Net fluxes of mineral nutrients,water, and carbohydrate influenced by manganese in root and shoot of Cucumis sativus L. 1

An experiment was conducted with cucumber (Cueumis sativus L., cv. Sumter) plants in the vegetative phase of growth to determine effects of manganese deficiency (0.2 μM Mn) and toxicity (182 μM Mn) on fluxes of several mineral nutrients, water, and carbohydrate in the root and shoot, beginning 43 d after germination. Plants were sampled every three days from 34 to 58 d after germination. First and second derivatives of regression equations were used to estimate fluxes and study source/sink phenomena of dry weight (DW), fresh weight (FW), H₂O, Cu, Fe, Mn, Zn, N, P, and K in root and shoot tissues.

With Mn sufficiency (1.8 μM Mn), both root and shoot acted as sinks for of each of the 10 dependent variables through 58 d. In contrast, Mn deficiency caused net loss of K and N from the root beginning at 53 and 56 d, respectively, and net loss of P and Fe from the shoot beginning at 57 and 58 d, respectively. With Mn toxicity, net loss of Cu, N, and K from the root began at 46, 46, and 51 d, respectively, and net loss of Fe from the shoot began at 55 d. Both Mn deficiency and toxicity increased the shoot:root ratio (S:R) of K and decreased the S:R of Fe, compared to Mn‐sufficiency. Manganese deficiency decreased the S:R of DW and H₂O, and Mn toxicity increased the S:R of FW, DW, H₂0, and N. Under the conditions of this experiment, acute Mn toxicity affected fluxes more severely than did Mn deficiency.     

Diagnosis of the nitrogen status of wheat at tillering and prognosis for maximal grain yield

Abstract

From a field experiment in which wheat was supplied with nitrogen fertilizer at 0, 20, 40, 60, 80, 100, 150, 200, or 400 kg ha^‐1N, a correlation existed between nitrate concentration in wheat stems at tillering and subsequent grain yield. At early tillering, NO₃‐N concentrations around 8,000 μg g^‐1 were indicative of sufficient nitrogen in the crop‐soil system for maximum grain yield.

Averaging the results of this experiment with those from another seven field experiments, it was concluded that at tillering, the prognostic levels of NO₃‐N concentration in stems were: below 4000 μg g^‐1 deficient, between 4000 and 6000 μg g^‐1 intermediate, between 6000 and 10000 μg g^‐1 sufficient and above 10000 excessive for maximum grain yield. These values are applicable in a wide range of water supply conditions and to a number of cereal genotypes.     

Rate of nitrapyrin and soil ph effects on nitrification of ammonium fertilizer and growth and composition of burley tobacco

Abstract

Laboratory and greenhouse experiments were conducted to determine the effects of rate of nitrapyrin and soil pH on nitrification of NH₄ ⁺ fertilizer in soil, and growth and chemical composition of burley tobacco (Nicotiana tabacum L. cv. ‘KY ‐14'). Such experiments were needed to develop information for increasing efficiency of N fertilizer use and to lessen the fertilizer‐induced soil acidity and salt effects on tobacco plants.

Results for laboratory and greenhouse incubations indicated that nitrification proceeeded slowly below pH 5.0 and the nitrapyrin necessary to delay nitrification increased with both increasing soil pH and length of incubation time. Generally, nitrification could be delayed 30 days by nitrapyrin rates of 0.25 or 0.5 μg g^‐1 regardless of soil pH. but rates of 1 μg g^‐1 nitrapyrin or higher were required for 60 days and longer incubation times, particularly at higher soil pH.

Growth and morphology of tobacco plants were either unaffected, or affected positively, by low rates of nitrapyrin (up to 2 μg g^‐1). However, rates of 4 μg g^‐1 and above reduced total plant dry weight, reducing sugars and contents of mineral elements. Concentrations and content of plant NO₃ ^‐ N and Mn were greatly decreased by application of nitrapyrin. Values for most parameters measured increased with increasing soil pH. The data show that low rates of nitrapyrin may be used to alter the ratio of NO₃ ^‐ to NH₄ ⁺ N absorbed by tobacco and possibly improve growth and safety of tobacco.     

Selenium accumulation in a rapid‐cycling Brassica oleracea population responds to increasing sodium seienate concentrations

Because of their short life cycle, rapid‐cycling base populations (RCBP) of Brassica can act as model systems for investigating selenium (Se) metabolism in high sulfur (S) accumulating plants. To establish treatment responses for a B. oleracea RCBP, plants were grown in nutrient solutions containing 0, 3, 6, and 9 mg sodium seienate (Na₂SeO₄) L^‐1. Depletion of Se from nutrient solutions increased linearly with in‐creasing Na₂SeO₄ concentrations. Selenium accumulation ranged from 551 to 1,916 μg Se g^‐1 dry weight for leaf tissue, 267 to 1,165 μg Se g^‐1 dry weight for stem tissue, and 338 to 1,636 μg Se g^‐1 dry weight for root tissue. Selenium additions also resulted in linear increases in S accumulation in leaves and stems. Selenium supplementation has been shown to improve the health of individuals with low Se status. Because Brassica species are important vegetable and forage crops, their enrichment with Se maybe a good delivery system for mammalian diets.     

Quantification of long‐chain fatty acids in dissolved organic matter and soils

The objective was to develop and adapt a versatile analytical method for the quantification of solvent extractable, saturated long‐chain fatty acids in aquatic and terrestrial environments. Fulvic (FA) and humic (HA) acids, dissolved organic matter (DOM) in water, as well as organic matter in whole soils (SOM) of different horizons were investigated. The proposed methodology comprised extraction by dichloromethane/acetone and derivatization with tetramethylammonium hydroxide (TMAH) followed by gas chromatography/mass spectrometry (GC/MS) and library searches. The C_10:0 to C_34:0 methyl esters of n‐alkyl fatty acids were used as external standards for calibration. The total concentrations of C_14:0 to C_28:0 n‐alkyl fatty acids were determined in DOM obtained by reverse‐osmosis of Suwannee river water (309.3 μg g^—1), in freeze‐dried brown lake water (180.6 μg g^—1), its DOM concentrate (93.0 μg g^—1), humic acid (43.1 μg g^—1), and fulvic acid (42.5 μg g^—1). The concentrations of the methylated fatty acids (n‐C_16:0 to n‐C_28:0) were significantly (r² = 0.9999) correlated with the proportions of marker signals (% total ion intensity (TII), m/z 256 to m/z 508) in the corresponding pyrolysis‐field ionization (FI) mass spectra. The concentrations of terrestrial C_10:0 to C_34:0 n‐alkyl fatty acids from four soil samples ranged from 0.02 μg g^—1 to 11 μg g^—1. The total concentrations of the extractable fatty acids were quantified from a Podzol Bh horizon (26.2 μg g^—1), Phaeozem Ap unfertilized (48.1 μg g^—1), Phaeozem Ap fertilized (57.7 μg g^—1), and Gleysol Ap (66.7 μg g^—1). Our results demonstrate that the method is well suited to investigate the role of long‐chain fatty acids in humic fractions, whole soils and their particle‐size fractions and can be serve for the differentiation of plant growth and soil management.     

Co-situs application of controlled-release fertilizers to alleviate iron chlorosis of paddy rice grown in calcareous soil

Abstract

Co-situs is the placement with one application of a sufficient amount of controlled-release fertilizer for an entire growing season at any site, together with seeds or seedlings, without causing fertilizer salt injury. An experiment was conducted to find an efficient method for ameliorating Fe deficiency in two rice cultivars (cv. Tsukinohikari and cv. Sasanishiki) grown in a calcareous soil (pH 9.2, CaCO₃ 384 g kg^?1), which was poor in organic matter (0.1 g kg^?1) and available Fe (3.0 μg g^?1 soil). The field treatments consisted of co-situs application of the following fertilizers: 1) controlled-release NPK fertilizer (CRF-NPK) containing no micronutrients; 2) controlled-release NPK fertilizer containing micronutrients (CRF-M1); and 3) controlled-release NPK fertilizer containing micronutrients (CRF-M2). The main difference between CRF-M1 and CRF-M2 was that the former had larger granules than the latter. All the fertilizers were placed in contact with the roots of rice seedlings at transplanting time. Plants in the CRF-M1 and CRF-M2 treatments had similar lengths, number of stems, leaf age, and leaf color (SPAR value) during the cultivation period. By contrast, plants from the CRF-NPK treatments grew poorly, showed severe chlorosis symptoms of Fe deficiency, and all died on 30 DAT. Plants of both cultivars accumulated more macroand micronutrients with the CRF-M2 treatment than with the CRF-M1 treatment. The grain yield of cv. Tsukinohikari was 0.0, 1,910, and 2,160 kg ha^?1 for the CRF-NPK, CRF-M1, and CRF-M2 treatments, respectively, and 0.0, 2,490, and 2,860 kg ha^?1 for the same treatments for cv. Nihonbare. Chlorosis due to iron deficiency was successfully ameliorated and world-average grain yields were obtained with the co-sites application of both controlled-release fertilizers.     

Aluminum toxicity in plants grown in solution culture

Abstract

Earlirose rice (Oryza sativa L. ) and Hawkeye soybeans (Glycine max L.) were grown in solution culture with A1₂(SO₄)₃ in concentrations of 0, 10^‐6, 10^‐5, 10^‐4, 10^‐3 M. Only at 10^‐4 (slightly) and at 10^‐3 M were there yield depressions due to Al. The threshold concentration of Al for toxicity was about 20 μg/g in rice shoots and about 30 μg/g in soybean leaves. The solution level necessary for these concentrations was 8 μg Al/ml. Plant concentrations which caused severe toxicity were 70 μg Al/g plant with 81 μg Al/ml solution. Most Al remained in roots, but leaves contained more than did stems of soybeans. The high Al decreased Fe, Cu, and Mn concentrations in shoots of rice and decreased Fe, Cu, and Zn in roots of rice. The high Al resulted in decreased Fe and Zn in leaves of soybeans. No Fe deficiency symptoms were present due to the high Al.     

ACCUMULATION OF SULPHUR IN AND ON SCOTS PINE NEEDLES IN THE SUBARCTIC

Total S concentrations of Scots pine (Pinus sylvestris L.) needles studied in the Finnish subarctic (66–70°N, 24–30°E) in 1990/1992 ranged from 573 to 1153 μg g^-1. Levels were found to be ≈ 900 μg g^-1 (i.e. 1.3–1.8 times the ‘normal’ level of 500–700 μg g^-1) in areas where the long-term ambient SO₂ concentration was ≈ 2–5 μg m^-3, particulate SO₄ ^2- ≈ μg m^-3 and total S deposition ≈ 0.5 g m^-2. A statistically significant increase in needle total S concentrations was found towards the east, i.e. towards the smelters of the Kola Peninsula in Russia, which emit SO₂. The increase in needle total S concentrations to over 900 μg g^-1 close to the Russian border is thought to result mainly from exposure to high short-term SO₂ concentrations. The results also suggest that wintertime S deposition may have an impact on the needle total S content. It is suggested that the UNECE long-term critical level of 15 μg SO₂ m^-3 for forestry in boreal and high mountain climates in Europe is too high for the pine forests in the extreme north, where the proportion of dry-deposited S may be 60–80%.     

Mineral element composition of declining and healthy stands of red spruce in western Massachusetts

Abstract

Concentrations of N, P, K, Ca, Mg, and Mn were determined in one‐, two‐, and five‐year‐old needles from upper and lower crowns of declining and healthy red spruce (Picea rubens Sarg.) to assess nutritional deficiencies as causes of severe defoliation in upper‐elevation forests in western Massachusetts. Concentrations of N and K did not differ between stands or positions in crowns but decreased with leaf age. In declining stands, mean Ca concentrations were the same in the upper and lower crowns (3.2 mg g^‐1), whereas in healthy stands, Ca was higher in the lower crown (4.8 mg g^‐1) than in the upper crown (3.9 mg g^‐1). Five‐year‐old needles of healthy trees had higher Ca than those of declining trees (6.0 and 3.8 mg g^‐1, respectively). Mean concentrations of P and Mg in declining trees were 0.9 and 0.5 mg g^‐1, respectively, with each element being at threshold levels of sufficiency. Mean concentrations of P and Mg, respectively, were 0.3 mg g^‐1 and 0.2 mg g^‐1 lower in needles of declining trees than in healthy trees. Five‐year‐old needles of declining trees were lower in P and Mg than those from healthy trees. Mean Mn concentrations were lower in needles of declining trees than in healthy trees (0.4 vs 1.3 mg g^‐1). The results suggest that low P, Mg, and possibly Ca concentrations in needles of declining trees may contribute to the decline.     

COPPER EFFECTS ON PRUNUS PERSICA IN TWO DIFFERENT GRAFTING COMBINATIONS (P. PERSICA × P. AMYGDALUS AND P. CERASIFERA)

Growth, chlorophyll content, biomass dry weight (DW), nutrient uptake and copper (Cu) accumulation were evaluated in BigTop® peach (Prunus persica L. Batsch) grafted onto two different rootstocks [GF677 (P. persica × P. amygdalus) and Mr.S2/5 (P. cerasifera)] when grown in the presence of 0.1, 10 or 100 μM copper sulfate (CuSO₄). Although scion shoot length varied significantly in response to Cu concentration only with Mr.S2/5 rootstock (40%reduction at 100 μM Cu compared with control), Cu concentration in the scion grafted on GF677 was higher (18.2 mg kg^?1) compared to that grafted on Mr.S2/5 (10.5 mg kg^?1). In both graft combinations, the Cu concentrations in leaves were not statistically different although values ranged between 4.7 and 8.1 mg kg^?1. The DW of leaves and stems was not statistically different from control plants in both graft combinations. On the contrary, root DW of Mr.S2/5 increased, about 13% at 10 μM Cu and 43% at 100 μM Cu. In contrast, DW of GF677 roots at higher Cu treatment was significant lower than control. Chlorophyll reduction Cu induced was not found, suggesting that the degradation of these pigments is maintained at low levels. The uptake of sodium (Na), zinc (Zn), and iron (Fe) changed during Cu stress. The different behavior observed between GF677 and Mr.S2/5 regarding Cu accumulation proves that these two rootstocks have a different ability in translocation and accumulation of Cu in presence of this heavy metal. The use of GF677 rootstocks, in substrates particularly rich of Cu, insures a better development of scion growth when compared to Mr.S2/5, but determines a higher Cu concentration in the stem, while Mr.S2/5 seems to be able to stabilize the Cu concentrations in the scion.     

Influence of sulfur deficiency on chlorophyll‐meter readings of corn leaves

Sulfur (S)‐diagnostic tools are essential for rational use of S fertilizers. There is little information about the suitability of leaf greenness intensity to detect S deficiency in corn (Zea mays L.). This work evaluates, under controlled S‐stressed conditions, (1) the performance of leaf greenness intensity as an indicator of the degree of S deficiency in corn, and (2) the advantage of the upper leaves in relation to the middle leaves for S‐deficiency determination. A pot experiment using sand as growth medium was conducted in greenhouse with corn at S rates of 0, 5, 10, 20, and 40 mg kg^–1 and sufficiency of other nutrients. Measurements of aboveground biomass (AB), total nitrogen (N), and S concentrations, and chlorophyll‐meter readings (CMR) in upper and middle leaves, were performed at the growth stages of 6–7, 11–12, and 14–15 fully expanded leaves (V6‐V7, V11‐V12, and V14‐V15, respectively). Sulfur application significantly increased AB, leaf S concentration, and CMR. Significantly positive relationships were obtained between leaf S concentration and CMR. A sulfur‐sufficiency index (SSI) based on CMR measured in upper and middle leaves was significantly associated with AB (R² = 0.58 and 0.62 for the middle and upper leaves, respectively). It is concluded that under sufficiency of other nutrients and high‐S‐stressed conditions, leaf greenness intensity could be a good indicator of corn S status, although little or no advantage was found for taking CMR from the upper leaves.     

Evaluation of N,P, S and B fertilization of Kentucky bluegrass seed in northern Idaho

Abstract

Current nitrogen (N) fertilizer recommendations for Kentucky bluegrass (Poa pratensis L.) seed production in northern Idaho are based on potential yield and annual precipitation. Soil test correlation information collected for other northern Idaho crops provide the basis for P, S and B recommendations. The objective of this paper is to assess the current recommendations with a series of forty field trials conducted on ten sites during four seed production seasons. All field trials were conducted on Alfisols and Mollisols initially containing less than 60 kg N/ha, 3.5 μg/g NaOAc extractable P, 40 kg extractable SO₄‐S/ha and 0.5 μg/g extractable B. Fertilization rates evaluated included: 0, 50, 75, 100, 125, 150 and 200 kg N/ha; 0, 30 and 60 kg P₂O₅/ha; 0, 25, and 50 kg SO₄‐S/ha, and 0 and 1.5 kg B/ha. Five field sites contained the cultivar ‘Argyle’ Kentucky bluegrass seed, while the other five sites contained the cultivar ‘South Dakota’.

Excellent relationships between percent maximum Kentucky bluegrass seed production and the sum of inorganic soil N + fertilizer N applied were observed for the ‘Argyle’ (R²=0.65) and ‘South Dakota’ (R²=0.72) cultivars. Phosphorus applications of 30 kg P₂O₅/ha improved seed yields from 10.0 to 51.6% when initial soil test values were less than 3.0 6 μg/g NaOAc extractable P. When initial SO₄‐S soil values were less than 32 kg/ha fertilizer additions increased seed yields from 12.6 to 107.3%. Boron applications did not improve seed yields. Analysis of these trials indicates that adequate information is available to make satisfactory P, S and B fertilizer recommendations; however, additional soil test correlation information is needed for N recommendations.     

ASSESSMENT OF NITROGEN NUTRITION OF WALNUT TREES USING FOLIAR ANALYSIS AND CHLOROPHYLL MEASUREMENTS

The response of walnut trees to nitrogen (N) availability was studied on 3-year-old pot-grown trees (Juglans major MJ209 L. Juglans regia L.) in a greenhouse and on 10-year-old field grown trees. The greenhouse pot trial included 5 N levels (0.25, 0.5, 1, 2.5 and 5 g N per plant), and the field trial compared walnut trees with or without N₂-fixing intercrops. In the greenhouse trial, the growth of both root and aerial parts was found to be significantly dependent on N availability. The deficiency treatment (0.25 g N/plant) reduced leaf and root dry weights to 30 and 54% of those of the sufficiency treatment (5 g N/plant) values. The analysis of the youngest fully expanded leaf after the end of shoot elongation period was a good indicator of the tree N nutrition level. Severe deficiency corresponded to leaf N contents below 17 g N kg^?1 DM (mean dry matter), light deficiency between 17 and 24, and maximum growth was obtained with 26 g N kg^?1 DM contents. Terminal leaflet chlorophyll measurements were linearly correlated with N concentration expressed on a leaf area basis (g N m^?2, r²=0.73 for greenhouse trees and r²=0.86 for field trees). The chlorophyll meter readings divided by the specific leaf weight were also correlated with N expressed on a weight basis (g N kg^?1 DM, r²=0.73 for greenhouse trees and r²=0.89 for field trees). However, these relationships were found to be dependent of environmental conditions and were different between greenhouse and field grown trees. Relative indices of chlorophyll measurements and of N concentrations were however consistent over the two sites. Chlorophyll meter measurements could therefore be a useful method to assess the N nutrition status of walnut trees at a low cost, provided that some reference trees with sufficient N nutrition are locally available.     

Effect of sulfur rate,application method,and source on yield and mineral content of corn

Abstract

Corn (Zea mays L.) grown on sandy Coastal Plain soils may be subject to sulfur (S) deficiency due to the low levels of available S in the soil. The diagnosis of S deficiency in the field is sometimes ambiguous since mineralization of soil organic matter or root growth into the subsoil may supply adequate S to the crop. Yield response to S fertilizers has been more frequent since incidental additions of S to the soil by air pollution and fertilizer applications have been reduced. This study was conducted to identify S deficiency in corn grown on sandy Coastal Plain soils and to determine the effects of S source, rate and method of application on grain yield. Irrigated corn was grown on Norfolk loamy sand and Tifton loamy sand near Leesburg and Moultrie, Georgia, respectively in 1987. Grain yields were increased with addition of 11 kg S ha^‐1 compared to the check treatment. Increased rates of S up to 88 kg ha^‐1 did not increase grain yields above the 11 kg ha^‐1 rate. There was no difference between banded or broadcast application of (NH₄)₂SO₄ or between elemental S and (NH₄)₂SO₄ as S sources. Earleaf S concentrations of 1.6 g kg^‐1 and extractable soil S concentrations of 4.0 to 8.7 mg kg^‐1 were associated with S deficiency. Visual symtoms of S deficiency were observed in the check treatments throughout the growing season at both experimental sites. The results indicate that visual symptoms and tissue analysis can be used to identify S deficiency. Extractable soil S may be useful in determining the possible response to S fertilizer especially if the subsoil is sampled.     

Optimum nutrient levels in a container growing medium determined by a saturated aqueous extract

Abstract

Red pine (Pinus resinosa Ait.) seedlings were grown for 15 weeks over a range of nutrient regimes to calibrate a test procedure used for monitoring nutrient status of a common container growing medium. The test was based on a saturated aqueous extract of the growing medium, obtained by suction displacement. Seedling growth and nutrition exhibited typical responses of deficiency, sufficiency, luxury consumption and toxicity over the range of substrate fertility examined. Water extractable nutrients of the growing medium were related to yield and nutrient uptake of the seedlings. Ranges of nutrient levels associated with maximum dry matter production were selected as provisional values for optimum growth of containerized red pine seedlings. The following critical nutrient levels were considered optimum for red pine seedlings managed under similar cultural conditions: 15–65 ppm N (as NH₄ ⁺), 35–95 ppm P, 25–115 ppm K, 30–60 ppm Ca, 15–35 ppm Mg, and electrical conductivity of 1.0–2.2 dS/m.     

Tolerance of rice plants to trace metals

Abstract

The tolerance of rice (Oryza sativa L. C.V. Earlirose) to various trace metal excesses was tested to determine if high levels of the trace metals found in some field‐grown plants were at toxicity levels. In one experiment, levels of 2200 μg Zn/g dry weight, 44 μg Cu/g dry weight, 4400 μg Mn/g dry weight, and 32 μg Pb/g dry weight in shoots of young plants had no adverse effects on vegetative yields. A level of 3160μgZn/ g dry weight decreased yields about 40% (P = . 05). In another test 51 μg Cu/g dry weight or 94 μg Pb/g dry weight did not decrease vegetative yields. Boron supplied at 10^‐3 MH₃BO₃ not only caused no toxicity but resulted in only 144 μg B/g dry weight in shoots. Root levels of Zn were about equal to those in shoots; Mn levels were lower in roots than in shoots (1/4 to 1/10); B levels were generally low in both shoots and roots with roots 1/10 that of shoots; Cu levels were higher in roots than in shoots. Rice was tolerant of a high level of Cr. The tolerance of rice to high levels of some trace metals in these experiments may be related to high P levels in plants.     

Impact of sulfur applications on the agronomic performance of rapeseed–clover mixtures

Rapeseed (Brassica napus L.) is a crop requiring high levels of nitrogen (N) fertilizer for growth and to optimize yield and seed quality. To limit the environmental pollution associated with intensive N fertilizer use, rapeseed–clover (Trititcum incarnatum L.) mixtures were grown in lysimeters under low N conditions (100 kg N ha⁻¹). Considering the high sulfur (S) requirements of both rapeseed and clover, two inputs of S fertilizer (30 and 60 kg S ha⁻¹) were applied. The effects S input on the agronomic performance of rapeseed in mixture and monocrops considered as reference, the N₂‐fixing capacity of clover, and the leaching of nitrate and sulfate were monitored. This study showed that the N₂‐fixing capacity (%Ndfa) of clover was improved (1.3‐fold) when it was grown in mixture with rapeseed at S60. However, irrespective of the type of cropping (monocrops or mixtures) and S application level (30 or 60 kg S ha⁻¹), the biomasses and total N and S contents of both plants were not significantly different, nor was the rapeseed seed quality. Moreover, the yield of rapeseed grown in mixture at S60 was significantly lower than the yield of rapeseed grown as a monocrop (331.5 ± 9.8 versus 380.8 ± 3.5 g DW m⁻², respectively). The results demonstrate that, in our field conditions, rapeseed mixed with clover required only 30 kg S ha⁻¹ to maintain yield and seed quality, despite the high S needs of both plants. More surprisingly, compared to the rapeseed monocrop, the rapeseed–clover mixture led to an increase in N (‐N) and S (‐S) leaching during the early winter period of cultivation.     

Estimating nitrogen requirements for irrigated malting barley

Abstract

The production of marketable malting barley requires careful N management to meet the quality standards set by the malting industry. Nine field trials were conducted over an eight‐year period at four locations to develop N fertilization guidelines for irrigated malting barley. Residual soil NO₃‐N (0 to 60 cm) ranged from 15 to 103 kg N/ha. Nitrogen fertilizer was applied preplant as either urea or NH₄NO₃ at rates ranging from 0 to 269 kg N/ha. Maximum yields were obtained when the sum of residual plus applied N (available N) was above 110 kg N/ha. However, the percentage of plump kernels generally fell below acceptable levels (85%) when available N exceeded 135 kg N/ha. Grain protein exceeded acceptable levels (12%) when available N was above 210 kg N/ha. Stem NO₃‐N sufficiency levels were determined from high‐yielding barley with acceptable quality parameters. At the three‐leaf stage, the barley stem NO₃‐N sufficiency level was approximately 6,000 μg/g and decreased to about 1,000 μg/g at the eight‐leaf stage.     

Potassium uptake characteristics of prunus rootstocks: Influence of solution Ca/Mg ratios and solution nickel

Abstract

Nutrient solution experiments were conducted in the growth chamber to study the influence of rootstock, solution Ca/Mg ratios and solution nickel on K uptake. The experimental plants were one‐year‐old prune trees: ‘French’ prune (Prunus domestica L.) scions grafted on Myrobalan 29C (P. cerasifera Ehrh.), Marianna 2624 (P. cerasifera x P. munsoniana?) or Nemaguard (P. persica x P. davidiana) rootstocks. Ion uptake parameters Imax, Km, and Cmin were calculated from ion depletion measurements over a 6 to 10‐hr period.

With K solution concentrations initially adjusted to 100 μM, K uptake rates of Prunus rootstocks were constant down to approximately 20–30 μM, then declined. Rootstocks were able to deplete solution K to concentrations less than 1 μM. There were no significant differences in K uptake parameters among the rootstocks tested.

Varying solution Ca/Mg ratio from 2.75/1 to 1/4 (Ca + Mg = 3.75 mM) had no effect on K uptake. Potassium uptake rates of Myrobalan 29C rootstocks in the presence of 100 μM nickel were not significantly different from those in the absence of nickel. Rates of nickel uptake were significantly lower than those of K. After eight days of pretreatment in solutions adjusted daily to 100 μM Ni(NO₃)₂, prune leaves began to show signs of interveinal chlorosis. Potassium uptake by nickel pretreated trees was not significantly different from that by control trees. Results are discussed in relation to field observations of K deficiency in prune orchards.     

Citrus leaf nutrient status: A critical evaluation of guidelines for optimal yield in Israel

Maintaining orchards with trees at optimal leaf nutrient concentrations is one of the key issues for maximizing yield. Experiments for evaluating and updating guidelines are very rare since they require several years of field experiments with mature fruit‐bearing trees. In the present paper, we first evaluated the Israeli guidelines for citrus by comparing them to the Israeli orchard leaf mineral status using a 10‐year leaf‐mineral database (results of 20 244 leaf analyses from commercial orchards all over Israel). Then, we created an updated guideline using a second database (the Israeli National Wastewater Effluent Irrigation Surveys database; INWEIS). This database summarizes yield and leaf mineral concentrations of commercial orchards from all over Israel. The data were collected from 122 orchards: 39 orchards of “Oroblanco” Pomelit (Citrus grandis), 33 orchards of “Michal” mandarin (C. reticulata), 30 orchards of “Star Ruby” grapefruit (C. paradise), and 20 orchards of “Shamouti” oranges (C. sinensis) over a 7‐year period. Based on the first database, there was a disagreement between recommendations and the leaf nutrient status (e.g., the Israeli Ministry of Agriculture recommendations were higher than orchard median values), which indicated that the growers and/or the recommendations need to be corrected. Based on the INWEIS database, a new guideline was set. It was found that the optimal leaf nutrient concentrations for grapefruit trees are 1.7% to 2.1% dry weight (DW) for N, 0.08% to 0.010% DW for P, 0.37% to 0.48% DW for K, and 0.33% to 0.45% DW for Mg. For orange trees, the optimal leaf nutrient concentrations are 1.9% to 2.3% DW for N, 0.11% to 0.14% DW for P, 0.80% to 1.00% DW for K, and 0.19% to 0.26% DW for Mg. For mandarin trees, the optimal leaf nutrient concentrations are 2.0% to 2.4% DW for N, 0.09% to 0.12% DW for P, 0.55% to 0.69% DW for K, and 0.19% to 0.26% DW for Mg. Maintaining leaf nutrient concentrations within these ranges will support maximal yields of 110 to 120 t ha^–1 for grapefruit, 65 to 70 t ha^–1 for orange, and 60 to 70 t ha^–1 for mandarin cultivars.