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• The Disappearing Nutrient. Gilbert, N. Nature, October 2009, 461:716-718.
  http://www.nature.com/news/2009/091007/full/461716a.html.
  "Phosphate-based fertilizers have helped spur agricultural gains in the past century, but the world may soon run out of them."
• Agricultural Research, Productivity, and Food Prices in the Long Run. Alston, J.M., J.M. Beddow, and P.G. Pardey. Science Magazine, 4 Sept., 2009:325:1209-1210.
  http://www.sciencemag.org/cgi/content/short/325/5945/1209.
• Reaping the Benefits: Science and the Sustainable Intensification of Global Agriculture. A Royal Society Policy document 11/09; Issued: October 2009 RS1608. ISBN: 978-0-85403-784-1.
  Available on http://royalsociety.org/Reapingthebenefits/. "The Royal Society has published the report of a landmark study examining the contribution of the biological sciences to food crop production. The study was conducted by a working group chaired by Sir David Baulcombe FRS. The group included experts on agriculture, international development, conservation biology and plant science."
• Managing Soils for a Warming Earth in a Food-Insecure and Energy-Starved World. Lal, R. 2009. J. Plant Nutr. Soil Sci. 173(1).
  Available on http://www3.interscience.wiley.com/journal/123235291/abstract.

Assessment of Potassium Supply for Corn by Analysis of Plant Parts

Tissue testing of corn (Zea mays L.) ear leaves often is used to diagnose K deficiencies. However, little attention has been given to study how testing of different corn tissues evaluates K supply especially in the optimum to excess range. We evaluated tissue tests for corn based on the K concentration of young plants (V5 to V6), ear leaves at silking, lower stalks at maturity (sections cut from 15 to 35 cm aboveground), and grain. Twenty-eight field trials were conducted in Iowa during 2 yr with fertilizer rates of 0, 56, 112, and 168 kg K ha

Performance of an Optimized Nutrient Management System for Double-Cropped Wheat-Maize Rotations in North-Central China

Over application of N and P and insufficient supply of K are considered primary reasons for restriction of yield improvement in the North China Plain. Optimized nutrient management practices based on soil testing and yield targets have been developed. Other large scale field experiments have indicated that additional improvement for yield and nutrient use benefits is needed. The objective of this study was to evaluate the effects of the optimized nutrient management system on yield, nutrient uptake, nutrient utilization, and profit in the North China provinces of Shanxi, Hebei, Shandong, and Henan. Treatments consisted of a check without fertilizer use (CK); a balanced, optimum nutrient application (OPT); the farmers' practice (FP); and a series of nutrient omission treatments (minus N, P, and K, respectively). The results indicated that the OPT optimized grain yield, nutrient use efficiency, and profitability. Maize (Zea mays L.) yield increased by 12.2% at Shanxi and 18.5% at Hebei, respectively. Inputs of N and P across the wheat (Triticum aestivum L.) and maize system at the four sites was reduced by 13% (266 kg N ha

Potassium Uptake and Partitioning Relative to Dry Matter Accumulation in Cotton Cultivars Differing in Maturity

Dry matter may accumulate faster in fruit of earlier maturing cotton (Gossypium hirsutum L.) cultivars than in later cultivars, requiring more rapid K uptake and/or partitioning to developing bolls. Faster K uptake may require higher K fertility. We examined K uptake and partitioning relative to dry matter accumulation during boll filling of two cultivars contrasting in maturity, under two K fertility regimes at Jackson, TN. Plots fertilized with 56 kg K ha

Rate and Timing of Potassium Fertilization and Fungicide Influence Rice Yield and Stem Rot

Potassium deficient rice (Oryza sativa L.) is susceptible to diseases including stem rot (Sclerotium oryzae Catt.). Knowledge of how to manage K deficiency and the increased disease susceptibility is necessary to reduce rice yield losses. Our objectives were to determine the influence of K rate, application time, and azoxystrobin fungicide on grain yield and stem rot index (SRI) of rice grown on soils with low K availability. Muriate of potash was applied at 0, 56, and 112 kg K ha

Long-Term Fertilizer Experiment Network in China: Crop Yields and Soil Nutrient Trends

Results are summarized for the first 15 yr of an eight-site, long-term experimental network in China designed to assess the sustainability of cropping systems in environments representing 70% of Chinese cropland. Systems were wheat

Growth and Photosynthesis of Salt-Tressed Sunflower (Helianthus annuus) Plants as Affected by Foliar-Applied Different Potassium Salts

In order to assess the effectiveness of foliar-applied potassium (K⁺, 1.25%) using different salts (KCl, KOH, K₂CO₃, KNO₃, KH₂PO₄, and K₂SO₄) in ameliorating the inhibitory effect of salt stress on sunflower plants, a greenhouse experiment was conducted. Sodium chloride (150 mM) was applied through the rooting medium to 18 d-old plants and after 1 week of salt treatment; different K⁺-containing salts were applied twice in 1-week interval as a foliar spray. Salt stress adversely affected the growth, yield components, gas exchange, and water relations, and also caused nutrient imbalance in sunflower plants. However, foliar-applied different sources of potassium improved shoot and root fresh and shoot dry weights, achene yield, 100-achene weight, photosynthetic rate, transpiration rate, stomatal conductance, water-use efficiency, relative water content, and leaf and root K⁺ concentrations of sunflower plants grown under saline conditions. Under nonsaline conditions, improvement in shoot fresh weight, achene yield, 100-achene weight, photosynthetic and transpiration rates, and root Na⁺ concentration was observed due to foliar-applied different K sources. Of the different salts, K₂SO₄, KH₂PO₄, KNO₃, and K₂CO₃ were more effective than KCl and KOH in improving growth and some key physiological processes of sunflower plants.

Effects of Long-Term K Fertilization on Rice Yield and Soil K Status in Reddish Paddy Soil

Effects of Potassium Nutrition on the Fiber Quality among Different Located Sites Cotton Bolls

Potassium (K) plays pivotal role on cotton production and fiber quality. Our present study focused on the effects of K on the quality of fiber. Two cotton varieties Lu18 (L18) and Zhongmian 41 (ZH41), were used and four rates of K fertilizer were applied (K₂O, 0, 60, 180, 300 kg ha^-1) under field condition. The results showed, K application can raise the fiber

Effects of Water Conditions on Available Potassium Contents in Red Soil and Yellow-Cinnamon Soil

Water content plays a crucial role in the soil K content and availability. In this paper, laboratory incubated experiments were carried out to study the effects of different water contents (0, 25% and 40%) and alternative drying-wetting condition on soil available potassium (K) change in red soil and yellow-cinnamon soil at a constant temperature (25

Quantity and Intensity of Potassium and its Exchange Relationship with Calcium in Sunlight Greenhouse Soils

Quantity and intensity of potassium and its exchange with calcium in sunlight greenhouse soils are studied in Guanzhong Plain, Shaanxi. Compared to open field soils, the soils under sunlight greenhouse cultivation have different curves of quantity and intensity of potassium (Q/I). The activity ratios between K⁺, and Ca²⁺ and Mg²⁺ ions of the two greenhouse soils (i.e., manural loess soil and fluvo-aquic soil) are about 14.8 and 6.9 times higher than the corresponding field soils, respectively. The buffer capacities of the greenhouse soils to add K⁺ are lower than those of the field soils. The changes of Gibbs free energy of K⁺, and Ca²⁺ and Mg²⁺ exchange (ΔG) of the greenhouse soils indicate there are excessive accumulation of K⁺ ion and imbalances of K⁺ with Ca²⁺ and Mg²⁺ ions in the soils. As increase of concentrations of K⁺ and Ca²⁺ ions in solution, amounts of adsorbed K⁺ and Ca²⁺ ions by the two soils under both greenhouse and field conditions are increased in a linear pattern, and the adsorption rate of K⁺ ion of the greenhouse soils and adsorption rate of Ca²⁺ ion for both the greenhouse and field soils follows an exponential pattern. When the ratio of K⁺ to Ca²⁺ ions added into soils is 2:1, amounts of adsorbed K⁺ by soils are higher than those of 1:2.5 of K⁺ to Ca²⁺ ions, and Ca²⁺ ion in the greenhouse soils is desorbed. The selectivities of soils to K⁺ to Ca²⁺ ions are changed with the ratios and concentrations of K⁺ to Ca²⁺ ions in the solutions. K⁺ ion is preferential adsorbed when the ratio of K⁺ to Ca²⁺ ions added into soils is 2:1, while, Ca²⁺ ion is preferential adsorbed when the ratio of K⁺ to Ca²⁺ ions is 1:2.5. When over-addition of K⁺ ion into the greenhouse soils occurs, activity of K ion is not increased, and Ca²⁺ ion is largely desorbed. This may affect the soil structure and make the imbalance of nutrients in the greenhouse soils.

Effect of Application of Nitrogen, Phosphorus and Potassium Fertilizers on Yield in Rapeseed (Brassica napus L.) Under the Waterlogging Stress

Two rapeseed (Brassica napus L.) varieties (Zhongshuang No. 10 and Zhongyouza No. 5) were used to study the effects of application of nitrogen (N), phosphorus (P) and potassium (K) fertilizers on yield in rapeseed under the waterlogging stress. The plant was submerged at the seedling stage to mimic the condition of waterlogging. The experiment was replicated two times with "3414" design. The results showed that N, P and K fertilizations significantly affected yield traits in rapeseed under the waterlogging stress. The grey relational analysis showed that N application rate was positively correlated with the number of seed per pod, siliques per plant, primary branches, secondary branches and the length of raceme. The P application rate was positive correlated with the number of siliques per plant and seed per pod. And K application rate was positive correlated with the number of seed per pod, 1000-seed weight and the length of raceme. The results indicated that the ensuring middle level of P and K fertilization, enhanced nitrogen fertilization can significantly increase the yield of rapeseed and the cost value ratio and economic benefits under waterlogging stress. By establishing the fertilizer response equations, the optimum fertilizer applicant of rapeseed under the waterlogging stress were as N 257 kg ha^-1, P₂O₅ 120 kg ha^-1, K₂O 120 kg ha^-1.

Effect of Different Fertilization on Yield and Quality of Fuji Apple

To study effects of different N, P and K fertilization on quality and yield of Fuji apple in order to provide the theoretical foundation for high yield and quality of apple production in the Weibei tableland, A 5 year field experiment from 2004 to 2008 was conducted. The results showed that the apple yields are increased by 12.62% to 48.57% under the different fertilization, and the order of increase rates by the elements is N>K≥P. The effect of application of N fertilizer combined with P and K fertilizers is the best, the ratio of apple diameters which are bigger than 75 mm is increased from 53.7% in 2004 to 81.2% in 2008, and the ratio of sugar/acid is increased from 37.1 to 39.9. However, for the NP, PK and NK treatments, the ratio of sugar/acid, Vc and hardness are all decreased, especially for the NP treatment, the ratio of sugar/acid and Vc are decreased by 36.3% and 15.6% respectively. Application of N, P combined with K fertilizer can improve the apple yield and quality.

Comparison of Potassium Absorption and utilization for Different Cotton Varieties

Potassium absorption and utilization for different cotton varieties were studied based on the screening experiment of seedling stage. The varieties are potassium-efficiency genotypes, Xinluzao 6, Xinluzhong 15, and Xinhai 16, and potassium-inefficiency genotypes, Xinluzao 10 and Shi K7. The results show that there are significant differences between potassium content, potassium accumulation and biomass yield of the different cotton genotypes under the two potassium conditions. The Xinluzhong 15 is the best genotype in potassium content, potassium accumulation and biomass yield without potassium application. The qualities of potassium content, potassium accumulation and biomass yield are 1.17 times, 1.47 times and 1.25 times of those of Shi K7. Values of the potassium utilization index are different in different cotton genotypes especially under the condition of potassium application. The potassium utilization index of Xinluzhong 15 under the condition of potassium application is 1.40 times, 1.31 times and 1.34 times of that of Shi K7 in 80 d, 120 d and 140 d.

Advance of Rice Fertilizer-Nitrogen Use Efficiency

Fertilizers can become a source of pollution when they are used in excess. Reducing application rate of fertilizer-nitrogen use and increasing efficiency of fertilizer-nitrogen use for irrigate rice is an important task for the agricultural scientists. In this paper, research advances on relationship between efficiency of fertilizer-nitrogen use and the application method of fertilizer-nitrogen use, rice genotype differences, root growth, matter accumulation, physiological metabolism, plant characteristics were reviewed. Rice variety with stronger root system was in favor of raising the absorptive capacity of soil nitrogen; Stronger tillering ability, higher grain-leaf ratio at full heading stage, dry matter accumulation after heading stage, seed-setting rate, grain weight, yield and harvest index of cultivars resulted in higher nitrogen use efficiency. Its physiology characteristics were characterized by higher activities of nitrate reductase, glutamate synthase and the activity of RuBP carboxylase. Ways of increasing fertilizer-nitrogen use efficiency (i.e. balancing between N and P, K, improving method of fertilizer-nitrogen and water management, and applying accurately fertilizer-nitrogen), were also discussed. At last, research hotspots regarding N losses reduction and N use efficiency enhancement were put forward.

Efficiency of Potash Fertilizer in Rice-Wheat Cropping System in Northwestern Region of Bangladesh

Research trials and farmers' field demonstrations were conducted to study the effect of potassium fertilizer on the performance of rice and wheat under rice-wheat cropping pattern. Six treatments with varying doses of inorganic K including the recycling of crop residues in research trials and three K treatments in farmers' field demonstration were evaluated. Use of potassium @ 66 kg ha^-1 appeared to be sufficient and economically most viable to produce optimum grain yield in both T. Aman rice and wheat crops. Incorporation of crop residue @ 4.5 t ha^-1 (oven dry basis) substantially increased the rice and wheat yield which was comparable to that of 33 kg K ha^-1 and farmer's K dose applied as inorganic fertilizer. Potassium fertilization increased the T. Aman rice grain up to 30% and wheat grain up to 53% in research trial and grain yield of wheat by 86% and T. Aman rice by 25% in farmers' field demonstration over K control plot. Application of K fertilizer minimized the K mining and the magnitude of K depletion gradually decreased with increasing K level. Incorporation of crop residues substantially contributed to build up K reserve in soil. The additional income earned resulting from K fertilization was much higher in wheat than in rice.

Integrated Plant Nutrient Supply and Management Strategies for Enhancing Soil Quality, Nutrient Use Efficiency and Crop Productivity

Improving and maintaining soil quality for enhancing and sustaining agricultural production is of utmost importance for India's food and nutritional security. Though India has made a record production of about 230 million tonnes of food grains in 2007-08, it will need to produce about 320 million tonnes of food grains by 2025 if the trend in rising population persists. This challenge can be met by greater and more efficient use of fertilisers and organic sources of plant nutrients. The results from several long-term fertiliser experiments conducted in different agro-ecological regions involving diversified cropping systems and soil types have shown that imbalance fertiliser use particularly N alone had a deleterious effect on soil productivity and health and the damaging effects in the absence of P and K fertilisers varied in the order. Alfisols>Vertisols>Inceptisols>Mollisols. In a period of less than ten years, crop productivity in N alone plots came to almost zero in Alfisols. Integrating organic manure (FYM @ 10-15 Mg ha^-1) with 100% recommended NPK fertiliser doses not only sustained high productivity but also maintained fertility in most of the intensive cropping systems and soil types. The results further revealed that soil type was one of the most important factor affecting fertiliser use efficiency and crop yields. Therefore, sustained efforts are needed to improve and maintain this most important natural resource base (soil) through judicious integration of fertilisers, organic and green manures, crop residues and biofertilisers so that it nourishes intensive cropping without being irreversibly damaged in the process. Important soil chemical parameters (soil organic matter, pH, electrical conductivity, available major and micronutrients), physical parameters (texture, depth of soil, infiltration, bulk density, water holding capacity), and biological parameters (microbial biomass, C and N, potentially mineralizable N, soil respiration, soil biodiversity) interact in a complex way to provide soil important functions thereby affecting nutrient use efficiency and crop productivity. The balanced fertilization along with manures improves the soil aggregation as well as biological activity of soil and maintains soil quality and sustainability of productivity. The soil quality index calculated for the different fertiliser treatments decreased in the following order: 0.838 (100% NPK + FYM) >0.777 (150% NPK) >0.729 (100% NPK) >0.637 (100% NP)/0.637 (50% NPK)/0.623 (reference) >0.591 (100% N) >0.552 (control).

Nutrient Management Strategies in Participatory Watersheds in Semi Arid Tropical India

Watershed based nutrient management options in different states (Andhra Pradesh, Madhya Pradesh, Karnataka, Rajasthan, Gujarat, Haryana and Tamil Nadu) were evaluated on farmer's fields based on initial soil characterization. Besides N and P, several other secondary and micronutrients such as S, Zn and B were found deficient in farmer