DETERMINING SOCIALLY OPTIMAL NITROGEN APPLICATION RATES USING A DELAYED RESPONSE MODEL: THE CASE OF IRRIGATED CORN IN WESTERN KANSAS

A delayed response model was used to examine the optimal nitrogen application for irrigated corn in western Kansas. Results show that taking into account the effect of leached nitrate on groundwater pollution reduces the profit-based nitrogen recommendation by 12.5% with a consequent reduction of the static profit of 6.7%.Crop Production/Industries,

DETERMINING SOCIALLY OPTIMAL NITROGEN APPLICATION RATES USING A DELAYED RESPONSE MODEL: THE CASE OF IRRIGATED CORN IN WESTERN KANSAS

Nitrate contamination of groundwater is an important problem. The transport of leached nitrate from the root zone to groundwater takes approximately 30 to 60 years. Many previous studies ignore this time lag by assuming instantaneous contamination. This analysis applies a delayed response model to account for the time lag between nitrogen fertilizer applications to the time the leached nitrate reaches groundwater. Results show that accounting for the leached nitrate externality reduces the nitrogen application rate by 13% and the returns above variable costs by 8% for farmers who apply both nitrogen and phosphorus. For farmers who do not use phosphorus, nitrogen use is reduced by 14% and the returns above variable costs by 22%. The application of phosphorous increased returns by more than 100% and significantly reduced leached nitrate.Crop Production/Industries,

Constraints to fertilizer use in Nigeria

Fertilizer consumption rates in Nigeria remains among the lowest in the world despite decades of aggressive subsidization. The extension service in Nigeria has a double-edged impact on fertilizer use in the country; not only can their activities increase farmers’ demand for fertilizer, but also the organizational framework of the service, Agricultural Development Programs, is the major source of fertilizer for farmers. To provide insights on the reasons for the low fertilizer use in Nigeria, this paper presents an analysis of the extension service as well as some perspectives of village extension agents. We find that the reach of the extension service is severely limited by low staff. The main technology transmitted is the use of improved seeds. Fertilizer technology is seldom transmitted and very rarely is irrigation taught. Furthermore, extension agents are found to have gaps in their knowledge of fertilizer technology. Extension agents routinely distribute agricultural inputs and many see their advisory role as secondary to this function. Extension agents identified the primary constraint to fertilizer use in Nigeria as the physical absence of the product at the time that it is needed, rather than lack of affordability or farmers’ lack of knowledge about the benefits or the use of fertilizer.Agricultural growth and technologies, Extension, Fertilizer, Subsidies,

Decentralization and rural service delivery in Uganda:

Decentralization, Development strategies, rural service delivery,

Heterogeneous treatment effects of integrated soil fertility management on crop productivity: Evidence from Nigeria

This study compares the impacts of integrated soil fertility management (ISFM) on crop production with use of either mineral fertilizer or organic manure alone. We also investigate the conditions under which .ISFM technology has greater beneficial effects on yields and the factors constraining its uptake. To answer these questions, the study uses a cross-sectional, plot-level data set collected in Nigeria by the International Food Policy Research Institute and the World Bank in 2009. Using both quasi experimental matching estimators and multivariate regression approaches, it finds that overall ISFM has robustly significant positive effects on crop production. The study also finds that ISFM positively affects crop production on plots with customary tenure, sandy soils, and clay soils—conditions that are normally perceived to be less favorable for crop production. The results also show ISFM to be more effective on plots with mild erosion or no erosion. On the constraints, we find that households with limited livestock, equipment, labor, and land are less likely to use ISFM technology, and the extension services currently do not seem to be disseminating ISFM. This evidence provides strong support for efforts to promote ISFM in Nigeria and in other regions with comparable conditions, but adequate attention must be paid to the biophysical conditions of the plots and the household's access to labor endowments, livestock, equipment, and tenure conditions if this technology is to be scaled up and more widely used in Sub-Saharan Africa.Crop production, Integrated soil fertility management, matching estimators,

The Influence of Asset and Access Poverty on Crop Production and Land Degradation in Uganda

This study investigated the linkages between poverty, agricultural productivity and land degradation in Uganda. Results show that farmers in the study region of Uganda deplete about 1.2% of the nutrient stock stored in the topsoil per year, leading to a predicted 0.2% annual reduction in crop productivity. Replacing the depleted nutrients using the cheapest inorganic fertilizers would cost about 20% of farm income on average. Land investments such as soil and water conservation structures and agroforestry trees were found to increase agricultural productivity and reduce land degradation. We observed an inverse farm size crop productivity relationship. Larger families are more productive but use more erosive practices in crop production. Participation in agricultural extension, especially the new National Agricultural Advisory Services program, and access to credit and markets are associated with increased productivity but have insignificant impacts on land degradation. Education is associated with greater productivity, but also with more soil nutrient depletion. Access to roads is associated with less soil nutrient depletion. We find no significant differences in crop productivity associated with differences in land tenure systems, though land degradation is greater on mailo than freehold land. Our results show that promotion of agricultural modernization through technical assistance and credit programs, investments in infrastructure and education can improve agricultural productivity. However, they also show that many of these investments do not necessarily reduce land degradation, and some may contribute to it. Thus, investing in agricultural modernization should be complemented by greater efforts to address land degradation.Crop Production/Industries, Land Economics/Use, Q24,

Understanding gender differences in agricultural productivity in Uganda and Nigeria

We investigate gender differences in agricultural productivity using data collected in 2005 from Nigeria and in 2003 from Uganda. Results indicate that lower productivity is persistent from female-owned plots and female-headed households, accounting for a range of socioeconomic variables, agricultural inputs, and crop choices using multivariate Tobit models. These results are robust to the inclusion of household-level unobservables. However, productivity differences depend on the type of gender indicator used, crop-specific samples, agroecological region, and inclusion of biophysical characteristics. More nuanced gender data collection and analysis in agricultural research spanning diverse regions are encouraged to identify interventions that will increase productivity and program effectiveness for male and female farmers.Agricultural productivity, Gender,

An econometric investigation of impacts of sustainable land management practices on soil carbon and yield risk: A potential for climate change mitigation

We investigate the impacts of sustainable land management practices on soil carbon stocks and also impacts of soil carbon on the mean and variance of crop production using econometric tools. Using a cross-sectional plot-level dataset collected from three agroecological zones of Uganda with soil carbon measured at a depth of 0 to 15 centimeters, our results have robustly shown that irrigation, fertilizers, improved fallow, crop residues, mulching, and trash lines are positively and significantly associated with higher soil carbon, corroborating results from agronomic experiments. However, we found crop rotation associated with lower soil carbon, which has also been observed in some agronomic experiments. Soil carbon has shown a significant nonlinear effect on crop production with the threshold occurring at 29.96 milligrams of carbon per hectare, above which farmers start to see significant positive effects on crop production. Furthermore, we found soil carbon to be associated with lower variance of crop production; hence, soil carbon is an indicator of crop yield loss risk (soil carbon has a risk-reducing effect). These empirical results have demonstrated strong evidence for developing countries of the potential of sustainable land management practices to enhance carbon sequestration and also the potential of soil carbon to reduce production risk. The results have implications for the role that soil carbon can play in adaptation to climate change and provision of ecosystem services.Land management, Climate change, soil carbon, Production risk, Carbon sequestration, Just and Pope stochastic production function,

DETERMINANTS OF SOIL NUTRIENT BALANCES AND IMPLICATIONS FOR ADDRESSING LAND DEGRADATION AND POVERTY IN UGANDA

A regression model was used to investigate the determinants of soil nutrient depletion in Uganda. The major determinants of soil nutrient balances are household endowments, access to markets, and extension services, non-farm activities and agricultural potential. The results suggest the need to address soil nutrient depletion using multi-sectoral approaches.Farm Management,

Linkages between poverty and land management in rural Uganda: evidence from the Uganda National Household Survey, 1999/00

"This study investigates the impacts of rural poverty on farmers' land management decisions, crop production and incomes, based upon analysis of data from the 1999/2000 Uganda National Household Survey. We find that the impacts of rural poverty on land management, crop production and income depend upon the type of poverty (i.e., what asset or access factor is constrained) and the type of land management considered...Our results suggest that improvement in smallholders' access to land, other assets, education, extension, market information, credit, roads, and off-farm opportunities can help to break the downward cycle of poverty and land degradation, and put farmers on a more sustainable development pathway. Access to land (area and quality), other assets, education and off-farm opportunities appear to be particularly important in addressing poverty directly, while other interventions are likely to have more indirect impacts, as they influence land management, crop choice, and other livelihood decisions. Given the importance of land as the major asset owned by poor rural households in Uganda, investing in land quality maintenance and improvement is a critical need. However, we found low marginal returns to investments in organic or inorganic fertilizer and other land management practices, suggesting that it will be difficult to get farmers to make such investments in the present environment. Improvements in the market environment as well as development of more profitable land management technologies appears essential to address this need." from Authors' Abstract