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Abstract:
To meet economic and environmental demands for about 10 billion people by the mid-21st century, humanity will be challenged to double food production from the Earth's soil and diminish adverse effects of soil management on the wider environment. To meet these challenges, an array of scientific approaches is being used to increase understanding of long-term soil trends and soil-environment interactions. One of these approaches, that of long-term soil experiments (LTSEs), provides direct observations of soil change and functioning across time-scales of decades, data critical for biological, biogeochemical, and environmental assessments of sustainability; for predictions of soil productivity and soil environment interactions; and for developing models at a wide range of scales. Although LTSEs take years to mature, are vulnerable to loss, and have yet to be comprehensively inventoried or networked, LTSEs address a number of contemporary issues and yield data of special significance to soil management. The objective of this study was to evaluate how LTSEs address three questions that fundamentally challenge modern society: how soils can sustain a doubling of food production in the coming decades, how soils interact with the global C cycle, and how soil management can establish greater control over nutrient cycling. Results demonstrate how LTSEs produce significant data and perspectives for all three questions. Results also suggest the need for a review of the state of our long-term soil-research base and the establishment of an efficiently run network of LTSEs aimed at soilmanagement sustainability and improving management control over C and nutrient cycling.

Comparison of Seven Kinetic Equations for K Release and Application of Kinetic Parameters. LU Xiao-Nan, XU Jian-Ming, MA Wan-Zhu and LU Yun-Ful. 2007. Pedosphere 17(1): 124-129.

Abstract:
Corn field experiments with two treatments, NP and NPK, where N in the form of urea, P in the form of calcium phosphate, and K in the form of KCl were applied at rates of 187.5, 33.3, and 125 kg/ha, respectively, on soils derived from Quaternary red clay were conducted in the hilly red soil region of Zhejiang Province, China. Plant grains and stalks were collected for determination of K content. Seven equations were used to describe the kinetics of K release from surface soil samples taken before the corn experiments under electric field strengths of 44.4 and 88.8 V/cm by means of electro-ultrafiltration (EUF) and to determine if their parameters had a practical application. The second order and Elovich equations excellently described K release; the first-order, power function, and parabolic diffusion equations also described K release well; but the zero-order and exponential equations were not so good at reflecting K release. Five reference standards from the field experiments, including relative grain yield (yield of the NP treatment/yield of the NPK treatment), relative dry matter yield (dry matter of the NP treatment/dry matter of the NPK treatment), quantity of K uptake in the NP treatment (no K application), soil exchangeable K, and soil HNO3 soluble K, were used to test the effectiveness of equation parameters obtained from the slope or intercept of these equations. Correlations of the Ymax (the maximum desorbable quantity of K) in the second-order equation and the constant b in the first-order and Elovich equations to all five reference standards were highly significant (P <0.01). The constant a in the power function equation was highly significant (P <0.01) for four of the five reference standards with the fifth being significant (P <0.05). The constant b in the parabolic equat i on was also significantly correlated (P <0.05) to the relative grain yield and soil HNO3-soluble K. These suggested that all of these parameters could be used to estimate the soil K supplying capacity and the crop response to K fertilizer.

Foliar K applications safe with glyphosate. Nelson, K., Motavalli, P., Stevens, G., Kendig, A., Nathan, M. and D. Dunn. 2007. Fluid Journal, Issue 56, Vol. 15, No. 2 - Spring 2007, pp 14-16.

Abstract:
Soybean injury resulting from foliar applications of up to 19.2 lbs/A of K2O from several potassium (K) fertilizer sources (i.e., potassium chloride, potassium thiosulfate, and 3-18-18) was generally less than 10 per cent. K fertilizer sources tank-mixed with glyphosate, such as 3-18-18 at 2.4 and 9.6 lbs K2O/A, 5-0-20-13 (KTS + urea-triazone) at 2.4 lbs K2O/A, and 0-0-62 at 9.6 and 19.2 lbs K2O/A, controlled more than 90 per cent of weeds and produced grain yields similar to herbicide applications with diammonium sulfate (DAS), while providing additional K fertilizer to the soybean plant in a single-pass weed management system in northern Missouri. However, two-pass weed management in southern Missouri provided excellent weed control for all additives, and grain yields were greater than or similar to glyphosate plus DAS. The results of the s tudy indicate that foliar K applications can be mixed with glyphosate with minimal crop injury and reduction in weed control, depending on product selection and application rate.
Link: http://www.fluidfertilizer.com/pastart/potassiu.htm.

Abstract:
Field experiments were conducted in 2003, 2004, and 2005 on a S-deficient Gray Luvisol (Boralf) soil near Star City, in northeastern Saskatchewan, to determine yield, seed quality and S uptake response of different Brassica (B.) oilseed species/cultivars to S deficiency and S fertilization. A total of 20 treatments were tested in a factorial combination of four oilseed crops (B. juncea canola cv. Arid, B. juncea canola cv. Amulet, B. juncea mustard cv. Cutlass, and B. napus cv. InVigor 2663 hybrid canola) and five rates of potassium sulfate fertilizer (0, 10, 20, 30, and 40 kg S/ha). All B. species/cultivars responded positively for seed yield and most other parameters to S fertilizer in all 3 yr, but the magnitude of response varied with species/cultivar and year. Seed yield was highest with Cutlass juncea mustard in a dry year (2003), but was highest with InVigor 2663 hybrid canola in years with above-average precipitation (2004 and 2005). Seed yield was usually maximized at the rate of 30 kg S/ha for all B. species/cultivars. Oil concentration in seed increased with S fertilization for all B. species/cultivars. There was a significant (albeit small) increase of protein concentration in seed due to S fertilization. Cutlass juncea mustard accumulated considerably high concentrations of glucosinolates in seed, but glucosinolate concentrations were low in other B. species/cultivars. Sulfur uptake in seed was highest with Cutlass juncea mustard in all years. The effects of S deficiency and applied S were more pronounced on seed than straw. In conclusion, S fertilizer requirements for optimum seed yield were similar for all the B. species/cultivars used in this study on S-deficient soil, but higher yielding types of B. would produce greater seed yield by using S more efficiently.

Abstract:
Grain sorghum [Sorghum bicolor (L.) Moench] is an important food crop of semi-arid sub-Saharan Africa. Crop yields are generally low, partly due to low soil fertility. Research was conducted with farmers to evaluate soil fertility management practices in sorghum-based cropping systems including: mucuna [Mucuna pruriens (L.) DC.] fallow; cowpea [Vigna unguiculata (L.) Walp.] rotation with sorghum; animal manure application; N and P fertilizer application; and reduced tillage. Four studies, comprised of 142 on-farm trials, were conducted at three locations over three years in drought-prone parts of eastern Uganda. Mucuna on average produced 7 Mg/ha of aboveground dry matter containing 160 kg N/ha across the three locations. Application of 2.5 Mg/ha of manure and of 30 kg N plus 10 kg P/ha increased grain yield by 1.05 and 1.30 Mg/ha, respectively. A combination of 2.5 Mg/ha manure with 30 kg N/ha increased grain yield by 1.50 Mg/ha above the control (1.1 Mg/ha). The increase in sorghum grain yield in response to 30 kg N/ha alone, to a mucuna fallow, and to a rotation with cowpea was 1.15, 1.55, and 0.82 Mg/ha, respectively. These soil fertility management practices, as well as reduced tillage, were found to be cost effective in increasing sorghum yield in the predominantly smallholder agriculture where inorganic fertilizer was not used much. On-farm profitability and food security for sorghum production systems can be improved by use of inorganic fertilizers, manure, mucuna fallow, sorghum-cowpea rotation, and reduced tillage.

Abstract:
A long-term fertilization experiment with monoculture corn (Zea mays L.) was established in 1980 on a clay-loam soil (Black Soil in Chinese Soil Classification and Typic Halpudoll in USDA Soil Taxonomy) at Gongzhuling, Jilin Province, China. The experiment aimed to study the sustainability of grain-corn production on this soil type with eight different nitrogen (N)-, phosphorus (P)-, and potassium (K)-mineral fertilizer combinations and three levels (0, 30, and 60 Mg ha/y) of farmyard manure (FYM). On average, FYM additions produced higher grain yields (7.78 and 8.03 Mg/ha) compared to the FYM0 (no farmyard application) treatments (5.67 Mg/ha). The application of N fertilizer (solely or in various combinations with P and K) in the FYM0 treatment resulted in substantial grain-yield increases compared to the FYM0 control treatment (3.56 Mg/ha). However, the use of NP or NK did not yield in any significant additional effect on the corn yield compared to the use of N alone. The treatments involving P, K, and PK fertilizers resulted in an average 24 per cent increase in yield over the FYM0 control. Over all FYM treatments, the effect of fertilization on corn yield was NPK > NP = NK = N > PK = P > K = control. Farmyard-manure additions for 25 y increased soil organicmatter (SOM) content by 3.8 g/kg (13.6%) in the FYM1 treatments and by 7.8 g/kg (27.8%) in the FYM2 treatments, compared to a 3.2 g/kg decrease (11.4%) in the FYM0 treatments. Overall, the results suggest that mineral fertilizers can maintain high yields, but a combination of mineral fertilizers plus farmyard manure are needed to enhance soil organic matter levels in this soil type.

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June 2007

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