control trees (P ≤ 0.05). Application of the double dose of N at flower initiation (January), during early-stage gynoecium development (February), or during June drop had no significant effect on average or cumulative yield or fruit size compared to control trees. Application of the double dose of N in April significantly reduced the severity of alternate bearing (P ≤ 0.05). Yield was not significantly correlated with leaf N concentration. Time and rate of N application are factors that can be optimized to increase yield, fruit size, and annual cropping of `Hass' avocado. When the amounts of N applied were equal (196 kg·ha-1), time of application was the more important factor.

Soil nitrogen application in the spring did not increase apple yield

Since there is no chemical method to assess N availability from field soil samples, this nutrient is still recommended based on regional field trials. This study aimed to evaluate the effect of spring application of N to the soil on fruit yield of apple cultivars. Two experiments were carried out, respectively for ‘Gala’ and ‘Fuji’. The trees, grafted on MM 106 rootstock, were planted in 1987, spaced 4.50 x 1.80m, in a clayed Oxisol (Hapludox) with 4.0% of organic matter, in Vacaria (RS), Southern Brazil. Treatments were applied annually, from the spring of 1990, in the tree row, over a 1.5-m-wide strip, as urea, and consisted of four rates of N corresponding to 0, 27.5, 55.0 and 82.5kg ha-1 in the first three years, and respectively 0, 50, 100 and 120kg ha-1 in the remaining two years. Data were collected for four years, starting at the 91/92 growing season. Application of increasing rates of N to the soil during five years had no effect on fruit yield and on concentration of N in the leaves regardless of year and cultivar. Average annual fruit yield varied from 50 to 70t ha-1 for ‘Gala’ and from 39 to 89t ha-1 for ‘Fuji’, but in the entire period the average yield was similar for both cultivars, approximately 56t ha-1. Concentration of N in the leaves was always in the normal range (2.0 to 2.5%) for ‘Fuji’, and slightly lower for ‘Gala’, but above 1.9%. Total N requirement for tree growth and fruiting, thus, came from soil organic matter decay.

Disease control and yield improvement obtained with fungicide applications to spring wheat in South Africa

Foliar sprays containing benzimidazole and/or compounds inhibiting ergosterol biosynthesis in fungi were tested for their effects on spring wheat at different localities in the Western Cape Province, South Africa. Fungicide treatments caused significant yield increases ( P > 0.05) at most of the localities where plants were sprayed at Zadok's growth stages 31 and 39. Plants were affected by physiological leaf spot, which occurred in all localities. At one locality good control of leaf rust ( Pucdnia recondita f.sp. tritici) was obtained with triazole-containing sprays, but not with imidazole- and benzimidazole-containing sprays. Lodging due to eyespot ( Tapesia yallundae) occurred at another locality where it was partially controlled by benzimidazole-containing fungicide mixtures. Fungicides had little or no effect on yield when planting date was delayed or when the rate of soil-applied nitrogen on fallow land was increased. The study indicates that in the Western Cape Province growth regulating effects, rather than fungicidal effects of fungicides, are often responsible for yield increases of wheat.

Rootstock, Time, Technique, and Quantity of Nitrogen Effects on Production, Mineral Nutrition, and Postharvest Quality of `Fuji' Apple

The influence of three rootstocks, various levels of soil-applied nitrogen in fall, and spring spray applications with and without minimum ground nitrogen on tree growth, productivity, leaf and fruit nutrient partitioning, and postharvest quality of fruit at harvest and after storage in `B.C. 2 Fuji' apple was studied over several seasons. Early results showed that trees on M.26 and M.9 were more precocious and had higher yield and yield efficiency. Trees on M.9 had significantly higher leaf Ca and incidence of sunburned fruit than those on other rootstocks. Trees on M.7 had larger fruit and higher leaf N, K, and Cu, but had lower fruit starch degradation pattern (SDP) and leaf Ca. Soluble solids at harvest were lower in fruit from trees on M.26 rootstock. Trees with fall nitrogen application had lower leaf N and better fruit color. Lower quantities of N application had smaller fruit but better fruit color and higher firmness at harvest. Fruit from all rootstocks did not produce ethylene for several days in the ripening chambers. After this period, fruit on M.9 rootstock produced ethylene before those from other rootstocks. Trees established with only nitrogen spray without any ground application had leaf N deficiency after they started bearing fruit. Establishment of a new `Fuji' orchard based on only nitrogen spray produced weak trees with low yield and yield efficiency, while addition of a small quantity of ground-applied N improved tree growth and fruit quality.

THE RESPONSE OF BRAMLEY'S SEEDLING APPLE TREES TO SOIL AND FOLIAR APPLIED NITROGEN

THE RESPONSE OF BRAMLEY'S SEEDLING APPLE TREES TO SOIL AND FOLIAR APPLIED NITROGEN

240 RELATIONSHIP OF GROWING LOCATIONS, HARVEST MATURITY, SUMMER PRUNING, SOIL NITROGEN APPLICATION, AND STORAGE ON FRUIT POSTHARVEST PERFORMANCE IN `HAYWARD' KIWIFRUIT

Fruit from 8 `Hayward' kiwifruit vineyards in central California were harvested at 2 week intervals after soluble solids content (SSC) reached 6% and subjected to 4 and 6 months of storage at 0°C in an ethylene free environment. Fruit characteristics at harvest and postharvest performance varied considerably among locations. Fruit stored for 6 months had the same fresh weight, less flesh firmness and higher SSC, than the 4 months storage. Later harvested fruit had greater fruit flesh firmness and higher SSC after storage. SSC after storage was predictable based on ripe soluble solids content (RSSC) at harvest. Summer pruning reduced while soil nitrogen application increased fruit SSC.

713 PB 391 RELATIONSHIP OF MACRO-MINERAL NUTRITION ON FRUIT POSTHARVEST PERFORMANCE IN `HAYWARD' KIWIFRUIT

Fruit from 8 `Hayward' kiwifruit vineyards in central California were harvested at 2 week intervals after soluble solids content (SSC) reached 6% and subjected to 4 and 6 months of storage at 0°C in an ethylene free environment. Macro-nutrients were analyzed from leaf and fruit tissues. Leaf petiole N and NO3--N were 2 to 3 times higher for vines that had softer fruit after long-term storage. Where the correlations were significant, fruit firmness and SSC were correlated negatively with N, P, K, Cl, and N/Ca and positively with Ca and Mg of leaf and fruit tissues. The significance of the correlations depended on the harvest maturity and growing locations. Soil nitrogen application increased Mg and reduced Ca and Cl in lamina but did not influence macro-nutrients in fruit tissues.

Impact of foliar and soil applications of nitrogen on the nutritional status of a young Sitka spruce plantation

In order to ascertain the effect of high nitrogen deposition on trees, a novel method was developed to apply wet-deposited nitrogen to the canopy of a young Sitka spruce plantation. Nets were soaked in salts of ammonium or nitrate and then hung above the tree canopy, enriching the rain passing through. This application method was compared with conventional nutrient additions to the soil. Applications of 10 kg N ha −1 month −1 resulted in enhanced foliar nitrogen levels, no change in potassium or calcium, and a small decrease in magnesium and phosphorus concentrations. Nitrate applications did not increase the low levwl of nitrate reductase activity in the foliage, but there was some evidence for induction in the roots. Sitka spurce plantations in the UK appear to have the capacity to utilise atmospheric inputs of nitrogen without adversely affecting the foliar cation status; however, phosphorus deficiencies could be exacerbated or induced.

Uptake, Storage, and Utilization of Soil-applied Nitrogen by Thompson Seedless as Affected by Time of Application

A grapevine9s need for nitrogen (N) is most critical during the period of rapid shoot growth in spring through bloom and early berry development. Timing of fertilizer applied to the soil necessary to maximize nitrogen in leaf tissue during this period was evaluated in two mature Thompson Seedless vineyards. Application periods, using labeled ammonium sulfate, included budbreak, July, and post harvest in late September. Application in July and September resulted in the highest content of labeled nitrogen in dormant storage tissue, and in leaf tissue during rapid spring growth and at bloom. It is apparent that labeled nitrogen stored in roots, trunk, and canes during dormancy was redistributed to support early spring growth. Nitrogen applied at budbreak had insufficient time for uptake to become a significant fraction of total N in leaf tissue by bloom.