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1.
Abstract

Minimum sufficiency levels of hull and seed Ca for maximum yield and grade of runner or Virginia type peanuts (Arachis hypogaea L.) have not been established and there is limited information on single and combined effects of limestone and gypsum on production and quality of peanuts. Field experiments were conducted on runner and Virginia type peanuts to study single and combined effects of limestone and gypsum on yield and grade, and to attempt to establish minimum sufficiency levels of hull and seed Ca for maximum yield and grade of each type. Gypsum treatments, O, low, medium, and high rates, were superimposed on residual limestone rates on three sites with ‘Florunner’ (runner type) and on one site with ‘NC‐7’ (Virginia type) peanuts. Yield and grade of Florunner peanuts were not increased by limestone or gypsum treatments on any site even though soil Ca concentrations (Mehlich 1) ranged from 152 to 200 mg/kg among the sites. These levels were lower than the Georgia recommended minimum sufficiency value of 250 mg/kg. However, yield and grade of ‘NC‐7’ peanuts were increased by limestone or gypsum, but maximum yield occurred only where gypsum was applied even with soil Ca levels of 682 mg/kg. The minimum hull Ca level of 1.2 g/kg and seed Ca of 0.42 g/kg were sufficient for Florunner peanuts since yields and quality were not increased by limestone or gypsum application. Maximim yield and grade were achieved with Florunner at leaf, hull, and seed Ca concentrations of 13.2, 1.2, and 0.42 g/kg as compared with 26.0, 1.9, and 0.58 g/kg for NC‐7, respectively. These data show that NC‐7 has a higher Ca requirement than Florunner.  相似文献   

2.
受钙影响的花生生殖生长及种子素质研究   总被引：5，自引：1，他引：5  
采用砂培试验结合电子探针等分析方法研究受钙影响的花生生殖生长及种子素质。结果表明 ,低钙导致花生花粉外观变形 ,花粉壁松弛 ,淀粉粒小而稀少 ;电子探针下花生壁K峰升高 ,Ca、P、S和Si峰降低 ,从而影响花粉活力。在一定供钙范围 ,花生总花数、可育花数及产量随供钙增加而增加 ,影响总花数临界供钙水平为 0.6cmol(+) /kg ;影响可育花数及产量的临界供钙水平平均为 1.2 (+) /kg。花生种子钙含量与供钙水平呈显著直线相关 ,其直接影响种子发芽率和出苗率。 95%以上的花生发芽率和出苗率分别要求种子钙含量不低于 235和 278mg/kg  相似文献   

3.
Abstract

Direct fertilization of peanuts (Arachis hypogaeaL.) with P and K has generally shown few yield responses, resulting in only limited information concerning critical soil‐test levels of P and K. The purpose of the experiments in this report was to determine the critical soil‐test levels of P and K for runner peanuts using the double‐acid extraction procedure. Fertilizer experiments were conducted on farmers’ fields from 1973 to 1986. Site selection was based on soil test data that indicated “medium”; or “low”; levels of available P or K but “high”; in Ca and Mg. Phosphorus and potassium were applied together at all sites at rates of 20 and 74 kg/ha, respectively, as concentrated superphosphate and potassium chloride.

There were yield increases to fertilizer in 6 of the 39 experiments. Soil‐test P for these six ranged between 4 and 53 kg/ha; soil‐test K ranged between 10 and 31 kg/ha. Delineating the yield effect into their P and K components with the aid of multiple regressions of yield on soil test values showed that yield increases were due to the K component of the fertilizer. The critical soil‐test K value was calculated to be 37 kg/ha. Sound mature kernels (SMK) were generally unaffected by fertilizer.  相似文献   

4.
Abstract

Adequate availability of calcium (Ca) in the upper 7–10 cm of soil is extremely important for pod development and therefore for production of quality peanut (Arachis hypogaea L.). Supplemental Ca is usually applied as gypsum, however, availability of Ca may depend on the type of gypsum. The objective of a laboratory study was to evaluate recovery of Ca in Mehlich I, 0.01 M NaNO3 and deionized water extractants from seven gypsum materials which varied physically from fine and coarse powders to crystals, granules and pellets. Overall, recovery of Ca was much greater in Mehlich I (89.5–99.6% of total Ca) than in either 0.01 M NaNO3 (81.0–98.4%) or deionized water (78.7–97.5%). However, for 3 sources, recovery of Ca was very similar in NaNO3 solution and deionized water.

Field experiments were conducted on Lakeland sand (Mehlich I Ca = 127 kg/ha, 0–15 cm) and Tifton loamy sand (Mehlich I Ca = 665 kg/ha) soils to study the effects of the gypsum materials on Florunner peanut grade and yield. Effects of gypsum treatments on Mehlich I‐ and 0.01 M NaNO3‐extractable soil Ca were also evaluated during peanut pod development. On the Lakeland soil, Mehlich I Ca increased from 127 to a range of 420–737 kg/ha following application of gypsum depending on the type of gypsum material. Percent sound mature kernels were significantly greater where gypsum was applied than in the control treatment, regardless of source. Total sound mature kernel yield and gross return were greatest for the more soluble sources. The yield vs. soil test Ca relationship 90 d after planting revealed that yield response was very minimal if soil Ca was greater than 290 and 85 kg/ha of Mehlich I and 0,01 M NaNO3‐extractable Ca, respectively. Application of gypsum to the Tifton soil, regardless of type of material, had no significant effect on yield, grade or gross return because Mehlich I extractable Ca in the control treatment was well over 560 kg/ha; the critical soil test Ca for runner peanut according to the current Georgia soil test recommendation.  相似文献   

5.
Abstract

An adequate supply of available Ca in the soil solution of the pegging zone during fruit development is required for production of high yields of high quality peanuts (Arachis hypogaea L.). On low Ca soils, application of gypsum during early bloom is recommended in order to ascertain adequate availability of Ca. Reaction of gypsum in soils under leaching conditions vary considerably and play an important role in fruit development and yield of peanuts. A laboratory study was conducted in leaching soil columns to investigate the effects of one gypsum amendment on leaching of Ca, K, Mg, and SO4 to a depth of 8 cm (fruiting zone of peanut). Six soils of varying physical and chemical properties representative of major peanut growing soils in Georgia were utilized. Following leaching with 15 cm water through gypsum‐amended soil columns, 50% to 56% and 74% to 77% of applied Ca and SO4, respectively, were leached below 8 cm in the sandy‐Carnegie, Dothan, Fuquay and Tifton soils. The respective values for the sandy clay loam‐Greenville and Faceville soils were 28% to 36% and 58% to 69%. Lower initial Ca status and greater leaching of Ca from the applied gypsum in the sandy soils as compared to sandy clay loam soils suggest greater beneficial effects of supplemental gypsum application for peanut production in the former soils than in the latter soils. Leaching of K or Mg (as percentage of Mehlich 1 extractable K or Mg) in gypsum‐amended treatment was considerably greater in sandy soils than that in the sandy clay loam soils. In view of the reported adverse effects of high concentrations of soil K and Mg in the fruiting zone on the yield and quality of peanuts, greater leaching of K and Mg from the fruiting zone in gypsum amended sandy soils enable them to maintain a favorable cation balance for the production of high yields of quality peanuts.  相似文献   

6.
High zinc (Zn) concentration of seeds has beneficial effects both on seed vigor and human nutrition. This study investigated the effect of Zn biofortification on growth of young durum wheat (Triticum durum cv. Yelken) seedlings under varied Zn and water supply. The seeds differing in Zn concentrations were obtained by spraying ZnSO4 to durum wheat plants at different rates under field conditions. Three groups of seeds were obtained with the following Zn concentrations: 9, 20, and 50 mg Zn kg?1. The seeds differing in Zn were tested for germination rate, seedling height, shoot dry matter production, and shoot Zn concentration under limited and well irrigated conditions in a Zn‐deficient soil with and without Zn application. In an additional experiment carried out in solution culture, root and shoot growth and superoxide dismutase activity (SOD) of seedlings were studied under low and adequate Zn supply. Low seed Zn concentration resulted in significant decreases in seedling height both in Zn‐deficient and sufficient soil, but more clearly under water‐limited soil condition. Decrease in seed germination due to low seed Zn was also more evident under limited water supply. Increasing seed Zn concentration significantly restored impairments in seedling development. Drought‐induced decrease in seedling growth at a given seed Zn concentration was much higher when soil was Zn‐deficient. Increasing seed Zn concentration also significantly improved SOD activity in seedlings grown under low Zn supply, but not under adequate Zn supply. The results suggest that using Zn‐biofortified seeds assures better seed vigor and seedling growth, particularly when Zn and water are limited in the growth medium. The role of a higher antioxidative potential (i.e., higher SOD activity) is discussed as a possible major factor in better germination and development of seedlings resulting from Zn‐biofortified seeds.  相似文献   

7.
The present study evaluated effects of seed zinc (Zn) priming at concentrations from 0 to 25 mM ZnSO4 on seedling vigor and viability in rice (Oryza sativa L.). Zinc priming substantially increased Zn concentration in the husk, but not in brown rice. The movement of primed Zn from the husk into the inner layers of rice seed during germination was suggested by Zn concentration declining in the husk coinciding with the increase in brown rice over time (r = –0.62; p < 1%), which did not happen in unprimed seed. Zinc priming significantly enhanced seedling growth and development up to 5 mM. Germination rate, root number, and dry weight were much higher than in unprimed seed, but higher Zn concentrations (10 and 25 mM) depressed seedling vigor. Priming rice seed with 2.5 mM Zn also improved the germination rate of rice in a Zn‐deficient soil, with or without soil Zn application. The results confirm that priming rice seed with Zn can improve germination and seedling vigor and for the first time show how Zn requirement of germinating rice seed and seedlings can be met by the prime Zn accumulated in the husk.  相似文献   

8.
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.  相似文献   

9.
The effect of 2,4,5-trichlorophenoxy acetic acid (2,4,5-T) on the germination and seedling vigor of different crop seeds was tested. Seeds of rice, maize, sorghum, finger millet, and horse gram were comparatively more tolerant to the chemical with no marked effect up to a concentration of 200 mg 2,4,5-T L(-)(1) as tested by the filter paper method. Tomato and brinjal (egg plant) were highly susceptible. Even at 5 and 10 mg 2,4,5-T L(-)(1), marked reduction in the germination and seedling vigor of tomato and egg plant, respectively, was observed. At 20 and 30 mg L(-)(1), the germination of tomato and egg plant seeds, respectively, were completely inhibited on filter paper, whereas the inhibitory concentrations in soil was 40 mg 2,4,5-T kg(-)(1) soil. Several abnormalities were observed in the chemically affected seedlings. Protease activity of the seeds germinating in the presence of the chemical was drastically reduced. Bioremediation of the chemically contaminated soil with Burkholderia cepacia AC1100, by inoculation of the soil 7 days before sowing the seeds, completely protected the seeds, resulting in normal germination and an improved seedling vigor.  相似文献   

10.
Abstract

Field and greenhouse studies were conducted in Idaho in 1985 to document the maximum levels of a salt fluxing residue (slag) material that can be safely applied to agricultural soils without reducing spring wheat (Triticum aestivum) growth. The slag material, which contains significant quantities of Mg and K, was applied to Mission (coarse‐silty, mixed, frigid Andic Fragiochrepts) and Palouse (fine‐silty, mixed, mesic Pachic Ultic Haploxerolls) silt loam soils at rates ranging from 0 to 40,000 kg/ha. Parameters evaluated included: (1) germination, (2) plant vigor, (3) yield, and (4) soil and plant tissue K, Ca and Mg.

Under field conditions slag application rates of 4,000 and 8,000 kg/ha reduced wheat stands and vigor; however, yields were not adversely affected when compared with the control. Application rates in excess of 8,000 kg/ha resulted in reduced germination, plant vigor, and yield and are consequently not recommended. Greenhouse studies provided further evidence to substantiate the field results.  相似文献   

11.
Abstract

Bragg soybeans [Glycine max. (L. ) Merill] were grown under field conditions near Sanford, Florida on a tile‐drained Immokalee fine sand (sandy, siliceous, hyperthermic Arenic Haplaquod). The objectives were: 1) to assess the K and P fertilizer requirements of soybeans grown in central Florida 2) to correlate soil and tissue nutritional levels with extractable soil nutrients and 3) to assess the influence of K application time on yield.

Experimental treatments were four K rates (0, 50, 100, and 200 kg K/ha), three P rates (0, 25, and 50 kg P/ha), and two sidedress K rates (0 and 50 kg K/ha) at early bloom. Treatments were arranged in a randomized complete block design and replicated four times.

Yield increased with each increase in applied K. Statistical maximum yield was obtained on plots which contained 103 ppm double‐acid extractable K during the pod‐filling stage of growth. Tissue K at early bloom exceeded 2.85% at maximum statistical yield. Potassium applied broadcast at early bloom did not significantly influence yield.

This soil contained approximately 390 ppm double‐acid extractable P prior to P application. No significant yield response to applied P was observed, indicating that the original extractable P content of the soil was adequate for the yield level obtained.

The quadratic regression of the ratio equivalents of double‐acid extractable K:Ca + Mg on the same ratio for the plant tissue is highly significant. This expression was a good predictor of tissue accumulation of these nutrients in that the coefficient for determination was 0.68.  相似文献   

12.
Interest in developing crop varieties with low grain phosphorus (P) in order to minimize the removal of P from fields in harvested grain has been limited due to the view that a low‐P grain trait may impair subsequent seedling vigor. This perception is based on relatively few studies, which typically investigated seedling growth on infertile soils, and used seed that may have differed in attributes other than P concentration. To investigate whether these anomalies cast sufficient doubt to warrant renewed research in this field, we compared the growth of rice seedlings from seed low in P obtained from P‐starved plants (P‐starved seed) vs. high‐P seeds (obtained from P‐fertilized plants) in P‐deficient and P‐replete soils. While plants from high‐P seed were superior in the P‐deficient soil, plants grown from P‐starved seed overcame an initial lull in early vigor to obtain similar biomass at maturity as plants grown from high‐P seed. Subsequent experiments were undertaken using high‐P seed vs. seed low in P from a range of rice genotypes that was not obtained from P‐stressed plants (low‐P seed): There was no reduction in seedling vigor or biomass and grain yields at maturity of plants from low‐P seeds in low‐P soil compared to plants from high‐P seed, though responses were genotype‐specific. The results suggest that multiple factors can confound the results of seed P × seedling vigor studies, and that a renewed research effort to define the minimum P levels in seeds required for adequate seedling growth across a range of environments is warranted.  相似文献   

13.
Abstract

Mehlich 1‐Ca is used as an index to predict the Ca requirement for peanut (Arachis hypogaea L.) fruit development in major peanut growing states. Recently, some concern has been raised about the inadequacy of Mehlich 1 extractable Ca for that purpose. Possible use of alternative extractants for soil Ca has been suggested. In this study, relationships among Mehlich 1, 0.2 M NH4Cl and 0.01 M NaNO3 extractable Ca were examined in several Coastal Plain soils to which gypsum or lime had been applied. Variability in extractable Ca was much greater following lime treatment than following gypsum treatment. In Bonifay soil, the quantity of Ca extractable by the three extractants was similar in a gypsum treatment, but in a lime treatment (at an application rate equivalent to the gypsum treatment) Mehlich 1‐Ca was 2 and 5‐fold greater than NH4Cl‐ and NaNO3‐Ca, respectively. In Greenville soil, Mehlich 1‐Ca was 3 to 4‐fold greater than NaNO3‐Ca regardless of gypsum or lime amendment.

For soil samples from a field experiment on Lakeland sand, where lime or gypsum was applied prior to planting, Mehlich 1‐Ca was 7.5 and 2.2‐fold greater than NaNO3‐Ca for the lime and gypsum treatments, respectively. Greater variability in Mehlich 1‐Ca in lime than in gypsum treatments was due to possible inclusion of undissolved limestone in the soil samples, resulting in overestimation of Ca available for peanut fruits. Mehlich 1‐Ca appears to be an adequate index of soil Ca for prediction of supplemental Ca requirement for peanut if lime has not been applied or has been applied well in advance of planting, thus minimizing the inclusion of undissolved limestone with the soil sample taken from the fruiting zone (0–8 cm depth) 10–14 d after planting.  相似文献   

14.
Abstract

Management practices during seed development are crucial for boosting seed quality and establishment. This study determined the interactive effect of soil fertility and maturity stage on maize seed quality. The cultivar SC701 were harvested at milk, dent, and physiological maturity stages and dried to <12% moisture content. Field trials were split plots replicated four times. Seed quality was evaluated using standard germination test, vigor indices and electrical conductivity test. Highly significant interactions (p?相似文献   

15.
Abstract

Carrots were grown on a Joel sand amended with several levels of applied gypsum‐treated bauxite residue (RMG) up to 240 t‐ha‐1, to test whether the residue reduces phosphorus (P) leaching when applied to the soil. Phosphorus sorption, measured using the Modified Phosphorus Retention Index (PRIM), was initially 30 at 2401 RMG ha‐1 due to a combination of iron and aluminum oxides, calcium carbonate (CaCO3), and soluble calcium (Ca). Four months after harvest, PRIM had decreased to 10 at 240 t RMG ha‐1 (PRIM of 4 on unamended soil) due to the leaching of soluble Ca. Retention of fertilizer (P) (0–15 cm) at 160 kg P ha‐1 increased from 34% on unamended soil to approximately 100% at 60 and 240 t RMG ha‐1 one month after fertilizer application. Bicarbonate‐extractable P at harvest reached 60 to 65 mg‐kg‐1 at 120 and 240 t RMG ha‐1 when 346 kg P ha‐1 was applied, whereas on unamended soil, levels did not exceed 30 mg‐kg‐1, regardless of the level of applied fertilizer. Plant uptake of P was reduced due to the precipitation of calcium phosphate compounds, although final yield was unaffected possibly because of slow re‐release of P from precipitated calcium phosphate compounds. Red mud was difficult to wash off carrots grown on soil amended with 2401 RMG ha‐1. The use of RMG may have a place in the management of horticultural crops in areas at risk from P pollution. However, more work is needed to investigate ‘aged’ RMG‐amended sites since the P retention in this experiment was affected by soluble Ca and also by post‐planting P applications.  相似文献   

16.
Effects of Ca (Ca2+) level on the response of germination and seedling growth of Salvadora persica Linn. (Salvadoraceae) to sodium chloride (NaCl) salinity in soil were investigated. Salinity significantly retarded the seed germination and seedling growth, but the injurious effects of NaCl on seed germination were ameliorated and seedling growth was restored with Ca supply at the critical level to salinized soil. Calcium supply above the critical level further retarded the seed germination and seedling growth because of the increased soil salinity. Salt stress reduced nitrogen, phosphorus, potassium, and Ca content in plant tissues, but these nutrients were restored by addition of Ca at the critical level to saline soil. The opposite was true for sodium (Na+). The results are discussed in terms of the beneficial effects of Ca for plant growth under saline conditions.  相似文献   

17.
Soybean is one of the most important legume crops in the world. Two greenhouse experiments were conducted to determine the influence of liming and gypsum application on yield and yield components of soybean and changes in soil chemical properties of an Oxisol. Lime rates used were 0, 0.71, 1.42, 2.14, 2.85, and 4.28 g kg?1 soil. Gypsum rates applied were 0, 0.28, 0.57, 1.14, 1.71, and 2.28 g kg?1 soil. Lime as well as gypsum significantly increased grain yield in a quadratic fashion. Maximum grain yield was achieved with the application of 1.57 g lime per kg soil, whereas the gypsum requirement for maximum grain yield was 1.43 g per kg of soil. Lime significantly improved soil pH, exchangeable soil calcium (Ca) and magnesium (Mg) contents, base saturation, and effective cation exchange capacity (ECEC). However, lime application significantly decreased total acidity [hydrogen (H) + aluminum (Al)], zinc (Zn), and iron (Fe) contents of the soil. The decrease in these soil properties was associated with increase in soil pH. Gypsum application significantly increased exchangeable soil Ca, base saturation, and ECEC. However, gypsum did not change pH and total acidity (H + Al) significantly. Adequate soil acidity indices established for maximum grain yield with the application of lime were pH 5.5, Ca 1.8 cmolc kg?1, Mg 0.66 cmolc kg?1, base saturation 53%, Ca saturation 35%, and Mg saturation 13%. Soybean plants tolerated acidity (H + Al) up to 2.26 cmolc kg?1 soil. In the case of gypsum, maximum grain yield was obtained at exchangeable Ca content of 2.12 cmolc kg?1, base saturation of 56%, and Ca saturation of 41%.  相似文献   

18.
Whether due to the genotype or the environment of the mother plant, the nutrient content of seeds vary over a wide range; the amount of the nutrient contributes greatly to seedling vigor, especially on deficient soils and may result in major differences in grain yield. This effect has important implications for breeding programs. This paper examines the impact of seed manganese (Mn) on screening of durum wheats for tolerance to Mn‐deficient soils. Seed stocks with a range of Mn contents (0.4–2.4 μg seed‐1) were produced, and the effect on expression of Mn efficiency measured as either relative yield or shoot Mn content for two durum wheat (Triticum turgidum L. var. durum) genotypes differing in Mn efficiency. Both genotypes responded to seed Mn content in terms of enhanced root and shoot growth; there was no genotype by seed Mn interaction, so Mn provided in seed was utilized additively by both Mn‐efficient and Mn‐inefficient genotypes. Manganese efficiency, measured as relative yield, was a function of seed Mn content and varied from 40 to 70% in Hazar and 58 to 90% in Stojocri 2, in the same assay using seed of variable Mn content. From the response curves of yield vs. soil Mn added, the Mn required for 90% relative yield was determined for each level of seed Mn content. Seed Mn was regressed against the soil added Mn needed to obtain 90% of maximal growth at each level of seed Mn content (a total of 8 levels) for each of two genotypes. There was an inverse linear relationship between the amount of soil Mn and seed Mn needed for each genotype. Using the Mn‐efficient genotype with high seed Mn content, the soil Mn needed to obtain 90% growth was nil, while inefficient genotypes with low Mn content required 75 mg Mn kg‐1 soil to produce the same relative yield. This relationship can be used to adjust the levels of soil applied Mn to be used in a pot bioassay when seeds have a certain Mn content, so as to maintain the screening at an optimal overall level of Mn stress.  相似文献   

19.
Optimal potassium (K) fertilization is beneficial for oilseed‐rape (Brassica napus L.) yield and quality. However, the discrepancy between the high K demand of winter oilseed rape and low soil fertility and insufficient potassium input has limited the sustainable development of oilseed‐rape production. A series of on‐farm experiments in the key winter oilseed‐rape domains of China was conducted from 2004 to 2010 to evaluate K‐fertilizer management for winter oilseed rape. Currently, the average NH4OAc‐extractable K content in the 0–20 cm soil layer is 89.1 mg kg–1 indicative of “slight deficiency”. In addition, farmers in China usually fail to use sufficient K fertilizer in oilseed‐rape production, the average mineral‐potassium‐fertilizer input in 2010 being only 35 kg K ha–1, far lower than the recommended rate of potassium for winter oilseed rape. Adequate potassium fertilization significantly raises seed yield. The average yield‐increase rate for the major production regions due to K‐fertilizer application was 18.5%, and the average K fertilizer–use efficiency 36.1%. Based on the negative correlation between yield response to potassium fertilization and available soil K content, a soil‐K‐test index was established for winter oilseed rape with a threshold value for NH4OAc‐extractable soil K of 135 mg kg–1. When available soil K‐content is below this threshold value, more K fertilizer should be applied to achieve high seed yield and to increase soil fertility. The major challenge for K‐fertilizer management in winter oilseed‐rape production in China will be to guide farmers in the different regions in making reasonable use of K fertilizer through soil K‐testing technology in order to maintain both seed yield and soil fertility.  相似文献   

20.
Abstract

Zinc toxicity of peanuts (Arachis hypogaea L.), resulting from excessive amounts of Zn applied to previous crops, has been observed for many years in a limited number of peanut fields in Georgia. A tentative critical value of 12 mg/kg of Mehlich No.1 extractable soil Zn has been reported, but soil pH should be considered in establishing a more precise critical value since availability of soil Zn is affected greatly by soil acidity. A 3‐year study was conducted on a Tifton loamy sand (thermic, Plinthic Paleudults) to evaluate the relationship between soil pH and soil Zn on concentration of Zn in peanut leaves. Factorial treatments were 0, residual, medium, and high rates of Zn and soil pH levels near 5.5, 5.9, 6.2, and 6.8. Pod yields were not affected by treatments and Zn toxicity was not observed. Leaf Zn was affected more by soil pH than by soil Zn, but correlation coefficients were highest where both soil pH and soil Zn were included in the determination. A regression equation, based on soil pH and soil Zn, showed that an increase in soil Zn from 1.0 to 10.0 mg/kg increased leaf Zn 202 mg/kg at soil pH 4.6 and only 9 mg/kg at pH 6.6. Data from growers’ fields, in which samples were collected from eight healthy and toxic areas, indicated that a leaf Ca:Zn ratio of 50 or less was required for Zn toxicity of peanuts rather than high concentrations of leaf Zn per se.  相似文献   

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