K in the Literature

High Potassium Aggravates the Oxidative Stress Inducedy by Magnesium Deflciency in Rice Leaves

Magnesium (Mg) deficiency in plant affects photosynthesis and many other metabolic processes. Rice (Oryza sativa L. cv. 'Wuyunjing 7') plants were grown in hydroponics culture at three Mg and two potassium (K) levels under greenhouse conditions to examine the induction of oxidative stress and consequent antioxidant responses in rice leaves due to Mg deficiency. At low Mg (0.2 mmol L^-1 Mg supply for two weeks after transplanting) and high K (6 mmol L^-1) for 21 days, the rice plants showed severe Mg deficiency and a significant decreases in the dry matter production. The Mg deficiency in leaves decreased chlorophyll concentrations, photosynthetic activity, and soluble protein, but significantly increased the concentrations of soluble sugars and malondialdehyde (MDA) and the activities of superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6) and peroxidase (POD, EC 1.11.1.7). In addition, Mg concentrations in the leaves and in the shoot biomass were negatively related to the activities of the three antioxidative enzymes and the concentration of MDA in leaves. There were very significant interactive effects between Mg and K supplied in the culture solution on shoot biomass yield, chlorophyll content, photosynthesis rate, the activities of SOD, CAT and POD, and MDA content in the leaves of rice. It is suggested that the high K level in the nutrient solution aggravated the effect of low Mg supply-induced Mg deficiency and created the oxidative damage in rice plants.

Ability of Sorption-Desorption Experiments to Predict Potassium Leaching from Calcareous Soils

When potassium (K⁺) fertilizers are applied to the soil, K⁺ is subject to displacement through the soil profile. Leaching can play an important role in agricultural K⁺ losses that can decrease groundwater quality. To avoid over fertilization, estimation of K⁺ leaching from soil is important. The ability of the soils to retain K⁺ against leaching varies according to the adsorption coefficient of the soils. The aim of this study was to relate the K⁺ leaching from a wide range of calcareous soils to the values obtained from a sorption-desorption experiment. The soil columns were leached with 10 mM CaCl₂ solution and the leachate was analyzed for K⁺. The breakthrough curves for K⁺ were different, and the amounts of K⁺ leached varied considerably between different soils. In these calcareous soils where crops are irrigated with water containing significant concentrations of Ca²⁺ and other cations, large amounts of K⁺ will be leached. Cumulative K⁺ leached after five pore volumes leaching with 10 mM CaCl₂ was significantly (r = 0.776, p < 0.01) related to the equilibrium K⁺ concentration. The results of this study enabled us in many cases to estimate the K⁺ leaching from soil without conducting column experiments, minimizing the laborotary work.

Influence of Phosphorus, Nitrogen, and Potassium Chloride Placement and Rate on Durum Wheat Yield and Quality

Information regarding the impact of P and KCl rate and placement in conjunction with N rate on durum wheat (Triticum turgidumL. var. durum) is limited in the Great Plains. Our objectives were to determine the effects of N, P, and KCl fertilizer rate and P and KCl placement on grain yield and quality of durum wheat grown on low P soils. Nine combinations of N and P fertilizer and five combinations of N, P, and KCl applied with the seed and in a side band, were compared over 3 yr at Indian Head SK, in fields with soil P levels <9 kg ha

Impact of Different Nitrogen Fertilizers and an Additional Sulfur Supply on Grain Yield, Quality, and the Potential of Acrylamide Formation in Winter Wheat

The amino acid asparagine (Asn) plays a key role in acrylamide (AA) formation in strongly heated cereal foodstuffs. The influence of different nitrogen (N) fertilizers (calcium ammonium nitrate, CAN; urea ammonium sulfate solution, UAS, applied according to the CULTAN method; urea; urea ammonium nitrate, UAN; ammonium nitrate sulfate containing the nitrification inhibitor 3,4-dimethyl pyrazole phosphate, Entec 26^®; and a combination of liquid manure and CAN) at a nitrogen level of 180 kg N ha^-1 and an additional sulfur (S) supply on grain yield, quality, Asn concentration, and the potential of AA formation of winter wheat were studied in a 2-year field experiment. Grain yields varied between 61 und 104 dt ha^-1 dry matter depending on cultivar (cv), fertilization, and year. Quality demands concerning crude protein concentration and sedimentation value were reached when CAN, CAN+S, urea, or a combination of liquid manure and CAN were applied. Asparagine concentrations in flours varied from 2.6 to 13.6 mg per 100 g flour dry matter depending on cultivar, fertilization, and year. In both years, a close nonlinear correlation between crude protein concentration and the concentration of free Asn with r²₂₀₀₄ = 0.93 and r²₂₀₀₅ = 0.94 was observed. Nitrogen fertilizers leading to high crude protein concentrations caused significantly increased Asn concentrations. In both years, a correlation between the concentration of free Asn and the potential of AA formation with r²₂₀₀₄= 0.72 and r²₂₀₀₅= 0.84 was found. The application of S (CAN compared to CAN+S) had no beneficial effect on the Asn concentration and the potential of AA formation, most likely because S concentration in grains was sufficient even without additional S supply.