Managing phosphorous soil dynamics over space and time

Understanding the relationship between soil fertility dynamics and crop response is conceptually appealing. Even more appealing is comprehension of the spatial and temporal heterogeneity of these connections over a production surface and across seasons. But gaining knowledge about these interactions is difficult because nutrient carryover dynamics and crop response to inputs are determined simultaneously on the one hand, and sequentially on the other. A second problem enters when crops are rotated, for example, the corn [Zea mays (L.) Merr.]–soybean [Glycine max (L.) Merr.] system commonly practiced in the U.S. Corn Belt. This article examines nutrient carryover–crop response dynamics using data from a corn‐soybean, variable rate nitrogen (N), and phosphorous (P) experiment conducted over five years in Minnesota, USA. Site‐specific corn response to N and P and soybean response to P is estimated with a P carryover equation. Estimates are used in a dynamic programming model to determine site‐specific optimal N and P fertilizer policies, soil P evolution, and profitability. The net present value of managing N and P site‐specifically is compared to a strategy in which these inputs are managed uniformly following Extension guidelines. The results suggest that when P carryover is accounted for in determining optimal P fertilizer rates, returns to the variable rate strategies are higher than returns to a uniform or whole‐field management strategy.     

The impact of marketing systems on soil sustainability of agriculture in developing countries: a method and an application

This article is concerned with soil‐sustainability problems of agriculture in developing countries, in particular with soil erosion. The aim of our study is to develop a comprehensive model that explains the adoption of sustainable agricultural practices with respect to soil conservation. Our approach includes the following special features: (a) the model is comprehensive in that it includes a large number of institutional, personal–social, economic, and physical explanatory variables; (b) particular attention is paid to the influence of marketing systems on the adoption of sustainable agricultural practices, which to our knowledge has been neglected in past research; (c) the concept of adopting sustainable agricultural practices (ASAP) is differentiated into a limited number of basic components of soil conservation; and (d) the model is estimated by Principal Component Regression, which enhances efficient estimation of the impact of many explanatory variables on ASAP. Our model is applied to Cabuyal hillside farming in Colombia. The application demonstrates the usefulness of the proposed model. ASAP is differentiated into three basic components: soil‐disturbance control, soil‐protection practices, and run‐off control. It appears that soil‐disturbance control is particularly influenced by farmers' characteristics, such as education and managerial variables. The second component, soil‐protection practices, appears to be strongly influenced not only by farmers' managerial variables but also by their relationship with their environment, in particular marketing institutions. The third soil‐conservation component, run‐off control, is influenced by the physical characteristics of the plot and by the available farm labor. Our empirical results demonstrate the usefulness of the proposed model in designing agricultural policies, because it can determine which variables are more likely to influence the adoption of a specific type of soil conservation.     

The impacts of biofuels targets on land‐use change and food supply: A global CGE assessment

We analyze the long‐term impacts of large‐scale expansion of biofuels on land‐use change, food supply and prices, and the overall economy in various countries or regions using a multi‐country, multi‐sector global computable general equilibrium model augmented with an explicit land‐use module and detailed biofuel sectors. We find that an expansion of biofuel production to meet the existing or even higher targets in various countries would slightly reduce GDP at the global level but with mixed effects across countries or regions. Significant land re‐allocation would take place with notable decreases in forest and pasture lands in a few countries. The expansion of biofuels would cause a moderate decrease in world food supply and more significant decreases in developing countries like India and Sub‐Saharan Africa. Feedstock commodities (sugar, corn and oil seeds) would experience significant increases in their prices in 2020, but other price changes are small.     

The economic impacts of technology and climate change: New evidence from U.S. corn yields

Over the past century, U.S. farmers have been offered a steady stream of new agricultural technologies, and more recently, experienced climate change. Because these two events have been occurring simultaneously, identifying their separate effects is difficult, and misimputation is easy. This article explicitly examines the economics of technical change and the interaction between weather and technology as revealed in a half century of panel data on U.S. Midwest rainfed state‐average corn yields. Observed yields reflect two components: yield potential and damage to the potential caused by weather and pests. Yield potential is modeled as a stochastic production frontier where nitrogen fertilization, public corn research, and introduction and adoption of biotech corn seeds impact yield potential and excess heat impacts nitrogen productivity. The yield‐damage/damage‐control function permits biotech corn plants to abate adverse effects of weather and pest events. Results include the following: nitrogen use, public corn research, and biotech seed‐corn adoption increase yield potential; soil moisture stress reduces yield potential, and excess heat severely reduces nitrogen productivity. Biotech corn plants abate yield damage caused by soil moisture stress but not excess heat.     

Impacts of tenancy arrangements on investment and efficiency: evidence from Pakistan

In this article, we use farm‐level data from the Punjab Province in Pakistan to analyze the impact of three tenancy contracts on investment in soil‐improving and productivity‐enhancing measures and farm productivity. A multivariate tobit model that accounts for potential substitutability and complementarity of investment options, as well as endogeneity of tenure arrangements was employed in the empirical analysis. Our empirical results indicate that land tenure arrangements influence farmers’ decisions to invest in soil‐improving and productivity‐enhancing measures. In particular, owner‐cultivators with secured tenancy arrangements were found to be more likely to invest in soil‐improving and productivity‐enhancing measures, compared to those on leased contracts. We also find that output per hectare was highest on land cultivated by owners and lowest on land under sharecropping tenancy, lending support to the Marshallian inefficiency hypothesis.     

An economic approach to soil fertility management for wheat production in north-eastern Australia

Soil fertility decline and soil management for crop production are important economic issues for grain growers in north-eastern Australia. In that region, there is evidence of soil fertility decline which is attributed to past crop management practices. The questions addressed in this article are first, whether components of soil fertility can be improved by better management and second, by how much soil fertility would change. Soil fertility for crop production is considered in terms of soil organic carbon and nitrogen. A stochastic dynamic economic analysis of soil fertility management for wheat production is presented. A sequential analysis of first deriving the optimal nitrogen stock and application rates is followed by an assessment of tillage, stubble, and fertilizer strategies to obtain an optimal level of soil organic carbon. The recommended management practices are consistent with emerging management trends in the region. The derivation of optimal levels of soil fertility for agricultural purposes has other policy implications, which we discuss.     

The productivity of agricultural credit in India

This study examines the nature of the relationship between formal agricultural credit and agricultural Gross Domestic Product (GDP) in India, specifically the role of the former in supporting agricultural growth, using state level panel data covering the period 1995–1996 to 2011–2012. The study uses a mediation analysis framework to map the pathways through which institutional credit relates to agricultural GDP relying on a control function approach to tackle the problem of endogeneity. The findings from the analysis suggest that over this period, all the inputs are highly responsive to an increase in institutional credit to agriculture. A 10% increase in credit flow in nominal terms leads to an increase by 1.7% in fertilizers (N, P, K) consumption in physical quantities, 5.1% increase in the tonnes of pesticides, 10.8% increase in tractor purchases. Overall, it seems quite clear that input use is sensitive to credit flow, whereas GDP of agriculture is not. Credit seems therefore to be an enabling input, but one whose effectiveness is undermined by low technical efficiency and productivity.     

Potential and limitation of an organic fertilizer‐based development strategy: evidence from Tamil Nadu,India, from 1993 to 2003

This article explores the potential and limitations for using farmyard manure (FYM) to improve paddy and upland cereals productivity under various soil conditions in Tamil Nadu, India. Using household‐level fixed effects, estimated yield functions from 1993 to 2003 confirm that FYM application directly increases crop productivity in upland cereals, but not in paddy rice. Complementary effects through an increase in the marginal product of inorganic fertilizer is observed for both paddy and upland cereals, especially where inherent soil fertility is low. Farmers’ FYM use is responsive to changes in the price of FYM, but transport costs limit price transmission across space. Dairy sector development thus improves crop productivity, but only in the small area around the animals which limits the spread of FYM‐based development strategy.     

Trade policy, biotechnology and grain self-sufficiency in China

Over the past 20 years the growth of China's agricultural economy has been extraordinary. However, it seems unlikely that China will maintain self‐sufficiency in grains by 2005 without substantial intervention. We develop a CGE model to assess the options available to Chinese policy makers. We compare the welfare effects of import tariffs and domestic support, and explore the potential of biotechnology as a means to achieve self‐sufficiency through improvements in agricultural productivity. Our results indicate that the price interventions that would be required to maintain China's desired self‐sufficiency ratios are considerable, and are unlikely to be compatible with WTO accession. The productivity improvements required are also significant, and likely beyond the current potential of biotechnology.     

Resource saving and productivity enhancing impacts of crop management innovation packages in Ethiopia

Crop management innovations are often not discrete fixed stand‐alone options—and their adoption may imply various combinations and adaptations. This potentially confounds their impact assessment. This article assesses the resource saving and productivity enhancing impacts of a crop management package revolving around minimum tillage in maize‐based farming systems in northwest Ethiopia. An endogenous switching regression model was applied to plot‐ and household‐level survey data collected from 290 rural households operating 590 maize plots during the 2012 production year. Controlling for variations in plot and household characteristics, the average effect of minimum tillage package (minimum tillage package) on maize productivity is 0.44 t/ha. Compared to conventional practice (CP), adoption of the MTP decreased the average male and female labor use in maize production by 14.4 and 8.2 person‐days per ha, respectively. Similarly, MTP adoption decreased draft power use for land preparation by 13.2 pair of oxen‐days per ha. Compared to CP, in general, there is a considerable short‐run maize productivity gain and reduction in labor and draft power use under MTP.     

Cost-effective nitrogen leaching reduction as influenced by linkages between farm-level decisions

This article focuses on how the linkages between various farm‐level decisions affect the choice of measures to reduce nitrogen leaching from crop production. A mathematical programming model is developed. The model considers not only management decisions that affect nitrogen leaching directly, but also other decision variables such as scheduling of field operations and machinery investments. A simplified analysis that ignores the latter management decisions, and the linkages between the various decisions, may result in abatement policies that are not cost‐effective because the policies will have other effects than expected. As an example, the empirical results show that subsidies to catch crops and spring ploughing may contribute to increased nitrogen load, quite contrary to the purpose of these subsidies. Further, it is noted that the characteristics of the production system make it costly to change land use, tillage practices, or fertilizer use drastically. Instead, cost‐effective nitrogen abatement includes a mix of various adjustments of farm‐level production practices. The EU set‐aside payment appears to reduce abatement costs.     

An economic interpretation of structural changes in the bovine population of India

Abstract

A computable general equilibrium model based on a social accounting matrix for Kenya is used to simulate the effects of 10% devaluation, 10% increased investment and 10% agricultural productivity improvement on the macro‐economy and on the real incomes of the poor. For each policy simulation two specifications for the labour markets are adopted, the first assuming unlimited supplies of labour at given nominal wages and the second fixed supplies so that wages are determined endogenously. These affect the results crucially. Under the first assumption, devaluation provides a 10% boost to real gross domestic product (GDP) and has highly favourable effects on agricultural production, exports, the current account deficit, employment and poverty. Under the second assumption, it has a largely inflationary impact, with attenuated effects on real GDP and no effect on the current account deficit. Agricultural productivity improvement is less affected by the different specifications and compares favourably with devaluation except for its smaller impact on GDP. The increased investment policy is found to be inferior on most counts. All three policies decrease poverty, though income distribution remains stable.     

A model of shifting cultivation: can soil conservation reduce deforestation?

Shifting cultivators manage soil not only by adjusting soil use on already‐cleared lands, as in continuous cultivation, but also by clearing forests to obtain new fertile soils. This study examines the crucial link between on‐farm soil conservation and deforestation in shifting cultivation by modeling forest clearing as an investment in soil for a private farmer. More generally, by doing so the study attempts to integrate deforestation and soil conservation models which have been separately developed in the literature. Our policy goal is to arrest tropical deforestation—as destruction of global commons—caused by land degradation in shifting cultivation while improving the well‐being of poor shifting cultivators. Our integrated approach enables joint policy analyses of deforestation and land degradation. Three welfare‐enhancing policies are considered. The first is agricultural and nonagricultural subsidies affecting farm and nonfarm income opportunities. The second is fiscal and tenure policies affecting discount rates. Our question is whether the link between forest clearing and soil fertility alters the outcomes of these two standard macroeconomic policies commonly found in the literature. The third policy (or program) is various soil conservation measures affecting soil regeneration and erosivity on already‐cleared lands. This article examines a very important question which has received little attention in previous theoretical works: can soil conservation reduce deforestation? This study confirms anti‐deforestation effects of the promotion of nonfarming activities—a common and often emphasized finding in previous works—among shifting cultivators. More importantly, it also demonstrates that improving various soil conservation measures not only discourages forest clearing among shifting cultivators but also tends to have greater effects on forest protection than promoting nonfarming activities. Contrarily, agricultural price subsidy or technological progress gives rise to the opposite outcome, and lowering the farmer's discount rate or improving tenure security encourages him/her to clear more forests just to accumulate soil.     

Land‐use change trajectories up to 2050: insights from a global agro‐economic model comparison

Changes in agricultural land use have important implications for environmental services. Previous studies of agricultural land‐use futures have been published indicating large uncertainty due to different model assumptions and methodologies. In this article we present a first comprehensive comparison of global agro‐economic models that have harmonized drivers of population, GDP, and biophysical yields. The comparison allows us to ask two research questions: (1) How much cropland will be used under different socioeconomic and climate change scenarios? (2) How can differences in model results be explained? The comparison includes four partial and six general equilibrium models that differ in how they model land supply and amount of potentially available land. We analyze results of two different socioeconomic scenarios and three climate scenarios (one with constant climate). Most models (7 out of 10) project an increase of cropland of 10–25% by 2050 compared to 2005 (under constant climate), but one model projects a decrease. Pasture land expands in some models, which increase the treat on natural vegetation further. Across all models most of the cropland expansion takes place in South America and sub‐Saharan Africa. In general, the strongest differences in model results are related to differences in the costs of land expansion, the endogenous productivity responses, and the assumptions about potential cropland.     

Planning for Agricultural Change and Economic Transformation in Tanzania?

Recently, Tanzania witnessed a revival of economic planning that explicitly aimed to combine rapid economic growth with accelerated structural transformation of the economy. To achieve these planning targets would require a relatively modest drop in the share of agriculture in GDP, but a dramatic fall in its share in employment by 2025. Tanzanian planners assume that labour is locked in agriculture because agricultural productivity is low, from which they conclude that, to release labour to fuel the expansion of manufacturing, it is imperative to raise agricultural productivity by appropriate land policies, leveraging private investment and developing public–private partnerships. We argue that, analytically, this planning argument leaves out the possibility that causality may run the other way – from high labour retention in agriculture to low agricultural productivity – and that, empirically, the observed patterns inherent in actual processes of economic transformation in Tanzania do not tally well with the assumptions of planners. More specifically, in so far as labour flows out of agriculture, it flows towards informal‐sector activities, both rural and urban, rather than towards formal manufacturing.     

Impacts of considering climate variability on investment decisions in Ethiopia

Extreme interannual variability of precipitation within Ethiopia is not uncommon, inducing droughts or floods and often creating serious repercussions on agricultural and nonagricultural commodities. A dynamic climate module is integrated into an economy‐wide model containing a detailed zonal level agricultural structure. This coupled climate‐economic model is used to evaluate the effects of climate variability on prospective irrigation and infrastructure investment strategies, and the ensuing country‐wide economy. The linkages between the dynamic climate module and the economic model are created by the introduction of a climate‐yield factor (CYF), defined at the crop level and varied across Ethiopian zones. Nine sets of variable climate (VC) data are processed by the coupled model, generating stochastic wet and dry shocks, producing an ensemble of potential economic prediction indicators. Analysis of gross domestic product and poverty rate reveal a significant overestimation of the country's future welfare under all investment strategies when climate variability is ignored. The coupled model ensemble is further utilized for risk assessment to guide Ethiopian policy and planning.     

Soil,Striga, or subsidies? Determinants of maize productivity in northern Ghana

High yield gaps persist in sub‐Saharan Africa and increased fertilizer use is considered among the crucial measures to increase productivity. Despite high government investments, particularly in fertilizer subsidy programs (FSPs), overwhelming evidence has revealed their inefficiency. This study employs a multidisciplinary approach to identify the determinants of low maize yields in the Guinea savanna zone of Ghana. We conducted a socioeconomic household survey and analyzed plot‐specific soil samples. Econometric models were estimated based on both socioeconomic and soil variables. The results show that a common parasitic weed, Striga, and labile soil structure have significant effects on yield in the study region. Plot sizes were recorded both from farmers’ direct elicitation and using GPS devices. Considerable discrepancies were detected between self‐reported and GPS‐measured plot sizes. Fertilizer samples from randomly selected agro‐input shops were analyzed to control for adulterated or fake inputs. The measured nutrient contents of the samples reflected the composition indicated on the package labels. Findings underline the need of site‐specific data collection, supported by laboratory‐based soil test results, to efficiently address low productivity. Although there are no signs of fertilizer adulteration, governance challenges persist in targeting, timing, and elite capture in the distribution system of the subsidy program. The study shows that the FSP has not been an effective standalone measure. Rather, the government needs to invest in capacity building and extension services to address the site‐specific problems through comprehensive soil fertility management techniques and weed control. Promoting soil carbon management, minimum mechanical stress, crop rotation, and permanent soil cover should be further investigated as options for the region.     

Nonfarm employment,agricultural intensification,and productivity change: empirical findings from Uganda

This article uses panel data from the Living Standards Measurement Study‐Integrated Surveys on Agriculture for Uganda to assess the farm‐level effects of nonfarm employment on agricultural intensification and productivity change. A sample selection model is used to account for both unobserved heterogeneity and potential simultaneity between agricultural production and nonfarm income. Results show that nonfarm employment can have differential impacts on farm technology intensity and productivity. Nonfarm income is found to have a positive impact on farm hired labor and improved seed intensity; a negative effect on on‐farm family labor use; and no significant impact on fertilizer, soil water management, and joint use of farm technologies. The econometric evidence also indicates that agricultural productivity declines as nonfarm income increases. Taken together, our findings reveal important trade‐offs between nonfarm employment and income and farm productivity growth under smallholder agriculture. The results indicated that targeted policies are required to reduce these potential trade‐offs between nonfarm employment and agricultural intensification and productivity change.     

Investment in soil conservation in northern Ethiopia: the role of land tenure security and public programs

A double hurdle statistical analysis of 250 farms in the Tigray region of Ethiopia reveals different causal factors for soil conservation adoption versus intensity of use. Farmers' reasons for adopting soil conservation measures vary sharply between stone terraces and soil bunds. Long‐term investments in stone terraces were associated with secure land tenure, labour availability, proximity to the farmstead and learning opportunities via the existence of local food‐for‐work (FFW) projects. By contrast, short‐term investments in soil bunds were strongly linked to insecure land tenure and the absence of local food‐for‐work projects. Public conservation campaigns on private plots reduced adoption of both stone terraces and soil bunds. Whereas capacity factors largely influenced the adoption decision, expected returns carried more influence for the intensity of stone terrace adoption (measured as metres of terrace per hectare). More stone terracing was built where fertile but erodible silty soils in higher rainfall areas offered valuable yield benefits. Intensity of terracing was also greater in remote villages where limited off‐farm employment opportunities reduced construction costs. These results highlight the importance of the right kind of public interventions. Direct public involvement in constructing soil conservation structures on private lands appears to undermine incentives for private conservation investments. When done on public lands, however, public conservation activities may encourage private soil conservation by example. Secure land tenure rights clearly reinforce private incentives to make long‐term investments in soil conservation.     

Foreign Direct Investment and the Performance of European Agribusiness Firms

This article analyses the relationship between foreign direct investment and the performance of European agribusiness firms. Motivated by the role of heterogeneous firms in new trade theory and using a firm‐level dataset, statistical analyses identify key differences between firms investing in foreign economies and those that do not. A binary choice model quantifies the relationship between firm characteristics and the decision to engage in foreign investment. Size and – less strongly – productivity are greater for multinationals relative to domestic firms. Furthermore, European multinationals are characterised by a larger debt to equity ratio and show lower labour and input costs.