Gains from crop diversification in the Sudan Gezira scheme

Land allocation in Gezira irrigation scheme (the Gezira) has, for the most part, been based on the political judgement of the government rather than economic criteria. This paper determined optimum crop combinations for the Gezira using the mean-variance (M-V) model. This large-scale gravity-irrigated project which was started for export cotton cultivation on 27,372 feddan (11,496 ha) in 1927 has now expanded to over two million feddan, and has a multi crop production system. Sources of production uncertainty include government control of prices, often announced after planting, and crop area in favor of cotton. Diversification was analyzed under various levels of risk using, in contrast to what is in the reviewed literature, both cross sectional and time series farm level data. The cross-sectional data comprised of net farm returns of 100 farmers for the 1987/1988 season, and the time series data were average net farm returns from the same area from 1971 to 1988. Cropping decisions in the Gezira are mostly based on cross-sectional data from a sample of tenants in the preceding season. This paper estimated variance and covariance parameters of observed net margins of both sets of data and found significant differences in the results. The certainty equivalence results used to evaluate crop diversification showed that current policies of controlling crop acreage lead to inefficient land use; and that farmers diversify into wheat and groundnuts out of cotton when cross-section data were used; and from groundnuts to cotton and wheat when time series data were used.     

Management planning for winter wheat with multiple objectives (1): The BETHA system

Today, farmers have to fulfil the economic, technological and environmental requirements laid down by agro-industries or consumers, or government regulations. This makes designing crop management plans more complex. A tool specific for a wheat crop has therefore been devised: the BETHA system. First, BETHA generates feasible crop management plans from an agronomic model. This agronomic model includes simple relationships that link qualitative and quantitative production to the crop, the crop techniques and climate and soil characteristics. As BETHA is a knowledge-based system, the user can easily modify the agronomic model. BETHA then performs a multiple criteria analysis to classify the crop management plans according to their capacity to follow the competing requirements defined by the user. A non-totally compensatory method based on agreement and discordance principles has been used because these criteria may be very different and cannot be directly aggregated.     

Changing patterns of water distribution under the influence of land reforms and simultaneous WUA establishment

In 2005 the Uzbek government accelerated the dissolution process of collective farms through full-scale land reform. As the central production unit, the collective enterprise was supplanted by a private, family-based enterprise. Simultaneously Water Users Associations (WUAs) were established that operate and maintain the irrigation and drainage infrastructure of the former collective farms. Though these land-cum-water reforms could in principle initiate enormous changes, there is still a strong continuity due to the state-regulated agricultural system. Although officially only cotton and wheat production are still subject to a state order system, the whole agricultural production is still under strict state control. This paper builds on research conducted during the spring and summer of 2005 and 2006 in the oasis of Khorezm, Uzbekistan. Through field walks in combination with semi- and non-structured interviews, two cases of water management at former collective farm (FCF) level were distinguished: one at the onset of reform and one two years after full-scale reforms. The former shows the strong interlinkage at FCF level between the control of agricultural production and water management. However, the second case shows that even in the post-reform context, where the co-ordination of production and the control of cropping areas are formally no longer arranged at this level, these functions are informally reproduced through the new institutions. The WUA forms a crucial link between privatised producers and a state preoccupied with control.     

Water productivity analysis of irrigated crops in Sirsa district,India

Water productivity (WP) expresses the value or benefit derived from the use of water, and includes essential aspects of water management such as production for arid and semi-arid regions. A profound WP analysis was carried out at five selected farmer fields (two for wheat–rice and three for wheat–cotton) in Sirsa district, India during the agricultural year 2001–02. The ecohydrological soil–water–atmosphere–plant (SWAP) model, including detailed crop simulations in combination with field observations, was used to determine the required hydrological variables such as transpiration, evapotranspiration and percolation, and biophysical variables such as dry matter or grain yields. The use of observed soil moisture and salinity profiles was found successful to determine indirectly the soil hydraulic parameters through inverse modelling.Considerable spatial variation in WP values was observed not only for different crops but also for the same crop. For instance, the WP_ET, expressed in terms of crop grain (or seed) yield per unit amount of evapotranspiration, varied from 1.22 to 1.56 kg m⁻³ for wheat among different farmer fields. The corresponding value for cotton varied from 0.09 to 0.31 kg m⁻³. This indicates a considerable variation and scope for improvements in water productivity. The average WP_ET (kg m⁻³) was 1.39 for wheat, 0.94 for rice and 0.23 for cotton, and corresponds to average values for the climatic and growing conditions in Northwest India. Including percolation in the analysis, i.e. crop grain (or seed) yield per unit amount of evapotranspiration plus percolation, resulted in average WP_ETQ (kg m⁻³) values of 1.04 for wheat, 0.84 for rice and 0.21 for cotton. Factors responsible for low WP include the relative high amount of evaporation into evapotranspiration especially for rice, and percolation from field irrigations. Improving agronomic practices such as aerobic rice cultivation and soil mulching will reduce this non-beneficial loss of water through evaporation, and subsequently will improve the WP_ET at field scale. For wheat, the simulated water and salt limited yields were 20–60% higher than measured yields, and suggest substantial nutrition, pest, disease and/or weed stresses. Improved crop management in terms of timely sowing, optimum nutrient supply, and better pest, disease and weed control for wheat will multiply its WP_ET by a factor of 1.5! Moreover, severe water stress was observed on cotton (relative transpiration < 0.65) during the kharif (summer) season, which resulted in 1.4–3.3 times lower water and salt limited yields compared with simulated potential yields. Benefits in terms of increased cotton yields and improved water productivity will be gained by ensuring irrigation supply at cotton fields, especially during the dry years.     

Modeling irrigated cotton with shallow groundwater in the Aral Sea Basin of Uzbekistan: I. Water dynamics

In Khorezm, a region located in the Aral Sea basin of Uzbekistan, water use for irrigation of predominantly cotton is high whereas water use efficiency is low. To quantify the seasonal water and salt balance, water application, crop growth, soil water, and groundwater dynamics were studied on a sandy, sandy loam and loamy cotton field in the years 2003 and 2005. To simulate and quantify improved management strategies and update irrigation standards, the soil water model Hydrus-1D was applied. Results showed that shallow groundwater contributed a substantial share (up to 399 mm) to actual evapotranspiration of cotton (estimated at 488–727 mm), which alleviated water stress in response to suboptimal quantities of water applied for irrigation, but enhanced concurrently secondary soil salinization. Thus, pre-season salt leaching becomes a necessity. Nevertheless, as long as farmers face high uncertainty in irrigation water supply, maintaining shallow groundwater tables can be considered as a safety-net against unreliable water delivery. Simulations showed that in 2003 around 200 mm would have been sufficient during pre-season leaching, whereas up to 300 mm of water was applied in reality amounting to an overuse of almost 33%. Using some of this water during the irrigation season would have alleviated season crop-water stress such as in June 2003. Management strategy analyses revealed that crop water uptake would only marginally benefit from a permanent crop residue layer, often recommended as part of conservation agriculture. Such a mulch layer, however, would substantially reduce soil evaporation, capillary rise of groundwater, and consequently secondary soil salinization. The simulations furthermore demonstrated that not relying on the contribution of shallow groundwater to satisfy crop water demand is possible by implementing timely and soil-specific irrigation scheduling. Water use would then not be higher than the current Uzbek irrigation standards. It is argued that if furrow irrigation is to be continued, pure sandy soils, which constitute <5% of the agricultural soils in Khorezm, are best to be taken out of annual cotton production.     

春小麦高产叶龄模式的研究

本研究根据春小麦的叶龄进程，对水、肥、密等影响产量的主要因素进行优化组合，提出了旨在提高春小麦的产量及获得最佳效益的高产模式，为指导我国北方春小麦的生产提供了科学依据。     

Economic potential for soil carbon sequestration in the Nioro region of Senegal’s Peanut Basin

This paper presents results from an analysis of the economic potential for soil carbon sequestration in the Nioro region of Senegal’s Peanut Basin. This analysis was based on the linkage of site-specific biophysical models and economic simulation models using the Tradeoff Analysis System to simulate farmers’ participation in contracts to sequester soil carbon. Available soils and climate data were used to implement the DSSAT/Century models to estimate crop yields and changes in soil carbon stocks under nine scenarios of increased fertilizer use and increased incorporation of crop residues in a peanut-millet rotation. Data from the 2001 farm survey conducted by the Ecole Nationale d’Economie Appliquée were used to parameterize a spatially explicit econometric-process simulation model for the peanut-millet production system. The economic simulation model was used to simulate a carbon-payment scheme that requires farmers to apply higher fertilizer rates and incorporate some crop residues into the soil. The results show that the combination of increased fertilizer use and crop residue incorporation could result in the supply of marketable quantities of carbon that could be sequestered in the soils of the Nioro region. However, the sensitivity of results to the levels of labor costs of incorporating crop residues, the value of crop residues, and the transaction costs of implementing carbon payment schemes, suggests the need for better data on these variables and for an accurate assessment of the capabilities of local institutions to implement carbon contracts.     

An alternative water source and combined agronomic practices for cotton irrigation in coastal saline soils

The field experiment for cotton crop (Gossypium hirsutum L.) was conducted at the Zhongjie Farm, Huanghua city of Hebei province in the coastal salinity-affected areas in North China Plain, to determine the effects of an alternative of irrigation water sources/methods and agronomic practices on seedling emergence and yields of cotton, soil water–salt distributions, and soil pH changes during cotton growth stages. The experiment was setup using split-plot design with two water sources as main treatments (well water/desalinized sea-ice water); two irrigation methods (+PAM (Polyacrylamide)/−PAM); and four fertilization modes: check (CK), mineral fertilizer (F), mineral + organic fertilizer (FM), and mineral fertilizer + gypsum (FG). Using desalinized sea-ice water irrigation showed the same effects on top-soil salt leaching and desalinization as using well water did. There was no significant difference in seedling emergence and cotton yields between two irrigation water sources for cotton irrigation. Using PAM-treated irrigation, the 10-cm top-soil salinity significantly decreased to about 2.3–3.9 g kg⁻¹ from 4.6 to 8.6 g kg⁻¹ (PAM untreated). The PAM-treated irrigation increased seedling emergence by about 13, 29 and 36% and yields by about 50, 49, and 70%, with F, FM, and FG, respectively, as compared with CK. PAM-treated irrigation, either using well water or desalinized sea ice, especially in combination with gypsum-fertilization, shows the best practice for both seedling emergence and cotton yields. In conclusion, the desalinized sea-ice water used as an alternative water source, integrated with better agronomic practices of soil water-salt management could be acceptable for cotton irrigation in the coastal saline areas.     

Agronomic and gross margin analysis of an insect pest suppressive broccoli cropping system

The current reliance on insecticides in broccoli production systems has resulted in consumer concerns in relation to chemical residues, quality assurance issues and pest control failures. An alternative to conventional production methods has been shown to reduce insecticide requirements, however the economic feasibility of the new system needs to be considered to facilitate adoption by farmers. Therefore, the agronomic and economic performance of an insect pest suppressive broccoli and cereal rye cover crop system was compared to a broccoli strip crop system and conventional practice (broccoli monoculture). The broccoli cover cropping system resulted in fewer leaves, smaller plants and a slightly reduced yield when compared to the other systems. Strip cropping broccoli with potatoes did not convey any agronomic advantages. Gross margin analysis revealed that on a total system basis, a 2.2% yield improvement or a 7% price premium was required to make the cover crop system perform as well as conventional practice.     

A rule-based method for the development of crop management systems applied to grain sorghum in south-western France

A generic approach is proposed for the development and testing of crop management systems in contrasting situations of water availability. Ecophysiological knowledge, expertise, regional references and simulation models are combined to devise management strategies adapted to production targets and constraints. The next stage consists of converting these crop management strategies into logical and consistent sets of decision rules. Each rule describes the reasoning which is used to apply a technical decision by taking account of observed or simulated environmental conditions or predicted agronomic risks.

This approach was applied to design crop management systems for grain sorghum (Sorghum bicolor L. Moench.) in south-western France. For spring-sown crops, management (sowing date, plant density, varietal choice, N fertilizer rate and timing) was based on water availability, both for economic and environmental reasons. Specific sets of decision rules were written for irrigated and rainfed conditions. The establishment of rules was based on agronomic principles (e.g. for plant density) or on the application of a simulation model (e.g. for sowing date, variety). N fertilization and irrigation were applied using combined N and water dynamic models.

A novel methodology combining crop diagnosis, analytical trials and crop simulation was developed to evaluate the management systems. An irrigated and a rainfed rule-based management system were compared near Toulouse (S.W. France) from 1995 to 2002. The profitability of rainfed low-input management was confirmed for sorghum in spite of high yields under irrigation (up to 10 t ha⁻¹). The adaptation of sorghum management in rainfed conditions was mainly achieved through early maturing cultivars and by reducing N applications by 65%.     

An optimization model for zero-excess phosphorus management

Livestock production in the 21st century is moving in the direction of higher animal densities. Accompanying livestock expansion is the challenge of manure handling and utilization. A model for zero-excess phosphorus (ZEP) management has been developed for a dairy-crop operation that is based on multicriteria optimization. ZEP management practices are identified by simultaneously minimizing excess manure phosphorus, feed cost, and cropland requirement. System components include commercial fertilizer application, feed crop production, P storage in the soil profile, surface runoff, procurement of feed supplements, ration formulation, dairy herd structure and dynamics, manure handling, manure storage, and manure spreading. Manure is recycled as a fertilizer nutrient source in crop production. ZEP management practices include a cropping system, nutrient applications, and animal rations which are characterized by low feed cost and maximum use of land resources.     

Efficient use of water in the southern region of Portugal: agronomic aspects

The present paper analyses several aspects of agricultural production techniques and their relationship with an efficient water use paying special attention to the conditions prevailing in the Mediterranean environment. The agronomic aspects discussed are the following: crop rotation, seeding date and nitrogen fertilisation. With regard to the crop rotation in the effect of the preceding crop on the yield of the following wheat crop is analysed for different precipitation regimes as they frequently occur under Mediterranean conditions. What the concerned seeding date is and its effect on the water availability is studied for both the autumn and spring sown annual crops. Finally the importance of the quantity and distribution of the nitrogen fertilisation for reasonable crop yields in wet years is discussed.     

Cropcheck: Farmer benchmarking participatory model to improve productivity

In the 1970s in southern NSW, Australia, information was delivered to farmers through the transfer of technology (TOT) model. It was ‘top down’ with knowledge generated by researchers being passed onto farmers by extension officers. Farmers’ knowledge was not respected by research and extension workers. In contrast Cropcheck is a farmer participatory program which benchmarks farmer crops to identify practices for lifting yields. With TOT there was good adoption of single factor technologies such as wheat varieties but by the late 1970s to early 1980s wheat yields were stagnant or only slowly improving. There was the realisation that farmers had valuable knowledge and that multiple factors were needed to increase productivity. To address these needs in developing countries many farmer participatory models were developed. This paper, based on my experiences as an extension officer, records development in a developed country of a farmer participatory crop benchmarking model called Cropcheck. This program benchmarks farmer crops to identify the checks (best practices) related to high yields. It has been successful in lifting crop yields and profitability. This paper discusses the development of the model for irrigated wheat, i.e. the Finley Five Tonne Irrigated Wheat Club (referred to hereafter as “Wheat Club”) and adaption of the model for irrigated subterranean clover pasture, i.e. Subcheck. Since farmer participatory extension theory was undeveloped at that time, the development of the model was an intuitive learning process. The process was a planning, action and review cycle. Several years involving crop monitoring, farmer training, crop recording and reviewing results were needed to identify the objective checks consistently improving yields and gross margins. The results showed the more checks adopted the higher the yield and profitability. Farmers were trained in the learning steps of observing, monitoring, measuring, interpreting and recording their own crop practices. Farmer discussion groups were important for communication. Cropcheck has high farmer credibility because the checks are identified from farmer crops. Over a period of 6 years, yields of the “Wheat Club” increased by 50%. With Subcheck the problem of reddened subclover and inconsistent production disappeared. The Cropcheck model has been adapted for many crops in eastern Australia. Precision agriculture and electromagnetic mapping and geographic information systems (GIS) have followed on as new technology and monitoring tools for farmers but it is still important to ground truth these technologies with crop monitoring.     

InfoCrop: A dynamic simulation model for the assessment of crop yields,losses due to pests,and environmental impact of agro-ecosystems in tropical environments. II. Performance of the model

InfoCrop, a generic crop model, simulates the effects of weather, soils, agronomic management (planting, nitrogen, residues and irrigation) and major pests on crop growth, yield, soil carbon, nitrogen and water, and greenhouse gas emissions. This paper presents results of its evaluation in terms of its validation for rice and wheat crops in contrasting agro-environments of tropics, sensitivity to the key inputs, and also illustrates two typical applications of the model. Eleven diverse field experiments, having treatments of location, seasons, varieties, nitrogen management, organic matter, irrigation, and multiple pest incidences were used for validation. Grain yields in these experiments varied from 2.8 to 7.2 ton ha⁻¹ in rice and from 3.6 to 5.5 ton ha⁻¹ in wheat. The results indicated that the model was generally able to explain the differences in biomass, grain yield, emissions of carbon dioxide, methane and nitrous oxides, and long-term trends in soil organic carbon, in diverse agro-environments. The losses in dry matter and grain yield due to different pests and their populations were also explained satisfactorily. There were some discrepancies in the simulated emission of these gases during first few days after sowing/transplanting possibly because of the absence of tillage effects in the model. The sensitivity of the model to change in ambient temperature, crop duration and pest incidence was similar to the available field knowledge. The application of the model to quantify multiple pests damage through iso-loss curves is demonstrated. Another application illustrated is the use of InfoCrop for analyzing the trade-offs between increasing crop production, agronomic management strategies, and their global warming potential.     

Potassium carryover dynamics and optimal application policies in cotton production

Information about soil nutrient carryover dynamics can assist cotton producers with the optimal management of potassium (K) fertilizer. Optimal K management promotes cotton plant health, may decrease input costs, and increases cotton lint yields. A dynamic programming model was developed to determine optimal K application rates and economic returns under different soil information scenarios based on cotton yield response to K fertilizer and fertilizer carryover estimates from a multi-year field trial. A Monte Carlo analysis was conducted to simulate the impact of stochastic input and lint prices and cotton yield on K management over a five-period planning horizon. Results suggest that soil test data could provide important information about K carryover potential, which may lead to more efficient fertilizer use and higher profit margins for cotton producers.     

DRAINMOD-S: Water management model for irrigated arid lands,crop yield and applications

The primary objective of an agriculture water management system is to provide crop needs to sustain high yields. Another objective of equal or greater importance in some regions is to reduce agriculture impacts on surface and groundwater quality. Kandil et al. (1992) modified the water management model DRAINMOD to predict soil salinity as affected by irrigation water quality and drainage system design. The objectives of this study are to incorporate an algorithm to quantify the effects of stresses due to soil salinity on crop yields and to demonstrate the applications of the model. DRAINMOD-S, is capable of predicting the long-term effects of different irrigation and drainage practices on crop yields. The overall crop function in the model includes the effects of stresses caused by excessive soil water conditions (waterlogging), soil water-deficits, salinity, and planting delays. Three irrigation strategies and six drain spacings were considered for all crops. In the first irrigation strategy, the irrigation amounts were equal to evapotranspiration requirements by the crops, with the addition of a 10 cm depth of water for leaching applied during each growing season. In the second strategy, the leaching depth (10 cm) was applied before the growing season. In the third strategy, a leaching depth of 15 cm was applied before the growing season for each crop. Another strategy (4th) with more leaching was considered for bean which is the crop most sensitive to salinity. In the fourth strategy, 14 days intervals were used instead of 7 and leaching irrigations were applied: 15 cm before the growing season and 10 cm at the middle of the growing season for bean. The objective function for these simulations was crop yield. Soil water conditions and soil salinity were continuously simulated for a crop rotation of bean, cotton, maize, soybean, and wheat over a 19 years period. Yields of individual crops were predicted for each growing season. Results showed that the third irrigation strategy resulted in the highest yields for cotton, maize, soybean and wheat. Highest yields for bean were obtained by the fourth irrigation strategy. Results are also presented on the effects of drain depth and spacing on yields. DRAINMOD-S is written in Fortran and requires a PC with math-coprocessor. It was concluded that DRAINMOD-S is a useful tool for design and evaluation of irrigation and drainage systems in irrigated arid lands.     

配肥撒肥机研究及发展现状

化肥能够为农作物提供生长所需的营养成分,施用化肥对于农作物增产增收有重要意义。使用配肥撒肥机撒施肥料有助于减少化肥使用量,提高化肥利用率,对农民节省开支和增加收入以及环境保护等有积极的影响。分析了国内外配肥撒肥机的研究和发展现状,并针对国内配肥撒肥机存在的问题提出了发展对策。      

Enhancement of crop yields from subsurface drains with various envelopes

A field experiment was conducted for 10 years in the Nile Delta of Egypt to quantify the benefit of subsurface drainage on crop yield. During three crop rotations, subsurface drains at a spacing of 20 m and a depth of 1.5 m doubled the yield of cotton and rice and increased the yield of wheat and clover by 50%. No significant enhancement in crop yield was found from placing various envelope materials around the drains compared to no envelope. Drains of 75 mm diameter resulted in significantly lower yields (20% less) for cotton and rice than drains of 100 mm diameter but there were no yield differences for wheat and clover. Applying 10 Mg/ha of gypsum and deep plowing (25 cm deep) improved yields from 5 to 19% for all crops, cotton and clover having the largest yield improvement. Soil salinity to a depth of 1.5 m was reduced from an average 5.3–2.2 dS/m after 1 year of drainage without additional water being applied beyond the normal irrigation amounts and rainfall.     

Economic impacts on farm households due to water reallocation in China's Chaobai watershed

Our study area in the Chaobai watershed, upstream of Miyun Reservoir, has been undergoing agricultural water transfers to downstream municipal uses in Beijing. We examine the impacts of water reallocation on crop production and farmers’ income and discuss issues relating to current compensation mechanisms. We use data from a survey of 349 farm households and their farm plots in the upper Chaobai watershed within Hebei province. Water reallocation from upstream to downstream areas has reduced agricultural water supply and the area irrigated. Regression results show that in plots deprived of irrigation, maize yields decrease by 21% and crop revenues decline by 32%. On average, losing irrigation on one hectare of cultivated land reduces net crop income by 2422 yuan. We examine compensation arrangements and social equity for the major policies implemented in the region and we identify gaps between current compensation levels and farmers’ income and production losses. The current compensation received by farmers is generally lower than the losses incurred due to reduced irrigation. A more appropriate compensation mechanism is called for in future water transfers.     

Effect of mulching on soil and plant water status, and the growth and yield of wheat (Triticum aestivum L.) in a semi-arid environment

Mulching is one of the important agronomic practices in conserving the soil moisture and modifying the soil physical environment. Wheat, the second most important cereal crop in India, is sensitive to soil moisture stress. Field experiments were conducted during winter seasons of 2004-2005 and 2005-2006 in a sandy loam soil to evaluate the soil and plant water status in wheat under synthetic (transparent and black polyethylene) and organic (rice husk) mulches with limited irrigation and compared with adequate irrigation with no mulch (conventional practices by the farmers). Though all the mulch treatments improved the soil moisture status, rice husk was found to be superior in maintaining optimum soil moisture condition for crop use. The residual soil moisture was also minimum, indicating effective utilization of moisture by the crop under RH. The plant water status, as evaluated by relative water content and leaf water potential were favourable under RH. Specific leaf weight, root length density and dry biomass were also greater in this treatment. Optimum soil and canopy thermal environment of wheat with limited fluctuations were observed under RH, even during dry periods. This produced comparable yield with less water use, enhancing the water use efficiency. Therefore, it may be concluded that under limited irrigation condition, RH mulching will be beneficial for wheat as it is able to maintain better soil and plant water status, leading to higher grain yield and enhanced water use efficiency.