Risky Crop Research Articles

Paddy-based Cropping Systems and their Sustainability: A Micro-level Study of Nellore District of Andhra Pradesh, India

A sustainable cropping system is needed to ensure profitable, productive and less risky crop production, particularly when the agricultural sector is experiencing climatic uncertainty and price volatility. Hence, the study aims to identify paddy-based cropping systems and their sustainability in the Nellore district of Andhra Pradesh. The study is based on primary data collected during 2022-23 with the help of a pre-structured schedule. The major cropping systems based on paddy were identified as system Ⅰ (paddy-groundnut), cropping system Ⅱ (paddy-paddy), & cropping system Ⅲ (paddy-cotton). The profitability analysis revealed that the gross returns for cropping systems I, II and III were computed to be Rs. 281916.83, Rs. 259072.90 and Rs. 330072.45. The farmers realized the highest net income, Rs. 169222.62, under cropping system III. The net returns for the cropping systems Ⅰ and Ⅱ were obtained as Rs. 141282.24 and Rs. 127048.48, respectively. The sustainability indices of paddy-groundnut (cropping system I), paddy-paddy (cropping system II) and cropping system III (paddy-cotton) were computed as 42.88%, 50.86% and 60.93%, respectively, and the paddy-cotton cropping system came out as the most profitable and sustainable in the study area. The regression analysis revealed that factors like returns to cost ratio and the cost used for environmentally friendly inputs relative to the overall cost of cultivation were found significant in all three cropping systems.

Extreme heat and rural household adaptation: Evidence from Northeast China

More extreme heat events are expected under climate change, posing threats to food production as well as the lives of agriculture-dependent rural households. Using a detailed panel of rural households in an agricultural region of China, we find extreme heat substantially decreases crop production and lowers households’ agricultural returns. Nevertheless, the households successfully smooth their consumption contemporaneously by utilizing precautionarily saved buffers (liquid financial assets and crop stocks), especially among those who regularly hold these buffers. Their future expenditures are also largely unaffected. This adaptability of consumption smoothing discourages within-season adjustments in variable inputs and productive assets. Still, extreme heat guides impacted households toward a more diverse but less risky crop portfolio in later years.

APSIM next generation mungbean model: A tool for advancing mungbean production

Mungbean, a grain legume with high nutritional value, is grown widely throughout Asia and increasingly in Australia. Despite growing interest amongst farmers, mungbean remains an inconsistent and thus risky crop to plant in Australia. Cropping system models like the Agricultural Production Systems sIMulator (APSIM) are valuable tools for helping farmers to examine options for improving crop management and assess production risks across potential growing regions for mungbean. This paper outlines the simulation capacity of a new mungbean crop model parameterized using the Plant Modelling Framework in APSIM Next Generation, the newest version of the APSIM framework. The aim of the paper is to document the parameterization and validation processes of the model. The new mungbean model was built using data from 28 field experiments to simulate measured phenology, canopy development, biomass accumulation/partitioning, stress responses, N fixation, root growth, and yield across a wide range of environments. The root mean squared error (RMSE) in predictions for grain weight and aboveground weight were 25.4 g m−2 and 91.4 g m−2, respectively. The model successfully captured the dynamics of crop response to sowing dates, water/irrigation regimes, and climate. The new mungbean model is a robust and accurate tool for use in Australia and tropical/sub-tropical Asia. Researchers can use the new mungbean model to determine best management practices such as the optimal time to sow mungbeans in different environments. The output from model simulations can help farmers assess risks associated with sowing at different times and soil water conditions specific to their region. Such risk analysis can improve farmer decision-making confidence in mungbean, increasing its potential production for Australia. Overall, the new APSIM mungbean model can be used effectively to identify and close the mungbean yield gap, mitigate risk of crop failure, and increase profits for mungbean farmers in Australia and tropical/sub-tropical Asia; it has the capacity to assist with increasing mungbean production globally under changing climate conditions.

Risk Epistemologies and Aesthetic Reflexivity of a Disaster-Affected Community: Findings from Vietnam

Scholars and policymakers often use their expert knowledge to define the risk that laypeople face. Nonetheless, they have frequently overlooked how laypeople describe and explain the risks they face on a daily basis. Moreover, an emphasis on individualisation and reflexivity in Western societies has led to little understanding of how a non-Western community constructs its shared risk culture and how this culture associates aesthetic reflexivity and risk epistemologies. The purpose of this research is to fill these gaps by exploring how Vietnamese farmers reflexively define risk in their everyday lives, which in turn informs their risk-taking attitude and action. Drawing on a case study of disaster-prone farmers in the Vietnamese Mekong Delta, this research reveals a distinct set of farmers’ risk epistemologies through a process of hermeneutic reflexivity situated in their risk culture and a shared identity. They do not view risk as wholly negative but rather as an opportunity to attain the aim of surviving and profiting. They see cultivating a risky crop as a collective action of risking their lives, sharing with their community both the challenges and the opportunities that risk might offer. My article makes a case for sociological research into non-Western civilizations, where late modernity and reflexivity might not be accompanied by individualisation but rather with collectivism and tradition.

The effect of nitrogen-fertilizer and optimal plant population on the profitability of maize plots in the Wami River sub-basin, Tanzania: A bio-economic simulation approach

Maize (Zea mays L.) is the essential staple in sub-Saharan Africa (SSA) and Tanzania in particular; the crop accounts for over 30% of the food production, 20% of the agricultural gross domestic product (GDP) and over 75% of the cereal consumption. Maize is grown under a higher risk of failure due to the over-dependence rain-fed farming system resulting in low income and food insecurity among maize-based farmers. However, many practices, including conservation agriculture, soil and water conservation, resilient crop varieties, and soil fertility management, are suggested to increase cereal productivity in Tanzania. Improving planting density, and the use of fertilizers are the immediate options recommended by Tanzania's government. In this paper, we evaluate the economic feasibility of the improved planting density (optimized plant population) and N-fertilizer crop management practices on maize net returns in semi-arid and sub-humid agro-ecological zones in the Wami River sub-Basin, Tanzania. We introduce a bio-economic simulation model using Monte Carlo simulation procedures to evaluate the economic viability of risky crop management practices so that the decision-maker can make better management decisions. The study utilizes maize yield data sets from two biophysical cropping system models, namely the APSIM and DSSAT. A total of 83 plots for the semi-arid and 85 plots for the sub-humid agro-ecological zones consisted of this analysis. The crop management practices under study comprise the application of 40 kg N-fertilizer/ha and plant population of 3.3 plants/m2. The study finds that the use of improved plant population had the lowest annual net return with fertilizer application fetching the highest return. The two crop models demonstrated a zero probability of negative net returns for farms using fertilizer rates of 40 kg N/ha except for DSSAT, which observed a small probability (0.4%) in the sub-humid area. The optimized plant population presented 16.4% to 26.6% probability of negatives net returns for semi-arid and 14.6% to 30.2% probability of negative net returns for sub-humid zones. The results suggest that the application of fertilizer practices reduces the risks associated with the mean returns, but increasing the plant population has a high probability of economic failure, particularly in the sub-humid zone. Maize sub-sector in Tanzania is projected to continue experiencing a significant decrease in yields and net returns, but there is a high chance that it will be better-off if proper alternatives are employed. Similar studies are needed to explore the potential of interventions highlighted in the ACRP for better decision-making.

Climate risk, vulnerability and resilience: Supporting livelihood of smallholders in semiarid India

Using panel data from 256 smallholder households from 2006 to 2014 in three semiarid regions India, this study develops a framework for quantifying vulnerability and resilience by accounting for a smallholder household’s ability to adapt and respond to climatic risk. Findings indicate that although smallholders with smaller landholdings are more vulnerable to climatic risk (drought, in our case), they are also more resilient than their counterparts. Results reveal that cropping intensity and crop risk increase the vulnerability of smallholders to climatic risk, but large farms are less vulnerable. Diversification in on-farm enterprises, like livestock units, and off-farm income sources, play significant roles in increasing smallholder households’ resilience to climatic risk. Other drivers of resiliency include the choice of cash and risky crops, borrowing capacity, liquid investments, and the ability to regain yields.

Conflict-Risk and Agricultural Portfolios: Evidence from Northern Uganda

Although the impact of insecurity on agricultural decisions is widely discussed, it remains largely unstudied empirically. This study estimates the effect of risk of violence on livestock and crop portfolios using spatially disaggregated risk measures and data from over 690,000 households, approximately 75 per cent of all rural households in Northern Uganda. As the risk of violence increases, households decrease their livestock holdings while shifting its composition towards smaller, less risky animals that can be kept within villages. The similarly strong shifts in the choice of crops, however, are not always consistent with a shift towards less risky crops. Since households remain reliant on agriculture, these ex ante behavioural responses to insecurity suggest important consequences for welfare.

Effects of subsidized crop insurance on crop choices

AbstractThis study focuses on how subsidized crop insurance affects crop choices. Crop insurance may change farm investments by reducing risks and providing subsidies. First, actuarially fair insurance reduces risks in crop production and marketing, holding the expected return constant. Second, insurance subsidies encourage farms to purchase crop insurance, which increases the expected return to insured risky crops. Farms also have many self‐insurance mechanisms such as crop diversification or working off the farm. We derive conditions under which (1) unsubsidized and actuarially fair crop insurance or (2) insurance premium subsidies lead to more investment in a risky higher return crop. We then examine the role of self‐insurance for these conditions. The impact of premium subsidies is decomposed into a direct profit effect and an indirect coverage effect. These effects are explained by substitutions between market insurance and self‐insurance and between a risky crop and a safe crop. We discuss each effect as a combination of subsidy and risk effects. Numerical illustrations show that an insurance subsidy has a larger impact on risky crop investments compared to that of an input subsidy when farms are more risk‐averse and have high costs of self‐insurance. The framework provides a novel way to evaluate subsidized crop insurance programs.

Determinants of yield and quality in winter rapeseed (Brassica napus L.) under Mediterranean conditions

SUMMARYWinter rapeseed was introduced into Greece a decade ago to provide oil for biodiesel. To identify agronomic traits affecting yield and quality, three hybrids and an inbred line were tested over two seasons (2005–2006 and 2006–2007) and four locations, in central and northern Greece, varying in pedo-climatic conditions. The large variations in seed yield, quality and agronomic traits were largely ascribed to location; in contrast, cultivar accounted for ⩽0·010 of the variation for many traits. Below 40°N, rapeseed is a risky crop; short season, high temperatures and low rainfall during reproductive growth diminished seed yield and oil content, increased oleic and erucic acid and minimized linolenic acid. A hybrid, Exact, with tall stature and large seeds was adaptive to such conditions. The most productive location had dense stands with tall plants bearing numerous pods on the main raceme. At the site with the coldest winter, plant density (PD) was lowest (ca. 30 plants/m2) but rapeseed compensated by producing large seeds, with high oil content and harvest index (HI). A biplot revealed that the hybrid Excalibur, outperforming the other cultivars for oil content in six out of eight trials, produced the highest and most stable oil yield. Combined data showed that seed yield and oil yield were positively correlated with PD, seed size and HI and negatively to the number of pods on branches and per plant. Large seeds had high seed oil content. Oleic acid was negatively correlated to linolenic acid concentration. High temperatures and low rainfall favoured oleic acid, which was positively associated with seed number per pod.

A methodology for multi-objective cropping system design based on simulations. Application to weed management

Abstract Weeds are harmful for crop production but important for biodiversity. In order to design cropping systems that reconcile crop production and biodiversity, we need tools and methods to help farmers to deal with this issue. Here, we developed a novel method for multi-objective cropping system design aimed at scientists and technical institutes, combining a cropping system database, decision trees, the “virtual field” model F lor S ys and indicators translating simulated weed floras into scores in terms of weed harmfulness (e.g. crop yield loss, weed-borne parasite risk, field infestation), weed-mediated biodiversity (e.g. food offer for bees) and herbicide use intensity. 255 existing cropping systems were simulated with F lor S ys , individual indicator values were aggregated into a multi-performance score, and decision trees were built to identify combinations of management practices and probabilities for reaching performance goals. These trees are used to identify the characteristics of existing cropping systems that must be changed to achieve the chosen performance goals, depending on the user's risk strategy. Alternative systems are built and simulated with F lor S ys to evaluate their multi-criteria performance. The method was applied to an existing oilseed rape/wheat/barley rotation with yearly mouldboard ploughing from Burgundy which was improved to reconcile weed harmfulness control, reduced herbicide use and biodiversity promotion, based on a risk-minimizing strategy. The best alternative replaced a herbicide entering plants via shoot tips (during emergence) and roots after barley sowing by a spring herbicide entering via leaves, introduced crop residue shredding before cereals and rolled the soil at sowing, which reduced the risk of unacceptable performance from 90% to 40%. When attempting to reconcile harmfulness control and reduced herbicide use, the best alternative changed the rotation to oilseed rape/wheat/spring pea/wheat, replaced one herbicide in oilseed rape by mechanical weeding, delayed tillage before rape and applied the PRE herbicide before oilseed rape closer to sowing. This option reduced the risk of unacceptable performance to 30%. None of the initial or alternative cropping systems succeeded in optimal performance, indicating that more diverse cropping systems with innovative management techniques and innovative combinations of techniques are needed to build the decision trees. This approach can be used in workshops with extension services and farmers in order to design cropping systems. Compared to expert-based design, it has the advantage to go beyond well-known options (e.g. plough before risky crops) to identify unconventional options, with a particular focus on interactions between cultural techniques.

Determine optimal crop planning under conditions of water risk in Namakkal district of Tamil Nadu

Water is a critical input for success of agriculture and its ever widening technology creation. Water scarcity as a risk has always been a part of agriculture and farm business. Hence, management of available irrigation water assumes great importance in the field of agriculture. The present study was attempted in Namakkal district of Tamil Nadu, India, because of the availability of exclusive dry farms. In Namakkal district, blocks namely Namakkal, Mohanur, Pudhuchatram, Tiruchengode for each risky crop were purposively selected on the basis of area, production and productivity of those crops. Linear programming model was applied to derive optimal crop plan for the sample farms under water stress conditions. Optimization of crop portfolio for the selected farm is a type of risk management strategy. The decline in gross cropped area in Namakkal block would imply relatively less pressure on land that would again indicate the sign of bringing in sustainability of the productive capacity of the land. Even though the decline trend in net income, it showed that the resources which were used in the cultivation as efficiency factor in Pudhuchatram. The results indicated that water and other resources were used efficiently to get optimum pattern in the cultivation of different crops.

Guidelines of Sustainable Soil Tillage System in Croatia (Contribution to Sustainable Land Management in 2015 - International Year of Soils)

Within soil degradation processes soil erosion is on the first place, as consequence of improper land man-agement, first of all soil tillage system and practices. Results of 10 years (1995-2004) of our investigation (investigation endure now 21st year) show guidelines in tillage practices. At first; traditional tillage practiced in this agricultural region up/down the slope on Stagnogley on slopes of 9 % and more is unsustainable in growing of row crops-maize and soybean, because of disastrous or extreme soil erosion. But, in growing of crops of high density, like wheat this practice is sustainable. On the other side, No-tillage and contour tillage resulted in much lower water erosion in comparison with up/down the slope tillage. At the beginning of experiment in the first two years No-tillage as system was not sustainable. Stabilization of yields of growing crops on the level which is statistically the same or higher than on other tillage treatments on notillage plot started after ten years of no-tillage practice. These investigations suggest the conclusion that high density crops like winter wheat, spring barley and oilseed rape are relatively suitable crops for growing under reduced tillage systems. Soybean tolerates no-till practices in climatically favourable years, but with higher risk in dry years. Maize was shown as a very risky crop without tillage even in climatically average years. We agree with assertion of Solbrig [1] that no tillage is a process, a new philosophy and way of thinking in arable farming of Europe, and not a technology.

Quantifying the sources of revenue variation in the Northern Great Plains

Purpose – The purpose of this paper is to determine the sources and factors affecting farm revenue variation on crop and livestock farms in the Northern Great Plains. Design/methodology/approach – A two method approach is used. Variance decomposition analysis is completed on an 18-year balanced panel data set of North Dakota producers to determine the sources of farm revenue variation. The second component of this research uses a random effects estimator to determine the effect of farm characteristics on farm revenue variation measured by coefficient of variation. Findings – Crop revenue is the largest source of farm revenue variation, with crop insurance being the largest source of revenue variation diversification. Small market crops and corn were found to increase revenue variation compared to those operations that received the largest sum of their revenue from wheat. Government payments and insurance payments were also found to increase farm revenue variation indicating they may provide an incentive to plant more risky crops. Originality/value – This analysis examined specific enterprises that affect farm revenue variation, which has not been examined in earlier work. This distinction allows for focus on potential policy implications of small market crops and new crops in “transitional planting zones”.

Rainfall variability and food crop portfolio choice: evidence from Ethiopia

This paper concerns the patterns of food crop choice in a multicropping setting, in which production risk considerations and rainfall uncertainty are likely to be critical factors. The analysis employed plot level panel data from Ethiopia, combined with 30 year meteorological data corresponding to the survey villages used to construct seasonal and yearly rainfall variability. Using the single index approach, the riskiness of crop portfolio was constructed at a household level, taking into account the multicropping nature of the farming system. The combined riskiness of crops grown at a household level responded negatively to annual rainfall variability, with seasonal rainfall variability having a less consistent impact. Farmers are, therefore, more likely to select less risky crop portfolios even when intercrop interactions are taken into account.

Yield and water productivity of Bt cotton (Gossypium hirsutum) as influenced by temperature under semi-arid conditions of north-western India: field and simulation study

Cotton cultivation in semi-arid region of Indian Punjab is considered as most risky crop as its yield is very sensitive to weather parameters like rain and temperature. In future due to global warming increase in the temperature is expected, which is most likely to influence the growth and yield of this fiber crop like other cereal crops. Studies on the effect of temperature on the growth and seed yield of Bt cotton in this region are lacking. The present 2-year field and 15-year simulation studies concern to simulate the effect of temperature on duration of pheno-phases and seed yield of Bt cotton hybrid RCH 134 and also on crop water productivity. Simulations were run for 15 years (1991–2005) using the already customized CropSyst model. The simulated results indicated that with increase in temperature from 28 to 32oC, cotton seed yield was reduced to half (from 4 700 to 2 300 kg/ha) following a linear relation with high coefficient of determination (0.97), and the reduction was more with increased temperature during sowing to flowering stage than other pheno-phases. Total evapo-transpiration (ET) during crop period and crop water productivity was also decreased with increased temperature. Relationship of cotton seed yield was linear with ET and quadratic with total water supply (rain +irrigation). Real crop water productivity (yield/ET) and apparent crop water productivity (yield/irrigation water) were 0.362+0.129 and 0.485+0.120 kg/m3, respectively.

Household Decision-Making Under Threat of Violence: A Micro Level Study in the Chittagong Hill Tracts of Bangladesh

We analyze rural household livelihood and children’s educational investment decisions in a post-conflict setting located in the Chittagong Hill Tracts region of Bangladesh. The study represents a contribution to the microeconomic analysis of conflict. Another innovation of the paper lies in the fact that we employ information about subjective perceptions of violent experiences, which is in turn used to explain household economic decision making. Heightened subjective perceptions of violence lower consumption expenditure, but it can raise land use intensity, and more risky mixed crop cultivation. In some case experiences of displacement and other violence raises the likelihood of households sending children to school. This indicates that a specific post-conflict ‘phoenix’ factor may be in operation, even without substantial infrastructure reconstruction. Also, the trauma emanating from actual past experiences combined with current high perceptions of risk of violence after an imperfect accord ending a low-intensity conflict may make people bolder and more risk taking in order to enhance their long-term future. We, therefore, also make a contribution to the literature on a non-linear relationship between violence and the temporal patterning of livelihood decision-making.

Mathematical modeling of the South African land redistribution for development policy

The ineffectiveness of policy advice in most African countries could be attributed, amongst others, to the problem of scientists not being able to present or communicate a holistic solutions to policy challenges. As a result, the potential and actual consequences of policies are seldom indicated. It may be demanding to use a more comprehensive and quantitative research method in policy analysis because of limited resources to integrate technical, biophysical with the socio-economic and political variables when analysing policy effects. To exemplify this phenomenon, a forward-looking and prescriptive economic analysis that is being widely used for ex-ante policy analyses was used to make a contribution to the discussion on land redistribution, which is presently not only one of the most definitive political and development issues, but perhaps the most intractable in South Africa. The study develops and uses a mathematical model for regionalised farm-level resource use and output supply response to show that the current policy requires more economic imperatives, as it tends towards smallholder agriculture that has elements of low capital threshold trap. After 30% of the farmland will have been transferred from the large farm type to settle more units of small farm type by 2015, the decrease in the number of large farm units from about 8531 units in the base year to about 7112 farm units will lead to a decline in crop and animal product supplies. Such declines (about 15.3%) will overwhelm the increase of more than 1600% in supplies as a result of increased small farm units. Given the challenges of a free market and the fact that the current farm settlement arrangement lacks appreciable efficiency, the study prescribes land redistribution strategies that consider efficiency along with equity. Taking size as an indication of efficiency, an increase in technical progress at 1, 5 and 10% is expected to shift the supply curves to the right for less risky crop and animal enterprises meaning having more farmland, which may imply reduced lack of capital constraints would not necessarily imply a general increase in all the production activities because of relative risks in revenues. The study however, suggests that agricultural land can act as a safety net for the poor, where the efficiency argument does not hold.

A quadratic application in farm planning under uncertainty

Farming in Bangladesh is confronted with various types of uncertainties, which contribute to farmers’ income volatility over the years. As a result, cereal, mainly rice, which is a less riskier crop remained dominantly planted in the current farm plan. But the return generated from rice cultivation has not been able to improve the livelihood of the poor, as rice profitability is low compared to some profitable but risky crops like jute and vegetables. To investigate the behavioral pattern of the farmers towards risk, Dhaka division, largely known as central region of Bangladesh, is selected. The prevailing farm plan of Dhaka division is compared with the efficient one at the current level of expected return in order to check whether the current farm plan is risky or otherwise. Quadratic and MOTAD as well as linear programming techniques have been employed for the analysis. The result of the study reveals that the prevailing farm plan in Dhaka division is risky compared to the efficient plan. Since the current return level is low, the study has recommended that more jute and vegetables should be planted to achieve higher remuneration.

Quantification of Grain Yield Response to Soil Depth in Soybean, Maize, Sunflower, and Wheat

Risk analysis to identify the more profitable or less risky crops in areas with shallow soil requires quantification of yield responses to physical constraints to root penetration. Grain yield, shoot biomass, and harvest index (HI) were measured in commercial fields of indeterminate soybean (Glycine max L. Merr.), maize (Zea mays L.), sunflower (Helianthus annuus L.), and wheat (Triticum aestivum L.) grown on Typic Argiudols and Petrocalcic Paleudols. At crop maturity, shoots were sampled along transects (approximately 200 m) with soil depths between 0.35 and >1 m as determined by petrocalcic horizon depth. In all four species, shallow soil reduced shoot biomass and grain yield but did not affect HI in wheat. Harvest index was most affected by shallow soil in maize. Seasonal water deficit [maximum – actual evapotranspiration (ET)] accounted for 43 to 90% of the variation in yield. Average water use efficiency (WUE) was wheat, 14.5; maize, 11.7; soybean, 8.9; and sunflower, 7.5 kg grain ha−1 mm−1 ET. In relation to crops on the deepest soil, yield decline per centimeter reduction in soil depth was 0.41% in wheat, 0.45% in soybean, 0.54% in sunflower, and 0.76% in maize. This ranking of grain yield response to shallow soil was mostly accounted for by (i) cropping season (autumn to late spring for wheat vs. spring to autumn for row crops), (ii) timing of the most critical period for grain yield determination (later in soybean than in sunflower and maize), and (iii) plant features related to vegetative and reproductive plasticity, including growth habit.

Agroforestry, attitude towards risk and nutrient availability: a case study of south Indian farming systems

Introduction of two systems of agroforestry to the farmers portfolio is evaluated for their changes in cropping pattern, input use, income generation, farmers attitude towards risk and nutrient availability. Two different types of farmers are studied under both irrigated and dryland farming systems. Farm survey data collected from south Indian villages have been used with a mean-variance framework to identify the risk aversion levels of farmers. The results indicate that the risk-taking preferences of farmers should be given consideration in evaluating the impact of agroforestry systems. Among the two agroforestry systems analyzed, the one with drumstick is shown to increase the risk of crop production while the one with leucaena reduces the risk and enables farmers to invest in more risky cash crops. The impact of agroforestry on crop allocation, input use and income differs due to the differences in resource availability of farmers. The influence of agroforestry on nutrient availability of the farm households also differs based on the components of agroforestry, orientation of farming and the nature of farming systems. It is argued that design of agroforestry systems should consider differences in resource constraints in farming systems and risk attitudes of farmers towards their allocation decisions and that such considerations would largely enhance the successful adoption of agroforestry in developing countries.