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Takeshima H.,International Food Policy Research Institute | Nagarajan L.,International Fertilizer Development Center
Environment and Development Economics | Year: 2012

Although farmer market participation raises income, it often also reduces on-farm varietal diversity. However, for under-utilized crops like minor millets, market participation may actually encourage growers to increase on-farm diversity through better access to new varieties exchanged at local markets and higher returns from varieties already grown. We test this hypothesis in two different agro-ecological niches, the Plains and the Hills in southern India. Empirical results based on propensity score matching indicate that, in the less fertile dryland plains, market participation improved on-farm varietal diversity of minor millets and increased net revenues - albeit with insignificant welfare effects on farm households. On the other hand, in the fertile hill ecosystems, market development had no effect on varietal diversity. Insights from such a comparison could help design suitable policy interventions for on-farm conservation of under-utilized crops in their own agro-ecosystems through active stakeholder participation. © Copyright 2012 Cambridge University Press. Source

Chien S.H.,International Fertilizer Development Center | Sikora F.J.,University of Kentucky | Gilkes R.J.,University of Western Australia | McLaughlin M.J.,CSIRO
Nutrient Cycling in Agroecosystems | Year: 2012

This article presents a critical discussion comparing the traditional method and a newly proposed balance method to calculate percent recovery of fertilizer P applied to soils. The traditional difference method is defined as P uptake from the soil treated with fertilizer P minus P uptake from a control with no P added divided by the amount of fertilizer P applied. The balance method simply considers the ratio of P uptake from the P fertilized soil to the amount of fertilizer P applied and does not use a control to discount P taken up from soil without fertilizer application. The percentage recovery of fertilizer P calculated by the difference method normally ranges from 10 to 25% for a given crop in a given season and is always lower than that by the balance method which ranges from 50 to 90% and is sometimes over 100%. The balance method is inappropriate to calculate percentage recovery of current fertilizer P applied due to its overestimation and the invalidity of the mathematical equation used. The difference method is superior to the balance method to estimate percentage recovery of fertilizer P applied. The balance method is suitable for determining a percent soil P balance to evaluate if fertilizer P applications are building up, depleting, or maintaining soil P reserves. © 2011 Springer Science+Business Media B.V. Source

Agyin-Birikoran S.,International Fertilizer Development Center | Newman Y.C.,University of Florida | Kasozi G.N.,University of Florida
Crop Science | Year: 2012

Nitrogen is a critical element for sustainable for age production but N surpluses in sandy soils could result in nitrate leaching and water contamination. Our objective was to identify a N application rate that optimizes yield and quality of 'Tifton 85' bermudagrass (Cynodon Rich. spp.) with minimal N leaching losses in a typical Florida sandy soil. Four N application rates (30, 50, 70, and 90 kg N ha-1 per harvest) and an unfertilized (0 N) control in a Tifton 85 bermudagrass hay field were evaluated. Suction lysimeters were installed in each plot at 30 and 100 cm below the soil surface to measure soil water nitrate concentration. Nitrogen application at the recommended rate of 90 kg N ha-1 per harvest produced the greatest total dry matter yield (DMY) (~22 Mg ha-1 yr-1), but a modeled optimum DMY of ~18 Mg ha-1 yr-1 occurred at 57 kg N ha-1 per harvest. Nitrogen application increased herbage nutritive value, but the difference was not significant above 30 kg N ha-1 per harvest. Treatments with N rates ≤ 50 kg N ha-1 per harvest had leachate nitrate concentration below the maximum contaminant limit (MCL) of 10 mg L-1. However, N rates ≥ 70 kg N ha-1 per harvest had leachate nitrate concentration that exceeded the MCL, suggesting a risk of impacting groundwater quality. The results demonstrate that although Tifton 85 bermudagrass is an efficient N remover, there is potential for N leaching in sandy soils. Therefore, site-specific evaluation of appropriate N management is critical. © Crop Science Society of America. Source

Chien S.H.,International Fertilizer Development Center | Gearhart M.M.,Honeywell | Villagarcia S.,Agrarian National University
Soil Science | Year: 2011

Ammonium sulfate (AS) provides critical plant nitrogen (N) and sulfur (S) nutrients. Compared with other N fertilizers, such as urea and ammonium nitrate (AN), AS may have some potential agronomic and environmental benefits. These are (i) no potential toxicity of aqueous NH3 and nitrite to plants in alkaline soils; (ii) no N loss via NH 3 volatilization when surface applied to acid or neutral soils; (iii) a better N source for saline soils by decreasing the negative specific effects of NaCl on plant growth and for saline sodic calcareous soils by improving soil structure; (iv) positive effects of soil acidification on increasing availability of soil phosphorus (P) and applied phosphate rock and soil and applied micronutrients; (v) no contribution of CO 2 emission to greenhouse gases; (vi) a potential to use AS to reduce NH 3 volatilization from urea and enhance N efficiency of urea; (vii) more acidic root rhizosphere via preference absorption of NH 4-N of AS to NO 3-N of AN that may increase availability of soil P, applied phosphate rock, and micronutrients; (viii) less NO 3-N leaching from AS than AN can increase N efficiency and reduce NO 3-N pollution in groundwater and eventually drinking water; and (ix) less denitrification with AS than AN that may increase N efficiency and minimize greenhouse gases (NO and N 2O). Ammonium sulfate is more effective than granulated elemental S (ES) or ES-enriched NP fertilizers to provide S nutrient because AS is water soluble, whereas ES requires S oxidation to SO 4-S. The possible negative effects of AS compared with other N and S fertilizers are high soil acidification may require more liming and a higher cost per unit of N applied. However, the N cost of AS includes free S nutrient. Copyright © 2011 by Lippincott Williams & Wilkins. Source

Chien S.H.,International Fertilizer Development Center | Rehm G.W.,University of Minnesota
Soil Research | Year: 2016

Efficiency of use of various phosphate fertilisers is affected by water-insoluble reaction products such as Fe-P, Al-P, and Ca-P in either discrete precipitates or surface-adsorbed forms. A product, maleic-itaconic acid copolymer, has been marketed for increasing efficiency of use of phosphate fertilisers. Field trials have been conducted to evaluate the agronomic effectiveness of this product with no measured positive effects. This absence of positive effects can be explained if fundamental principles of chemistry are considered. The negative logarithm of the equilibrium constant (pK) of CaHPO4.2H2O (DCPD) is higher than that of Ca-maleic acid and Ca-itaconic acid complexes. Therefore, the copolymers cannot prevent DCPD formation in calcareous soils. Likewise, because of the pK values of Fe-maleic, Fe-iticonic acid, Al-maleic acid, and Al-itaconic acid are lower than those values for AlPO4.2H2O, and FePO4.2H2O, the copolymer cannot block or prevent formation of AlPO4.2H2O and FePO4.2H2O in acid soils. The results of agronomic greenhouse and field trials can be explained by the considerations of the solubility-product constant or the dissociation constant of cation-chelate for various reactions. Therefore, the copolymer marketed has little value for increasing P efficiency from phosphate fertilisers as claimed by the manufacturer. Journal compilation. © CSIRO 2016. Source

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