Effect of seed zinc content on grain yield and zinc concentration of wheat grown in zinc‐deficient calcareous soils

Field experiments were carried out to study the effect of different seed‐zinc (Zn) content on grain yield and grain Zn concentration in a bread wheat cultivar Atay 85 grown in a severely Zn‐deficient soil under rainfed and irrigated conditions for two years. Three groups of seeds with Zn contents of 355, 800, and 1,465 ng Zn seed^‐1 were obtained through different number of foliar applications of ZnSO₄.7H₂O in the previous crop year. Experiments were carried out with 23 kg Zn ha^‐1 (as ZnSO₄.7H₂O) and without Zn fertilization to the soil. Grain yield from seeds with 800 and 1,465 ng Zn seed^‐1 content was significantly higher than that from low seed‐Zn, especially under rainfed conditions. In the first year, under rainfed and Zn‐deficient conditions, yield of plants grown from the highest seed‐Zn content was 116% higher than the yield of plants grown from the low seed‐Zn content. However, in the first year soil‐Zn application combined with low‐Zn seed resulted in a yield increase of 466% compared to nill Zn treatment with low‐Zn seed, indicating that higher seed‐Zn contents could not compensate for the effects of soil Zn application. Soil Zn application significantly increased Zn concentrations in shoot and grain. However, the effect of different seed Zn contents on Zn concentrations of plants was not significant, probably due to the dilution of Zn in tissues resulting from enhanced dry matter production. The results presented show that wheat plants grown from seed with high Zn content can achieve higher grain yields than those grown from the low‐Zn seed when Zn was not applied to the soil. Therefore, sowing seeds with higher Zn contents can be considered a practical solution to alleviate Zn deficiency problem, especially under rainfed conditions in spite of it being insufficient to completely overcome the problem.     

Effects of zinc fertilization and irrigation on grain yield and zinc concentration of various cereals grown in zinc‐deficient calcareous soils

Effects of varied irrigation and zinc (Zn) fertilization (0, 7, 14, 21 kg Zn ha^‐1 as ZnSO₄7.H₂O) on grain yield and concentration and content of Zn were studied in two bread wheat (Triticum aestivum), two durum wheat (Triticum durum), two barley (Hordeum vulgare), two triticale (xTriticosecale Wittmark), one rye (Secale cereale), and one oat (Avena sativa) cultivars grown in a Zn‐deficient soil (DTPA‐extractable Zn: 0.09 mg kg^‐1) under rainfed and irrigated field conditions. Only minor or no yield reduction occurred in rye as a result of Zn deficiency. The highest reduction in plant growth and grain yield due to Zn deficiency was observed in durum wheats, followed by oat, barley, bread wheat and triticale. These decreases in yield due to Zn deficiency became more pronounced under rainfed conditions. Although highly significant differences in grain yield were found between treatments with and without Zn, no significant difference was obtained between the Zn doses applied (7–21 kg ha^‐1), indicating that 7 kg Zn ha^‐1 would be sufficient to overcome Zn deficiency. Increasing doses of Zn application resulted in significant increases in concentration and content of Zn in shoot and grain. The sensitivity of various cereals to Zn deficiency was different and closely related to Zn content in the shoot but not to Zn amount per unit dry weight. Irrigation was effective in increasing both shoot Zn content and Zn efficiency of cultivars. The results demonstrate the existence of a large genotypic variation in Zn efficiency among and within cereals and suggest that plants become more sensitive to Zn deficiency under rainfed than irrigated conditions.     

Differences in shoot growth and zinc concentration of 164 bread wheat genotypes in a zinc‐deficient calcareous soil

Abstract

A greenhouse experiment was carried out to study severity of the zinc (Zn) deficiency symptoms on leaves, shoot dry weight and shoot content and concentration of Zn in 164 winter type bread wheat genotypes (Triticunt aestivum L.) grown in a Zn‐deficient calcareous soil with (+Zn=10 mg Zn kg^?1 soil) and without (‐Zn) Zn supply for 45 days. Tolerance of the genotypes to Zn deficiency was ranked based on the relative shoot growth (Zn efficiency ratio), calculated as the ratio of the shoot dry weight produced under Zn deficiency to that produced under adequate Zn supply. There was a substantial difference in genotypic tolerance to Zn deficiency. Among the 164 genotypes, 108 genotypes had severe visible symptoms of Zn deficiency (whitish‐brown necrotic patches) on leaves, while in 25 genotypes Zn deficiency symptoms were slight or absent, and the remaining genotypes (e.g., 31 genotypes) showed mild deficiency symptoms. Generally, the genotypes with higher tolerance to Zn deficiency originated from Balkan countries and Turkey, while genotypes originating from the breeding programs in the Great Plains of the United States were mostly sensitive to Zn deficiency. Among the 164 wheat genotypes, Zn efficiency ratio varied from 0.33 to 0.77. The differences in tolerance to Zn deficiency were totally independent of shoot Zn concentrations, but showed a close relationship to the total amount (content) of Zn per shoot. The absolute shoot growth of the genotypes under Zn deficiency corresponded very well with the differences in tolerance to Zn deficiency. Under adequate Zn supply, the 10 most Zn‐ inefficient genotypes and the 10 most Zn‐efficient genotypes were very similar in their shoot dry weight. However, under Zn deficiency, shoot dry weight of the Zn‐efficient genotypes was, on average, 1.6‐fold higher compared to the Zn‐inefficient genotypes. The results of this study show large, exploitable genotypic variation for tolerance to Zn deficiency in bread wheat. Based on this data, total amount of Zn per shoot, absolute shoot growth under Zn deficiency, and relative shoot growth can be used as reliable plant parameters for assessing genotypic variation in tolerance to Zn deficiency in bread wheat.     

Effect of ammonium chloride,ammonium sulphate,and sodium nitrate on take‐all and grain yield of wheat grown on soils in South‐western Australia

Five field experiments are described which measured the effect of three sources of nitrogen (N) fertilizer, applied at 45 kg N/ha, on the incidence of take‐all and grain yield of wheat. The N fertilizers were ammonium sulphate, ammonium chloride, and sodium nitrate. Compared with the Nil N treatment, ammonium‐nitrogen fertilizer, either as ammonium sulphate (ASdr) or ammonium chloride (ACdr) drilled with the seed, lowered the severity of take‐all. Sodium nitrate topdressed (SNtd) to the soil surface reduced the severity of take‐all in three of five experiments, while ammonium sulphate topdressed (Astd) reduced the severity in four of the five experiments. Ammonium sulphate and ammonium chloride drilled with the seed were equally effective in reducing the severity of take‐all in three of the five experiments. However, ACdr was more effective than ASdr in reducing the severity of take‐all in one experiment whereas ASdr was more effective than ACdr in another experiment. In these two experiments (1 and 5), the effects of the reduction in take‐all severity between the ASdr and ACdr treatments did not affect grain yield. The results suggest that grain yield losses from take‐all are most severe where wheat plants are deficient in N. Chloride containing fertilizers are unlikely to control take‐all disease of wheat on soils of southwestern Australia.     

Effect of levels of take‐all and phosphorus fertiliser on the dry matter and grain yield of wheat

In a field experiment with wheat (Triticum aestivum L.), the effect of the percentage severity of take‐all on the production of dried tops and grain and the kernel weight (mg/seed) was measured when different amounts of phosphorus (P) fertiliser were applied. The soil was severely P deficient. The amounts of P fertitiser varied from nil P (deficient) to 40 kg P/ha (adequate) applied annually. The levels of Gaeumannomyces graminis tritici (Ggt) were generated by four cropping sequences. The levels of percent severity of Ggt on plant roots ranged from low (<10% of wheat plant roots infected) to high (70% of roots infected by Ggt). Yield of dried tops, grain, and kernal weight, all increased as the level of P applied increased, but the amount of Ggt infection decreased. No grain was produced where no P was applied. The percentage increase in yield due to declines in the severity of take‐all was greater as the level of P applied increased. Increasing levels of P fertiliser help control the severity of Ggt (%) only where the initial level of Ggt with nil P fertiliser are moderate to low. Where the levels of Ggt severity are >65% the effectiveness of P in reducing the levels of Ggt severity rapidly declined. The percentage severity of Ggt affected the efficiency of plants to use P fertilisers. For each cropping sequence, a Mitscherlich function described the grain yield response to P fertiliser. The maximum grain yield (A coefficient) and the curvature coefficient (C) both declined with increases in the level of Ggt severity (%). For example, the C was significantly reduced from 0.134±0.03 for the least Ggt severity (%) to 0.00446±0.001 where Ggt was not controlled. The kernal weight (mg/seed) was increased by P application and decreased by Ggt infection.     

Effect of zinc application methods on apparent utilization efficiency of zinc and phosphorus fertilizers under basmati rice–wheat rotation

To examine the effect of zinc (Zn) application method on the utilization of phosphorus (P) from applied P fertilizer, a field experiment was conducted on basmati rice–wheat rotation with combinations of Zn levels (0, soil application of 2.5 kg Zn ha ^{– 1} and two foliar applications of 2.0 kg Zn ha ^–1) and P levels (0, soil application of 8.7, 17.5 and 26.2 kg P ha ^–1). The highest pooled grain yields of basmati rice and wheat were obtained with soil application of 17.5 kg P ha ^–1 and foliar applications of 2 kg Zn ha ^–1. Foliar applications of Zn increased the P concentration in grain and straw and the total P uptake by basmati rice and the P concentration in flag leaves of wheat significantly, while soil or foliar application of Zn increased the total P uptake of wheat. Phosphorus application increased the Zn concentration in flag leaves, grain and straw of basmati rice and in grain and straw of wheat and the total Zn uptake of both crops. Phosphorus levels up to 17.5 kg P ha ^–1 increased utilization efficiency of soil or foliar application of Zn. Zinc application increased the P utilization efficiency of basmati rice and wheat up to 17.5 kg P ha ^–1 level; foliar Zn application was more effective in a wheat crop than a rice crop.     

Yield of iron‐sprayed and non‐sprayed strawberry cultivars grown on high ph calcareous soil

Abstract

Iron (Fe) deficiency chlorosis (FeDC) results in extensive reduction in yield of strawberry (Fragaria x ananassa Duch.) grown on high pH calcareous soils. Three cultivars differing in response to FeDC were grown on a high pH (8.2) calcareous soil (25.4% calcium carbonate equivalent in surface 20 cm) in the field (Choueifat, coastal area of Lebanon) to determine the effects of FeDC on fruit yield of cultivars sprayed with FeEDDHA [ferric ethylene‐diiminobis (2‐hydroxyphenyl) acetate]. The unsprayed plots were used as a control. No significant interaction (P<0.05) between cultivars x FeEDDHA spray treatment, and no significant differences (P<0.05) between one and two FeEDDHA spray(s)/week treatment was noted for visual FeDC, fruit number, and fruit yield. Sprayed cultivars once a week produced higher yields than unsprayed ones; overall increases were 33% (13% for ‘Motto’, 30% for ‘Chandler’, and 56% for ‘Douglas'). Even though only slight FeDC was noted on the ‘Motto’ cultivar receiving no Fe EDDHA spray, fruit yields were increased when sprayed with FeEDDHA. However, significant increases in yield for ‘Chandler’ and ‘Douglas’ cultivars with severe FeDC ratings were rioted when sprayed with FeEDDHA.     

Effect of ammonium chloride,ammonium sulphate and sodium nitrate on take‐all and grain yield of wheat in southwestern Australia

Five field experiments measured the effect of three sources of nitrogen (N) fertilizer, applied at 45 kg N/ha, on the incidence of take‐all and grain yield of wheat. The N fertilizers were ammonium sulphate, ammonium chloride and sodium nitrate. Compared with the nil N treatment, ammonium nitrogen fertilizer, either as ammonium sulphate (ASdr) or ammonium chloride (ACdr) drilled with the seed, lowered the severity of take‐all. Sodium nitrate topdressed (SNtd) to the soil surface reduced the severity of take‐all in three of the five experiments, while ammonium sulphate topdressed (AStd) reduced the severity in four experiments. Ammonium sulphate and ammonium chloride drilled with the seed were equally effective in reducing the severity of take‐all in three of the five experiments. However, ACdr was more effective than ASdr in reducing the severity of take‐all in one experiment, whereas ASdr was more effective than ACdr in another experiment. In experiments 1 and 5, the reduction in take‐all severity between the ASdr and ACdr treatments did not affect grain yield. Results suggested that grain yield losses from take‐all are most severe where wheat plants are deficient in N. Fertilizers containing chloride are unlikely to control take‐all disease of wheat on soils of southwestern Australia.     

Manganese‐iron relationship in soybean grown in calcareous soils 1

Although a positive response to iron (Fe) is, usually, expected in calcareous soils; this has not been always the case; and in some instances a depressing effect has been observed. An induced micronutrient imbalance is suspected. This experiment was designed to study the effect of Fe fertilizer on the plant micronutrients. Twenty three highly calcareous soils (18–46% calcium carbonate equivalent; pH 7.7–8.4; and a wide range of extractable Fe) from southern Iran were used in an eight‐week greenhouse experiment to study the effect of Fe fertilizers on soybean [Glycine max (L.) Merr.] growth and chemical composition. The statistical design was a 23 × 3 factorial arranged in a completely randomized block with three replications. Treatments consisted of 23 soils and three levels of applied Fe (0, 10, and 20 mg Fe/kg as FeEDDHA). Uniform doses of nitrogen (N), phosphorus (P), copper (Cu), manganese (Mn), and zinc (Zn) were applied to all pots. Dry matter (DM) and micronutrients concentrations and uptakes of plant tops were determined and used as the plant responses. Application of Fe either had no significant effect on DM or even decreased it. The plant concentration and uptake of Fe increased significantly in all soils. The concentrations and uptakes of Cu and Zn did not change but those of Mn decreased significantly. The negative effect of Fe application was, therefore, attributed to the interference of Fe with Mn nutrition. The mechanism involved appears to be the restriction in Mn translocation from soil to root and/or from root to the plant tops.     

Effect of extractable zinc,phosphorus, and soil ph on zinc concentrations in leaves of field‐grown corn

Abstract

The variability in corn yield responses to applications of Zn fertilizer appears to be associated with several complex soil and climatic factors that affect the availability of endogenous soil Zn to the crop under specific conditions. Among the soil chemical properties that influence availability of endogenous Zn are soil pH, organic matter content, and extractable P. Over a period of several years, soil and plant analysis data were collected from 54 field experiments, field trials, and diagnostic visits to producer's fields. These data were subjected to multiple regression analysis, resulting in an equation: Zn_leaf = 37.14 + 1.513 Zn_st ‐4.04 pH_st ‐ 1.791 ln(P_st/100) where Zn_st, pH_st, and P_st were 0.1N HC1 extractable soil Zn (kg/ha), 1:1 soil‐water pH, and Bray's 1 extractable soil P (kg/ha), respectively. These factors accounted for 67% of variation in leaf Zn, which was a large portion of the variability in Zn_leaf considering that climatic conditions, management levels, and varietal differences were uncontrolled in most instances. Using the previously published critical level in the leaf opposite and below the ear as 17 μg Zn/g, these data can be used to set required soil test levels of Zn at different levels of extractable P and soil pH. Inadequate levels of extractable Zn would range from 2.5 (at pH 6.0, P = 70 kg/ha) to, 9.5 kg/ha (at pH 7.5, P = 420 kg/ha).     

Extractability of previously‐applied zinc as influenced by properties of calcareous soils

Abstract

The recovery of applied zinc (Zn) by plants is relatively small. Coupled with lack of leaching, this leads to accumulation of Zn in topsoil which may result in unfavorable growth conditions for the subsequent plants. Different extractants may be used for assessing the Zn status of soils previously treated with Zn sources. The extractability of retained Zn is influenced by soil properties. This experiment was conducted to study the influence of selected properties of calcareous soils on extractability of Zn by three popular Zn soil tests. Twenty samples from surface horizons (0–20 cm) of highly calcareous soils of southern Iran (pH 7.9 to 8.5; calcium carbonate equivalent 16 to 58%) previously treated with three levels of Zn (0, 10, and 20 mg Zn kg^‐1 soil as ZnSO₄#lb7H₂O) in triplicate and under one crop of corn (Zea mays L.) were extracted with DTPA, EDTA‐(NH₄)₂CO₃ and Na₂‐EDTA. Extractability (EXT) in a particular extractant was defined as the slope of the regression line, relating extractable Zn of each soil to the rate of applied Zn, multiplied by 100. The EXT values of soils ranged from 24.9 to 73.0% for DTPA, 47.2 to 84.4% for EDTA‐(NH₄)₂CO₃, and 28.2 to 56.7% for Na₂‐EDTA. Stepwise regression equations showed that cation exchange capacity (CEC) and calcium carbonate equivalent (CCE) followed by clay content were the most influential soil properties in EXT of retained Zn of highly calcareous soils. The EXT values decreased with increase in CEC, and CCE but increased with increase in clay.     

Influence of split‐applied nitrogen on grain yield and protein content in ten grain sorghum culti‐vars 1

More information on the response of newly developed or introduced grain sorghum cultivare to split‐applied nitrogen (N) in semi‐arid rainfed agriculture is needed. Therefore, the influence of four split‐applied N schedules (100/0, 66/34, 50/50, and 34/66) on six American (SC 283, SC 274, SC 669, B 66181, SC 33, and RTam 428), and four West African (CSm 63, 1S 6704c, 1S 7173c, and 1S 7419c) grain sorghum cultivars was evaluated. The split‐applied N significantly increased grain yield and percent protein in grain sorghum over a one‐time application of N. The increase in yield and protein content varied among varieties and schedules of N application. Varieties SC 574, RTam 428, and Csm 63 at split‐applied schedules of 66/34, 50/50, and 34/66, respectively, gave the highest yield over one‐time application of N. Similar differences in percent protein in grain among cultivars due to split‐applied N were observed.     

Effect of a decade-long chemical fertilizers and amendments application on potassium fractions and yield of maize​–wheat in an acid Alfisol

Effect of long-term addition of chemical fertilizers with or without amendments was studied on different forms of potassium and the yield of maize and wheat. Continuous application of chemical fertilizers and amendments for 40 years influenced different fractions of potassium significantly. Integrated use of a balanced dose of chemical fertilizer, with farmyard manure (FYM) or lime, sustained higher yields of maize and wheat in comparison to inorganic fertilizers alone. Application of urea (100%) N alone for 40 years resulted in zero yield level. Continuous application of chemical fertilizers either alone or in combination with FYM or lime influenced different fractions of potassium significantly. Continuous cropping without fertilization resulted in depletion to the order of 21.5%, 16.6%, 11.7%, and 5.5% in water-soluble, exchangeable, 0.5 N HCl extractable, and non-exchangeable K, respectively. Different fractions of potassium were found to be positively and significantly correlated with grain and stover/straw yield of maize and wheat.     

Influence of air drying and soil gas‐phase carbon dioxide on DTPA‐extractable iron in calcareous soils

Abstract

The extraction of a field‐moist soil with DTPA will result in a level of extractable iron (Fe) lower than that of the air‐dried soil. Soil gas‐phase carbon dioxide (CO₂) levels may be considerably higher than ambient atmospheric levels, especially in wet soils in the field. This study was undertaken to determine whether gas‐phase CO₂ level influences the quantity of Fe extracted by DTPA. Three moist calcareous soils were incubated for 21 days, each at three different partial pressures of CO₂, after which the moist soils were extracted with DTPA. A sample of each soil was also air dried, and was subsequently extracted with DTPA. In each case, DTPA‐extractable Fe from the moist sample was lower than that from the air‐dried sample; however, DTPA‐extractable Fe increased with increasing CO₂ partial pressure of in the moist soils. DTPA‐extractable Fe concentration for a given soil following air drying was not significantly influenced by the CO₂ partial pressure during incubation of the originally field‐moist soil. DTPA‐extract pH of the moist soils followed the same trend as soil‐solution pH (i.e., as CO₂ concentration of the soil gas‐phase increased, soil solution pH and DTPA extract pH both decreased); however, the slope of the pH versus log P_CO2 curve was less pronounced in the DTPA extract due to the buffering capacity of the triethanolamine. From this study, it is concluded that elevated soil gas‐phase CO₂ partial pressure does not contribute to the lower level of DTPA‐extractable Fe observed when the extraction is performed on a field‐moist versus an air‐dried soil; increased CO₂ partial pressure actually resulted in a slight increase in concentration of DTPA‐extractable Fe obtained from a field‐moist soil.     

Behavior of iron‐supplying materials in incubated calcareous soils 1

Two Fe chlorosis‐inducing calcareous soils were incubated for up to 5 months, at room temperature and field capacity, with Fe‐EDDHA, Fe‐DTPA, FeSO₄, an amino acid chelate “Fe‐Metalosate”;, an oxide “Micronized‐Iron”;, and a precipitated Fe‐S compound “Iron‐Sul”;. Other treatments included DTPA chelate alone, elemental S and H₂SO₄ at comparable rates. Both water‐soluble, and DTPA‐extractable Fe fractions were measured periodically from each sample. All water‐soluble sources decreased with time. Soluble Fe was highest after Fe‐EDDHA addition but was not detectable after “Fe‐Metalosate”; and FeSO₄. Acidification to neutralize CaCO₃ significantly increased DTPA‐extractable Fe, which remained high with increasing incubation time. “Micronized‐Iron”; and S had only a slight effect on DTPA‐ extractable Fe. Though Fe‐EDDHA is the most efficient Fe material, pelleted acidified Fe sources, i.e., “Iron‐Sul”;, may be more economical for some crops in the long term.     

Time of availability influences mixed‐nitrogen‐induced increases in growth and yield of wheat 1

Previous studies have indicated that under hydroponic conditions, spring wheat (Triticum aestivum) plants produce higher grain yields, more tillers, and increased dry matter when continuously supplied with mixtures of NO₃ and NH₄ than when supplied with only NO₃. The objective of this study was to determine if mixed N needs to be available before or after flowering, or continuously, in order to elicit increases in growth and yield of wheat. During vegetative development, plants of the cultivar ‘Marshal’ were grown in one of two nutrient solutions containing either a 100/0 or 50/50 mixture of NO₃ to NH₄ and, after flowering, half the plants were switched to the other solution. At physiological maturity, plants were harvested, separated into leaves, stems, roots, and grain and the dry matter and N concentration of each part determined. Yield components and the number of productive tillers were also determined. Availability of mixed N at either growth stage increased grain yield over plants receiving continuous NO₃, but the increase was twice as large when the mixture was present during vegetative growth. When the N mixture was available only during vegetative growth the yield increase was similar to that obtained with continuous mixed N. The yield increases obtained with mixed N were the result of enhanced tillering and the production of more total biomass. Although plants receiving a mixed N treatment accumulated more total N than those grown solely with NO₃, the greatest increase occurred when mixed N was available during vegetative growth. Because availability of mixed N after flowering increased the N concentration over all NO₃ and pre‐flowering mixed N plants, it appears that the additional N accumulation from mixed N needs to be coupled with tiller development in order to enhance grain yields. These results confirm that mixed N nutrition increases yield of wheat and indicate that the most critical growth stage to supply the N mixture to the plant is during vegetative growth.     

Short‐term relationships between membrane permeability and growth parameters in three tomato cultivars grown at low and high zinc

Abstract

An experiment was carried out in a controlled temperature (CT) room for five weeks with tomato cvs., Moneymaker, Liberto, and Calypso, to investigate possible relationships between zinc (Zn) deficiency or toxicity and electrolyte leakage in plant leaves. The concentrations of Zn in nutrient solution were 0.01, 0.5, and 5.0 mg L^?1, respectively. There were significant reductions in the dry matter and chlorophyll content of all three cultivars grown both at 0.01 (low) and 5 mg L^?1 (high) Zn compared to 0.5 mg L^?1. The concentration of Zn at 0.01 mg L^?1 was not sufficient to provide for optimal plant growth, while 5 mg L^?1 in nutrient solution was detrimental to plant growth for all three cultivars. Dry matter production was generally lowest in the plants grown at low (0.01 mg L^?1) Zn except for Moneymaker where the lowest biomass was in the high Zn treatment. Zinc concentration was increased in the leaves and roots with increasing Zn concentration in nutrient solution. Phosphorus concentration was toxic in the leaves of the plants grown at low (0.01 mg L^?1) and was deficienct at high Zn (5 mg L^?1). The electrolyte leakage (%) gradually increased in the plants grown at low and high Zn concentrations and these increases were greatest in the leaves of plants grown at low Zn (except for Moneymaker grown at high Zn where reduction in dry matter was less). The best results for all growth parameters tested were for the plants grown at 0.5 mg L^?1 Zn. The results of this short‐term experiment show that electrolyte leakage which is relatively simple and easy to measure may be a good indicator of cultivar tolerance to Zn deficiency and toxicity.     

Effects of extraction period and soil.‐solution ratio on the amount of zinc extracted from soils by different extractants

Abstract

Investigations have examined the effects of extraction period and soil:solution ratio on the extraction of zinc from some New Zealand soils by EDTA, DTPA, HCl, Ca(NO₃)₂ and CH₃COONH₄. A high proportion of the zinc extracted by EDTA, DTPA, HCl, and Ca(NO₃)₂ was extracted rapidly, within the first 0.5 h, followed by small increases over the next 15 h. An exception occurred with a soil containing iron/manganese concretionary material. In this soil, with both EDTA and DTPA, there were significant increases in the amount of zinc extracted between 1 and 8 h. The amounts of zinc extracted by CH₃COONH₄ increased gradually with the time of extraction up to approximately 4 h.

Substantial increases in the amounts of zinc extracted with HCl, Ca(NO₃)₂ and CH₃COONH₄ were obtained by increasing the soil:solution ratio from 1:2.5 to 1:10. However, soil:solution ratio has little effect on the amounts of zinc extracted by EDTA or DTPA.     

Predicting grain yield and protein content in winter wheat at different N supply levels using canopy reflectance spectra

A field experiment using a split-plot randomized complete block design with three replications was carried out to determine relationships between spectral indices and wheat grain yield （GY）, to compare the performance of four vegetation indices （VIs） for GY prediction, and to study the feasibility of VI to estimate grain protein content （GPC） in winter wheat. Two typical winter wheat （Triticum aestivum L.） cultivars ＇Xuzhou 26＇ （high protein content） and ＇Huaimai 18＇ （low protein content） were used as the main plot treatments and four N rates, i.e., 0, 120, 210, and 300 kg N ha^-1, as the sub-plot treatments. Increasing soil N supply significantly increased GY and GPC （P ≤ 0.05）. For the two cultivars combined, significant and positive correlations were found between four VIs and GY, with the strongest relationship observed when using the green ratio vegetation index （GRVI） at mid-filling. Cumulative VI estimates improved yield predictions substantially, with the best interval being heading to maturity stage. Similar results were found between VI and grain protein yield. However, when using cumulative VI, GPC showed no significant improvement. The strong relationship between leaf N status and GPC （R2 =0.9144 for ＇Xuzhou 26＇ and R2 = 0.8285 for ＇Huaimai 18＇） indicated that canopy spectra could be used to predict GPC. The strong fit between estimated and observed GPC （R2 = 0.7939） indicated that remote sensing techniques were potentially useful predictors of grain protein content and quality in wheat.     

Effects of phosphorus application method and rate on furrow‐irrigated ridge‐tilled grain sorghum

Conservation tillage systems, including ridge‐tillage, have become increasing popular with producers in the central Great Plains because of their effectiveness in controlling soil erosion and conserving water. A major disadvantage of the ridge system is that nutrient placement options are limited by lack of any primary tillage options. The objective of this research was to investigate the effects of method of phosphorus (P) placement and rate on irrigated grain sorghum [Sorghum bicolor (L.) Moench] grown in a ridge‐tillage system on a soil low in available P. This experiment was conducted from 1993 to 1995 on a producer's field near the North Central Kansas Experiment Field at Scandia, Kansas on a Carr sandy loam soil (course, loamy, mixed, calcareous, mesic, Typic Udifuvents). Treatments consisted of fertilizer application methods, surface broadcast, single band starter (5 cm to the side and 5 cm below seed), dual band starter (one band on each side of the row), and knifed in the center of the row middle (38 cm from each adjacent row). Each of these treatments was made at either 22 or 44 kg P₂O₅ ha^‐1, and nitrogen (N) also was included at the rate of 13 kg ha^‐1. Additional treatments were, a combination of 13 kg N and 44 kg P₂O₅ ha^‐1 applied half broadcast and half as a single band starter, a 1:1 N:P₂O₅ ratio (44 kg N and 44 kg P₂O₅ ha^‐1) applied as a single band starter, and a 3:1 ratio (134 kg N and 44 kg P₂O₅ ha^‐1) applied as a single band starter. A no‐P check plot also was included. Broadcast and center‐of‐row middle knife applications were made approximately 1 week before planting. After planting, N was balanced on all plots to give a total of 180 kg ha^‐1. Applied P treatments improved grain yield and nutrient uptake and consistently shortened the time from emergence to mid‐bloom in all 3 years of the experiment. On this low soil test P soil, treatments that subsurface banded P increased grain yield by 1.27 Mg ha^‐1 compared to broadcast treatments. Placing N and P in a single starter band 5 cm to the side and 5 cm below the seed was as effective as placing a band on each side of the row. Knife applying N and P in the center of the row was not as effective as placement beside the row. Single band starter application of N and P in a 1:1 and or 3:1 N:P₂O₅ ratio consistently increased yields and nutrient uptake and shortened the time to mid‐bloom as compared to the single band starter treatment that provided only 13 kg N ha^‐1. Over the 3 years of the study, these 1:1 and 3:1 N:P₂O₅ ratio starters were clearly superior to an other treatments.