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Waswa B.S.,University of Bonn | Vlek P.L.G.,University of Bonn | Tamene L.D.,International Center for Tropical Agriculture | Okoth P.,International Center for Tropical Agriculture | And 2 more authors.
Geoderma | Year: 2013

Understanding the patterns of land degradation indicators can help to identify areas under threat as basis for designing and implementing site-specific management options. This study sort to identify and assess the patterns of land degradation indicators in selected districts of western Kenya. The study employed the use of Land Degradation Sampling Framework (LDSF) to characterize the sites. LDSF a spatially stratified, random sampling design framework consisting of 10. km × 10. km blocks and clusters of plots. The study broadly identified and classified the indicators and attributes of land degradation into soil and site stability, hydrologic function and biotic integrity. Assessment of general vegetation structure showed that over 70% of the land was under cropland with forests accounting for 8% of the area. Sheet erosion was the major form of soil loss. High variability was observed for the soil properties and this can be due to both inherent soil characteristics as well as land management practices. There was distinct variation in the soil properties between the topsoil (0-20. cm) and the subsoil (20-30. cm) with the topsoil having higher values for most of the parameters compared to the subsoil. Using coefficient of variation (CV) as criteria for expressing variability, Ca, TON, Mg, SOC and silt were most variable soil properties for the 0-20. cm depth. Moderate variability (CV 0.15-0.35) was observed for CEC, P, K and clay while Na, Sand and pH had the least variability (CV < 0.15). For the subsoil (20-30. cm), Ca, Mg and silt were the most variable. About 94% of the farms sampled were recorded to have very strongly acidic soil levels (pH. 4.5-5.5) while 6% of the farms had moderately acidic soil levels (pH. 5.6-6.0). Over 55% of the farms had low (< 2%) total organic carbon levels and this varied with land use. Soils with SOM below this 'critical level' are at a threat of degradation if not well managed. The principal component analysis (PCA) identified three main explanatory factors for soil variability: 'soil fertility potential', 'soil physical properties' and 'available P'. Improving productivity of land therefore calls for the adoption of integrated soil fertility management (ISFM) options as a strategy to ensuring nutrient availability while at the same time building the natural nutrient reserve through soil organic matter build up. © 2012 Elsevier B.V.

Pasuquin J.M.,International Plant Nutrition Institute IPNI | Pasuquin J.M.,International Rice Research Institute | Pampolino M.F.,International Plant Nutrition Institute IPNI | Witt C.,International Plant Nutrition Institute IPNI | And 5 more authors.
Field Crops Research | Year: 2014

Rising incomes and changing dietary requirements are swiftly transforming maize (Zea mays L) in Southeast Asia from a food staple into an important industrial commodity. Increased maize production is required to meet rising demands, but additional production should come from the sustainable intensification of existing farmlands to minimize the undesirable effects of agriculture on the environment. We hypothesize that maize yields, profit, and N use efficiencies can be significantly increased through site-specific nutrient management (SSNM), thereby reducing yield gaps in the region. Through a combined approach of simulation modeling and on-farm research in at least 65 sites in 13 major maize-producing domains across Indonesia, Vietnam and the Philippines from 2004 to 2008, we were able to (a) quantify maize yield gaps and yield responses to fertilizer application, (b) evaluate the agronomic and economic performance of SSNM, and (c) evaluate the incremental profitability of SSNM in various production and grain and fertilizer price scenarios. The average exploitable yield gap between the attainable yield and current farmers' yield in Southeast Asia was about 0.9tha-1. Yield responses to fertilizer application across the region followed the order N>>P>K. Yield response to N was higher in irrigated sites than in rainfed sites (6tha-1 versus 2tha-1), while P and K fertilizer responses were similar across production systems (<2tha-1). Yield with SSNM was 1.0tha-1 (+13%) higher than the current farmers' fertilizer practice (FFP) measured in the same cropping seasons. Yield increases were associated with a 10% decrease in the average N rate, but with increased application of K at sites where the previous K rates were low. Average N use efficiency increased by 42%, mainly by adjusting the rates and timing of N application to the stages of crop development. Across all sites and seasons, profitability increased by US$167ha-1 per crop, which was equivalent to15% of the total average net return. Opportunities for achieving higher income over the FFP (≥US$100ha-1 season) were greatest in highly favorable rainfed environments; less favorable rainfed areas were vulnerable to unfavorable market prices. We conclude that SSNM has the potential to close existing yield gaps in the maize production systems of Southeast Asia by improving yield, nutrient use efficiency, and profitability. © 2013 .

Pampolino M.F.,International Plant Nutrition Institute IPNI | Witt C.,International Plant Nutrition Institute IPNI | Witt C.,Bill and Melinda Gates Foundation | Pasuquin J.M.,International Plant Nutrition Institute IPNI | And 2 more authors.
Computers and Electronics in Agriculture | Year: 2012

Meeting the demand for more food in the next 20-30years requires intensifying cereal cropping systems and increasing current yields to about 70-80% of the genetic yield potential. A dynamic and robust nutrient management approach such as site-specific nutrient management (SSNM) will be essential to increase yields and optimize profits while maintaining the productivity of these intensive cropping systems. SSNM has increased yield and profit in rice, maize, and wheat in major cropping systems in Asia; but, crop advisors have found it complex and difficult to implement in the field. Nutrient Expert (NE) was developed to provide crop advisors with a simpler and faster way to use SSNM. NE enables crop advisors to develop SSNM recommendations using existing site information. Nutrient Expert for Hybrid Maize (NEHM) increased yield and profit of farmers in Indonesia and the Philippines. In Indonesia, NEHM increased yield by 0.9tha -1, which increased profit by US$ 270ha -1 over farmer's fertilizer practice (FFP). Compared with FFP, NEHM recommendations reduced fertilizer P (-4kgha -1), increased fertilizer K (+11kgha -1), and did not significantly change fertilizer N. In the Philippines, NEHM increased yield by 1.6tha -1 and profit by US$ 379ha -1 compared with FFP. Compared with FFP, NEHM gave higher rates of all three nutrients (+25kgNha -1, +4kgPha -1, and +11kgKha -1), which substantially increased fertilizer costs (US$ 64ha -1) but still increased profit by about six times the additional investment in fertilizer. NE accounts for the important factors affecting site-specific recommendations, which makes it a suitable starting point for developing nutrient management tools to reach more users. © 2012 Elsevier B.V.

de Oliveira Jr. A.,Embrapa Soja | Prochnow L.I.,International Plant Nutrition Institute IPNI | Klepker D.,Embrapa Soja Setor Experimental de Balsas
Scientia Agricola | Year: 2011

Soybean (Glycine max L. Merrill) crop started to be planted in the Brazilian Cerrado in the 1970's, and this region currently contributes with 57% of total soybean production in Brazil. Under natural conditions in this region, the soils present chemical limitations such as low pH, low Cation Exchange Capacity, low nutrient availability, and moreover, clayey soils have a high P fixation capacity mainly due to high contents of Fe/Al oxides. Since P is the most limiting nutrient is this region, a study was performed in the state of Maranhão, Brazil, in a Typic Hapludox, with clayey texture and low available P (extracted by resin). Treatments were defined to evaluate soybean response to broadcast Arad phosphate rock (PR) plus banded triple superphosphate (TSP) and to evaluate the soybean response to three proportions of PR and TSP. The experiment was established in October 2004 and was carried out for three consecutive crop years (2004/05 to 2006/07). The associated use of PR and TSP, in several situations, resulted in yields at least similar to that obtained with the use of the water soluble P source and, in some cases, even using lower P rates. Regarding the "mixtures", a linear response was observed when they were banded; however, when they were broadcasted, no increase in yield was observed above 50% of relative solubility. In conclusion, the association of sources differing in solubility may be a feasible agronomic option for P fertilizer management of soybeans.

Buresh R.J.,International Rice Research Institute | Pampolino M.F.,International Plant Nutrition Institute IPNI | Witt C.,International Plant Nutrition Institute IPNI
Plant and Soil | Year: 2010

Fertilizer K and P requirements for rice (Oryza sativa L.) can be determined with site-specific nutrient management (SSNM) using estimated target yield, nutrient balances, and yield gains from added nutrient. We used the QUEFTS (QUantitative Evaluation of the Fertility of Tropical Soils) model with >8000 plot-level observations to estimate the relationship between grain yield and nutrient accumulation in above-ground dry matter of irrigated rice with harvest index≥0.4. Predicted reciprocal internal efficiencies (RIEs) at 60-70% of yield potential corresponded to plant accumulation of 14.6 kg N, 2.7 kg P, and 15.9 kg K per tonne of grain yield. These RIEs enable determination of plant requirements for K and P and net output of K and P in harvested grain and removed crop residues at a target yield. Yield gains for nutrient applied to irrigated rice averaged 12% for K and 9% for P for 525 to 531 observations. For fields without certain yield gain, fertilizer K and P requirements can be determined by a partial maintenance approach (i.e., fertilizer input

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