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• Agricultural Research, Productivity, and Food Prices in the Long Run. Alston, J.M., J.M. Beddow, and P.G. Pardey. Science 4 September 2009: 325(5945):1209-1210.
  DOI: 10.1126/science.1170451. www.sciencemag.org
• Can Organic Agriculture Feed the World? Goulding, K.W.T., and A.J. Trewava. AgBio View. 23 June 2009. www.agbioworld.org
• Digital Soil Map of the World. Sanchez et al. 2009. Science 7 August 2009:325(5941):680-681.
  DOI: 10.1126/science.1175084. www.sciencemag.org 
• Fertilizer Subsidies in Africa: Are Vouchers the Answer? Minot, N., and T. Benson. 2009. IFPRI Issue Brief 60. July 2009. www.ifpri.org
• Nutrient Imbalances in Agricultural Development. Vitousek et al. Science 19 June 2009: 324(5934):1519-1520.
  DOI: 10.1126/science.1170261. www.sciencemag.org
• Nutritional Quality of Organic Foods: A Systematic Review. Dangour, A.D., S.K. Dodhia, A . Hayter, E. Allen, K. Lock , and R. Uauy. Am. J. Clin. Nutr.: 29 July 2009.
  DOI: 10.3945/ajcn.2009.28041. www.ajcn.org
• Priorities for Realizing the Potential to Increase Agricultural Productivity and Growth in Western and Central Africa. Nin-Pratt et al. IFPRI Discussion Paper 00876. 2009. www.ifpri.org

Potassium Dynamics in Root-Zone and Non Root-Zone in Yellow Cinnamon Soil with Paddy-Upland Rotation

Potassium dynamics in the root-zone and the non root-zone in yellow cinnamon soil with a rapeseed-rice rotation system was studied through a rhizobox device to provide evidence for research on soil K supplying mechanism and reasonable control of rhizosphere nutrition. The results show that soil water soluble K and exchangeable K in the root-zone are reduced at early stage of rapeseed growth under the rapeseed-rice rotation. Along with rapeseed growth and K uptake, soil non-exchangeable K in the root-zone are also decreased significantly. Soil water soluble K in the inner (0-20 mm), middle (20-40 mm) and outer (40-60 mm) parts of the non root-zone are moved forward to the root-zone. Soil exchangeable K and non-exchangeable K are transformed to water soluble K and decreased gradually. In the early stage of rice growth, water-log cultivating practice promotes the diffusion of soil water soluble K from the non root-zone to the root-zone and transition of exchangeable K to water soluble K. Along with the growth of rice and more K uptake, soil non-exchangeable K in each part is decreased significantly, while soil water soluble K and exchangeable K are not decreased. These results indicate that K uptake by crops is mainly contributed by the root-zone, and K in the non root-zone can be moved to the root zone gradually depending on the distance. Within the rotation system, soil non-exchangeable K is the main potassium source, followed by soil exchangeable K and water soluble K.

Correlation and Calibration of Soil Potassium Availability with Rice Yield and Nutritional Status

Soil testing is an important tool for estimating soil K availability and determining how much fertilizer must be applied to realize crop yield potential and minimize fertilizer costs. Our primary objectives were to correlate relative rice (Oryza sativa L.) yield with Mehlich-3 and 1 mol L^-1 HNO₃ extractable K, define sufficient whole-plant K concentrations at panicle differentiation (PD) and early heading (HDG), and calibrate K-fertilizer rates with Mehlich-3 soil K in the direct-seeded, delayed-flood rice production system. Potassium rate experiments were established at 32 site-years on silt loams in eastern Arkansas. Relationships between selected parameters were evaluated with linear, curvilinear, and linear-plateau models. The relationships between relative yield regressed against Mehlich-3 and HNO₃ extractable K were significant and curvilinear. The final curvilinear models for Mehlich-3 and HNO₃ K explained 63 and 43% of yield variability among site-years, with predicted critical soil concentrations to produce 95% relative yield of 99 and 390 mg K kg^-1, respectively. Linear-plateau models provided comparable critical soil K concentrations. Rice having whole-plant K concentrations of 23.1 g kg^-1 at PD and 13.0 g kg^-1 at HDG were predicted to produce 95% relative yield. The predicted K-fertilizer rates required to optimize rice grain yield depended on the model and ranged from 51 to 90, 41 to 70, 30 to 55, and 20 to 35 kg K ha^-1 for soil having Mehlich-3 soil K concentrations of 60, 70, 80, and 90 mg K kg^-1, respectively. The suggested Mehlich-3 soil and plant K critical concentrations should be appropriate for other U.S. mid-South rice-producing areas using similar cultural production practices.

Effects of Long-Term Potassium Application on Q/I Relationship of Potassium in Soil Under Wheat-Corn Cropping System

Quantity/intensity (Q/I) relationship of potassium (K) in soil was evaluated under a long-term K fertilization experiment. Soil samples collected from the NP and NPK treatments in the three soils (manural loess soil, fluvo-aquic soil and red soil) were analyzed for revealing the Q/I relationship of K, and the relationships between Q/I parameters and soil properties using Q/I approach under a 15 year wheat-corn cropping system. The values of K⁺ equilibrium activity ratio (AR₀), soil labile K (K_L), non-specific K (-ΔK₀), and specific K (K_X) in the NPK treatments are larger than those in the NP treatments. The AR₀ and -ΔK₀ values in the NPK treatments are 13.78 and 12.17 times larger than those in the NP treatments in red soil. The potential buffering capacity (PBC) is decreased (ranging from 17% to 20%) in the NPK treatments in manural loess soil and fluvo-aquic soil, and is not changed in red soil compared with those in the NP treatments. Free energies of K⁺ exchange for Ca²⁺ and Mg²⁺ (-ΔG) in the treatments with K fertilization are lower than those in the treatments without K application (12.15~12.81 vs 13.69~19.33 kJ/mol). There are significant correlations between the Q/I parameters and the 1 mol/L HNO₃ extractable K, K⁺ saturation and soil organic matter. The Q/I parameters provide useful information for understanding the soil K status. Soil K supplying power is increased due to the long-term K fertilization, while, continuous cropping without K inputs could cause the remarkable depletion of available K especially in the fluvo-aquic soil and red soil.

Productivity Enhancement of Jute through Balanced Application of N, P and K

The impact of balanced application of N, P and K on productivity of jute and jute based cropping systems had been evaluated. The contribution of fertiliser application to fibre yield of jute was found highest and was closely followed by weed management in farmer

Effects of Different Magnesium Nutrition on Root Growth and Physiological Characteristics of Rice

Magnesium (Mg) is one of the essential nutrients for higher plants. It plays an essential role in photosynthesis and many other metabolic processes. Rice (Oryza sativa L.) plants were grown in hydroponics culture at three Mg²⁺ levels under a greenhouse conditions to investigate the effects of different Mg concentrations on root growth, Mg uptake and some related physiological characteristics of rice. The results showed that root dry matter weight, root to shoot ratio, total root length, root activity, bleeding sap flow rate, the concentrations of total free amino acids and Mg in bleeding sap, Mg influx rate and Mg uptake rate of rice were significantly related to Mg supply levels. At low Mg²⁺ supply (0.05 mmol/L), rice plants partitioned larger proportion of dry matter to the roots causing to an increase of total root length and root to shoot dry weight ratio before Mg deficiency in rice leaves, which might be one of adaptive low-Mg-stress mechanisms of rice at early growth stage. Moderate Mg²⁺ supply (1.0 mmol/L) was able to promote plant growth and development, increase dry matter yield, and enhance root activity and bleeding sap rate as well as the total free amino acids contents. Root activity and amino-synthesized power might be restained to a certain extend by low or high levels of Mg²⁺ (5.0 mmol/L). The results also showed that Mg uptake, Mg concentrations in the bleeding saps, average Mg influx rate and the Mg uptake rate were significantly increased with an increase of Mg²⁺ concentrations in the nutrient solution.

Effects of Free Air Carbon-Dioxide Enrichment on Soil Available K in Rice-Wheat Rotation System

The effect of elevated athmospheric CO₂ on soil available K in paddy soil through FACE (Free air carbon dioxide enrichment) system was studied by comparing the contents of soil available K at different growth stages of the rice-wheat rotation system. The results show that compared to the ambient air treatment, K uptakes of the crops are increased by elevated CO₂ due to significant increase of their biomass, while the contents of soil available K of both upper soil layer (0-5 cm) and lower soil layer (5-15 cm) are not decreased. The increase magnitudes of soil available K due to elevated CO₂ are 6.3%-22.3% in root rhizosphere and 3.7%-11.2% between crops lines. The increment of soil available K around wheat roots is higher than that of rice. These results indicate that root increased by elevated CO₂ is beneficial to soil available K for crops, and K is not a limited factor for response of crops to elevated CO₂ in a short time. However, this phenomenon may have negative effects for soils with poor fertility.

Effect of Combined K and N Application on Yield, Qualities and K Absorption of Ginger

Field experiment was carried out to study the effect of combined potassium (K) and nitrogen (N) application on yield, qualities and K uptake in ginger (Zingiber officinale) rhizome. The results showed that there was an obvious response of ginger growth and qualities to the combined N and K application. A suitable rate and ratio of K and N combined application could obviously promote ginger growth, increase rhizome yield, improve nutrition qualities and enhance K recovery efficiency. The rhizomatous yield and its components increased with the increase of K application rates as it applied with less than K₂O 450 kg/ha. The largest values of plant height, branches number, stem diameter, dry weight of shoot and weight of single rhizome were found in K₄₅₀ (medium K application rate). The maximum rhizomatous yield was attained by the treatment N₄₅₀K₄₅₀. The results of quality analyses indicated that a suitable K and N application ratio could improve the nutrition qualities by increasing the content of vitamin C and sugar and dropping the concentration of nitrate in ginger rhizome. Combined application of N and K increased the content of vitamin C in rhizome compared single K application, and the highest content was obtained by the treatment of K₄₅₀. But there were no significant effects of raising N application rate to vitamin C. K application increased the concentration of soluble sugar and sucrose, but it differed with the combined N and K application rate. The concentration of nitrate increased significantly with the increase of N application rate at low K application, but it showed an opposite trend with high K application rate. The lowest content of nitrate was attained in N₃₇₅K₃₇₅ and N₄₅₀K₄₅₀. K application significantly improved the concentration of K in ginger shoot, rhizome and total plant, and enhanced K absorption compared to control. The concentration and uptake of K in ginger shoot, rhizome and total plant also increased obviously as increased N application rate at the same K application rate. The agricultural efficiency of K was highest in K₄₅₀ and it declined with the increase of K application rate at low rate of N application. The highest K recovery efficiency was obtained in K₄₅₀ with two N application rates.

Effects of N, P and K Application on Merchandise Properties and Yields of Welsh-Onion (Allium fistulosukm)

The effects of N, P and K application on stem length, stalk width, yield of welsh onion (Allium fistulosukm) and benefit of the fertilization were studied in the field by using the 311-A optimum regression design of supposed saturation. The results show that the optimum N, P and K application amounts for the maximum stem length of welsh-onion (92.88 cm) are N 371.30, P₂O₅ 157.50, and K₂O 309.58 kg/ha; the optimum application amounts for the maximum stalk width of the crop (1.769 cm) are N 350.63, P₂O₅ 157.50, and K₂O 225.00 kg/ha; and those for the maximum yield (55805.06 kg/ha) are N 394.08, P₂O₅ 193.62, and K₂O 225.00 kg/ha. The optimum N, P and K application amounts for the best fertilization benefit are N 391.35, P₂O₅ 192.97 and K₂O 225.00 kg/ha. The best fertilization benefit is about 136865.6 Yuan/ha with a yield of 55802.74 kg/ha.

Potassium Fertilisation Recommendations for Crops Need Rethinking

Potassium is an essential plant nutrient and adequate K fertilisation is must for successful crop production. Current recommendations for K fertilisation are based on exchangeable-K in surface 0-15 cm soil. However, available reports suggest that non-exchangeable-K and sub-soil K contributes significantly towards K uptake by crops. These factors therefore need to be taken into account along with exchangeable-K for making fertiliser recommendations for crops. Red and lateritic soils, which occur in east, northeast and southern India, are the poorest in K and need K fertilisation beyond the standard N:P:K ration 4:2:1. Black soils, which have a high exchangeable-K content are poor in non-exchangeable-K and total K and therefore need adequate K fertilisation to prevent K mining of soils.

Doses e Formas de Aplica

The main objective of this study was to evaluate the efficiency of potassium fertilizer application, as related to rate, placement (in-row, broadcast, and split topdress) and time (before sowing, at sowing, and topdressing), in a soybean, pearl millet, and cotton no-till rotation system, in a typic dystrophic Red Latosol (Hapludox), in Turvel