Economic contribution of French serradella (Ornithopus sativus Brot.) pasture to integrated weed management in Western Australian mixed‐farming systems: an application of compressed annealing*

Sowing phases of French serradella (Ornithopus sativus Brot.) pasture between extended cropping sequences in the Western Australian wheatbelt can sustain grain production through restoring soil fertility and reducing selective herbicide use. The objective of this article is to investigate the profitability of rotations involving this pasture under a variety of weed management scenarios to obtain greater insight into its value for mixed farming systems in this region. A stochastic search procedure, compressed annealing, is used to identify profitable sets of weed management strategies in a simulation model representing a large number of potential combinations of chemical and non‐chemical forms of weed control. In contrast to a continuous‐cropping sequence, the inclusion of a serradella phase in a rotation is profitable at high weed densities and with increasing levels of herbicide resistance. A single year of pasture in the rotation is optimal if resistance to Group A selective herbicides is present at the beginning of the planning horizon, but a three‐year phase is required if resistance to multiple herbicide groups is observed. Sowing a serradella pasture twice over a two‐year phase is also shown to be economically attractive given benefits of successive high weed kills.     

Evaluating combined land conservation benefits from perennial pasture: lucerne (Medicago sativa L.) for management of dryland salinity and herbicide resistance in Western Australia*

The inclusion of perennial pasture phases in cropping rotations has been widely promoted throughout Australia for reducing the incidence of dryland salinity. To a lesser extent, they have also been promoted to enhance the management of herbicide‐resistant weeds. No previous economic analysis of perennial pasture has considered both of these benefits. This study combines a dynamic linear programming model to estimate the magnitude of salinity‐related benefits and a complex simulation model to assess the economics of herbicide‐resistance management. We present a case study of the perennial pasture lucerne (Medicago sativa L.) in the Wheatbelt of Western Australia, where the weed annual ryegrass (Lolium rigidum Gaudin) is resistant to multiple herbicide groups. Sequences incorporating lucerne are the most profitable land use at the standard set of parameter values if (i) annual ryegrass is resistant to all selective herbicides, (ii) the water table is so shallow (approximately < 3.5 m deep) that frequent rotation with perennials is required to avert soil salinisation, (iii) sheep production is highly profitable, or (iv) there is a combination of less extreme cases. The value of perennial pasture is sufficient under these circumstances to overcome its high establishment cost and the displacement of multiple years of crop. Consideration of dryland salinity and herbicide resistance are about equally important in evaluating the economics of lucerne; neither should be neglected.     

State-conditional Fertilizer Yield Response on Western Kenyan Farms

Fertilizer interventions have attained prominence in rural poverty reduction programs in Africa. Using data from maize plots operated by small farmers in western Kenya, we find a von Liebig-type relationship between soil organic matter (SOM) and maize yield response to nitrogen application. Low SOM commonly limits the yield response to mineral fertilizer application. Although fertilizer is, on average, profitable in our sample, on roughly one-third of the plots degraded soils limit the marginal productivity of fertilizer such that it becomes unprofitable at prevailing prices. Moreover, because poorer farmers most commonly cultivate soils deficient in SOM, fertilizer interventions might be less pro-poor than is widely assumed and may instead reinforce  ex ante  income inequality.     

Push—pull technology: a conservation agriculture approach for integrated management of insect pests,weeds and soil health in Africa

Push—pull technology (www.push-pull.net) is based on a novel cropping system developed by the International Centre of Insect Physiology and Ecology, Rothamsted Research (UK) and national partners for integrated pest, weed and soil management in cereal—livestock farming systems. Stemborers are attracted to Napier grass (Pennisetum purpureum), a trap plant (pull), and are repelled from the main cereal crop using a repellent legume intercrop (push), desmodium (Desmodium spp.). Desmodium root exudates effectively control the parasitic striga weed by causing abortive germination. Desmodium also improves soil fertility through nitrogen fixation, natural mulching, improved biomass and control of erosion. Both companion plants provide high value animal fodder, facilitating milk production and diversifying farmers' income sources. The technology is appropriate to smallholder mixed cropping systems in Africa. It effectively addresses major production constraints, increases maize yields from below 1 to 3.5t/ha, and is economical as it is based on locally available plants, not expensive external inputs. Adopted by over 30,000 farmers to date in East Africa, key factors in its further up-scaling include effective technology dissemination, adaptability of companion plants for climate resilience, capacity building and multi-stakeholder collaboration, integration with livestock husbandry, improvement in input accessibility and creation of a supportive policy framework.     

定位培肥对东北黑土土壤固氮菌多样性的影响

基于10年的黑土培肥定位试验,本试验采用PCR-DGGE、克隆测序技术的方法,研究了培肥处理对大豆固氮菌多样性的影响。DGGE图谱分析表明对照土壤固氮菌多样性指数最高,其次为农肥低量处理、农化1:1处理、化肥低量处理和农肥高量处理,化肥高量处理土壤固氮菌多样性指数最低。在相似度60%水平上化肥处理聚成一群,对照、农肥处理和农化1:1处理量聚成一群。培肥处理降低了土壤固氮菌的多样性,影响了土壤中固氮菌的群落结构,其中培肥高量处理比低量处理降低土壤固氮菌多样性的效果更显著。     

Optimisation of a Large,Constrained Simulation Model using Compressed Annealing

Simulation models are valuable tools in the analysis of complex, highly constrained economic systems unsuitable for solution by mathematical programming. However, model size may hamper the efforts of practitioners to identify efficiently the most valuable management strategy. This paper investigates the efficacy of a new stochastic search procedure, compressed annealing, for the identification of profitable solutions in large, constrained systems. The algorithm is used to examine the value of incorporating a sown annual pasture, French serradella (Ornithopus sativus Brot. cv. Cadiz), between extended cropping sequences in the central wheatbelt of Western Australia. Compressed annealing is shown to be a reliable means of considering constraints in complex optimisation problems relative to the incorporation of fixed penalty factors in standard simulated annealing and genetic algorithms. French serradella is found to be an economic break pasture in the study region when weed populations are high or sheep production is lucrative.     

Profitability and opportunity of conservation agriculture in acid savannah grasslands of Laos

In north-eastern Laos, the savannah grasslands of the Plain of Jars cover vast areas of potentially cultivable land. However, soil acidity, low inherent fertility, and the absence of alternatives to tillage represent significant constraints to the development of sustainable smallholder agriculture. Our objective was to evaluate the potential for conservation agriculture (CA) to enhance soil productivity and farming system profitability. A three-year rotation of rice/maize/soybean was tested under three fertilization levels and four agricultural systems: one conventional tillage-based (CT) system and three CA systems based on no-tillage with cover crops. After four cropping seasons, our results show that, compared with CT, CA systems led to similar-to-higher grain production, similar-to-higher profits, higher opportunity of livestock system intensification, and higher labour productivity regardless of fertilization levels. While CA represents a relevant alternative to current practices, our results suggest that its contribution to the emergence of a sustainable smallholder agriculture is conditioned by broader institutional transformations, including the enrolment of local manufacturers and traders for deploying no-till implements and seed market channels for cover crops, long-term public support to maintain active research and technical mentoring to farmers, and possibly the integration of ecosystem services in agricultural policy.     

Factors influencing adoption of conservation tillage in Australian cropping regions*

The purpose of this research is to improve understanding of conservation tillage adoption decisions by identifying key biophysical and socio‐economic factors influencing no‐till adoption by grain growers across four Australian cropping regions. The study is based on interviews with 384 grain growers using a questionnaire aimed at eliciting perceptions relating to a range of possible long‐ and short‐term agronomic interactions associated with the relative economic advantage of shifting to a no‐tillage cropping system. Together with other farm and farmer‐specific variables, a dichotomous logistic regression analysis was used to identify opportunities for research and extension to facilitate more rapid adoption decisions. The broader systems approach to considering conservation tillage adoption identified important determinants of adoption not associated with soil conservation and erosion prevention benefits. Most growers recognised the erosion‐reducing benefits of no‐till but it was not an important factor in explaining whether a grower was an adopter or non‐adopter. Perceptions associated with shorter‐term crop production benefits under no‐till, such as the relative effectiveness of pre‐emergent herbicides and the ability to sow crops earlier on less rainfall were influential. Employment of a consultant and increased attendance of cropping extension activities were strongly associated with no‐till adoption, confirming the information and learning‐intensive nature of adopting no‐till cropping systems.     

An Economic Evaluation of Crop Rotations in Southwestern Saskatchewan

This study reports on an economic analysis of twelve crop rotations considered feasible for southwestern Saskatchewan. The results suggest that producers in this region should consider selecting a more intensive cropping system than has been the tradition. The three-year fallow-wheat-wheat rotation with recommended rates of nitrogen and phosphorus (N and P) fertilizers provided the highest expected net returns under most reasonable input cost and product price assumptions. Expected net returns for the traditional two-year wheat rotation and for the continuous wheat rotation averaged about 24 percent lower. The application of recommended rates of N fertilizer increased expected net farm income for the three-year and continuous wheat rotations by 6.6 and 10.5 percent, respectively. Use of P fertilizer in the three-year wheat rotation increased expected net farm income by an average of 20.6 percent. Average production costs increased as the proportion of summerfallow in the rotation decreased. Break-even stubble /fallow yield ratios that provided equivalent net returns from stubble and fallow cropping averaged 64 percent for the three-year wheat rotation and 76 percent for the continuous wheat rotation. Annual income variability was greatest for the continuous crop rotations and lowest for the two-year wheat rotation. Cette étude résume l'analyse économique de douze rotations de cultures jugées viables dans le Sud-Ouest de la Saskatchewan. Les résultats suggérent que les producteurs de cette région ont avanlage à considérer un systéme de production plus intensif que de par le passé. Les meilleurs revenus nets anticipés pour la plupart des suppositions raisonables des coúts de production et des prix des den rées furent accomptis avec la rotation de trois ans jachére-blé-bléfertilisée selon les recommendations en S et P. Les revenues nets anticipés avec la rotation traditionnelle de blé de deux ans (jachére-blé) et la rotation de blé continu furent en moyenne approximativement 24 pour-cent plus bas que la meilleure rotation. L'emploi d'engrais azotés aux taux recommendés augmenta le revenu net anticipé de 6,6 pour-cent pour la rotation de blé de trois ans et de 10.5 pour-cent pour la rotation de blé continu. L'amendement du sol en phosphate augmenta le revenu net anticipé de 20.6 pour-cent dans la rotation de blè de trois ans. Les coúrts deproduction augmentirènt à mesure que la proportion de Ierre en jachire duns la rotation diminuait. Les taux d'èquilibre des rendemenis chaume/jachire produisant des revenus nets equivalentr pour la culture sur le chaume el la jachire furenl en moyenne 64 pour-cent pour la rotation de blè de trois ans et 76 pour-cent pour la rotation de blè continu. La variabilite du revenu annuel fut la plus grande pour les rotations de culiures continues el la plus foible pour la rotation de blè de deux ans.     

A Methodology for Farm-Level Economic Analysis of Soil Erosion Effects Under Alternative Crop Rotational Systems in Ontario

Multiperiod linear programming techniques are used to evaluate comparative profitabilities and soil erosion rates for corn grown monoculturally and in rotation with a) soybeans, b) soybeans and oats, c) barley, and d) alfalfa on moderately sloping land with medium loam soils in southern Ontario. Attention is focussed on the case of a highly leveraged recent entrant to farming with heavy debt servicing needs and potential cash flow constraints. Monocultural corn was found to be more profitable than any of the rotational systems, with corn-soybeans rotations the next most profitable and corn-barley rotations the least profitable. Corn-soybeans caused the highest soil erosion, followed by continuous corn, with corn-alfalfa rotations causing the least. Les techniques de programmation linéaire multipériode sont utilisées pour évaluer et comparer les niveaux de profit et les taux d' érosion de sols agricoles moyennement argileux pour des systèmes de production de grandees cultyres localiées dans le sud de l' ontario et produisant, soit du mais en régime de monoculture, soit du mais en rotation avec: a) du soja, b) soja et avoine, c) orge. et d) de la luzerne plantée sur des terrains à pentes modérées. L' analyse developpée dans cet article met l' accent sur des agriculteurs récemment installés, disposant de beaucoup d' actifs, mais également, ayant des besoins énormes d' emprunts et, par conséquent, soumis à des contraintes potentielles sur leurs cash-flows. Les résultats obtenus montrent que le système de production, mais-monoculture, est le plus viable de tous les systèmes etudies. Parmi les systemes de production reposant sur une rotation culturale, il s' avère que celui combinant maïs et soja vienne en seconde position, tandis que un régime cultural fondé sur une rotation maïs et orge donne les pires resultats. Pour ce qui concerne des taux d' erosion des sols, la rotation maïs-soja cause les plus gros dommages. ensuite suivie par le système de production, maïs-monoculture. Finalement, les taux d' erosion les plus faibles ont été obtenus pour la rotation culturale, maïs-luzerne.     

The Economic Value of Soil Quality under Alternative Management in the Canadian Prairies

This paper describes a dynamic simulation model that integrates environmental and economic components of agricultural crop production systems to predict changes in soil quality and the concomitant impact on economic returns. The model is used to simulate crop yield, soil quality and economic performance of a conventional crop rotation and several alternative crop rotations in two contrasting environments in western Canada over a 50-year period. This information is used to quantify the impact of the crop rotations on soil organic carbon (SOC) and the economic value of on-site SOC changes. The estimated value of these impacts range from $0.20/t to $2.10/t of SOC/ha/yr.     

Improving recommendations resulting from on-farm research: agroforestry,risk, profitability and vulnerability in southern Malawi

Leguminous agroforestry (AF) species have been investigated and promoted in Malawi as a means to improve soil quality and maize (Zea mays) yields. Our objective was to determine whether AF systems' recommendations that solely consider impacts on average maize yields differ from those that include an analysis of production risk, profitability among different wealth groups and socioeconomic vulnerability. Employing participatory quantitative and qualitative on-farm research techniques, we investigated three AF-based maize/legume relay-cropping practices in southern Malawi. The perennial legumes included Sesbania sesban, Tephrosia vogelii and Cajanus cajan (pigeonpea). We found that AF species recommendations did diverge from those based solely on maximizing maize yields when incorporating risk, profitability and socioeconomic vulnerability as additional variables. For instance, the highest yielding system (the S. sesban/maize relay crop) was never recommended for the most vulnerable farmers based on the vulnerability analysis, and the cropping systems were often more profitable for the least vulnerable farmers than they were for the most vulnerable farmers. Cropping system recommendations based solely on obtaining the highest average maize yields would also have generally overlooked the economic and nutritional importance of pigeonpea, and the difficulty for the most vulnerable farmers to profit from fertilizers, potentially placing these farmers at greater risk.     

Optimal management of annual ryegrass (Lolium rigidum Gaud.) in phase rotations in the Western Australian Wheatbelt*

Lucerne (Medicago sativa L.) helps to prevent soil salinisation in the Western Australian Wheatbelt by reducing recharge to saline water tables. There is broad consensus, though, that it is not sufficiently profitable to motivate producers to plant it at the intensity at which considerable off‐site benefits would be conferred. This paper employs a multiple‐phase optimal control model to explore the value of this perennial pasture for the management of herbicide‐resistant annual ryegrass (Lolium rigidum Gaud.) in a crop–pasture rotation, given the difficulty of observing this value in practice. The availability of selective herbicides for efficient weed control is found to determine whether or not it is profitable to adopt lucerne pasture under optimal management. Herbicide resistance requires producers to employ costly, non‐selective treatments for in‐crop weed control. Thus, it motivates the adoption of perennial pasture in which cost‐effective forms of control can be implemented. Moreover, this result is robust to feasible changes in the current economic environment.     

From weed to wealth? Prospects for medic pastures in the Mediterranean farming system of north-west Syria

Medic (Medicago spp.) pastures are widely grown in rotation with dryland cereal crops in Mediterranean climate zones of Australia. Attempts since the 1960's to introduce this system to Mediterranean west Asia and north Africa (the native region of medic) have not lead to significant adoption; farmers in the region recognize medic, but as a weed and natural pasture plant. This first detailed economic evaluation of the rotational medic system was conducted using a whole-farm linear programming model based on the agricultural system of north-west Syria. The model represents in detail impacts of rotation on yields, labor requirements of alternative farm activities, availability of family and hired labor, subsistence income requirements, livestock feed sources and uses at different times and a choice of sheep stocking rates. Biological data for the analysis are based on a large six-year cropping and grazing experiment near Aleppo on terra-rossa soil with rainfall mainly in winter and averaging about 330 mm annually. The trial compared a dryland medic-wheat system and traditional two-year rotations of wheat with: fallow, watermelon, lentil and vetch. Results indicate that, given current prices and yields from the trial, medic is less profitable than traditional rotations. The model was used to investigate situations in which medic would be economically preferred. Selection of a medic rotation by the model was found to be particularly sensitive to the area of the farm and the price of labor. On small farms, labor availability per hectare is high, favouring the production of labor intensive crops such as lentil and watermelon. On larger farms, labor costs of these enterprises are substantial, increasing the relative profitability of medic, especially if labor prices increase. Interestingly, the relative desirability of medic is more sensitive to its impact on subsequent wheat crops than to the level of pasture production. We also found that modest increases in the prices of sheep products (especially milk) have a major impact on the economic performance of medic. These insights will allow improved focusing and targeting of future research and extension activities.     

Red clover (Trifolium pratense) in conservation agriculture: a compelling case for increased adoption

The rapidly growing population will soon require a near doubling of food production. This increase must be achieved in a manner that maintains environmental integrity, preserves public health and resolves food access and distribution equalities. The use of forage legumes in arable rotations can make significant and multidimensional contributions to this sustainable intensification and this paper reviews the potential contribution of red clover (Trifolium pratense L.), with particular reference to sustainable cereal production in conservation agriculture systems. The use of red clover as a tool in soil fertility-building and the multiple benefits to the cropping system in which it is used is described. The benefits discussed include atmospheric nitrogen fixation, soil conservation, structural soil improvements and a suite of agroecosystem services including increased soil microbial activity, the phytoremediation of polluted soils and the provision of food for pollinators. Reported allelopathic weed suppression by red clover cover crops and the role of modern plant breeding in creating new varieties that further enhance system sustainability is also discussed. Finally, as economic considerations will always impact on adoption rates, the profitability of red clover rotations in terms of silage value and yield benefits is taken into account.     

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.     

Economywide effects of climate‐smart agriculture in Ethiopia

Climate‐smart agriculture (CSA) is an approach for transforming and reorienting agricultural systems to support food security under climate change. Few studies, however, quantify at the national scale CSA's economic effects or compare CSA to input‐intensive technologies, like fertilizer or irrigation. Such quantification may help with priority setting among competing agricultural investment options. Our study uses an integrated biophysical and economic modeling approach to quantify and contrast the economywide effects of CSA (integrated soil fertility management in our study) and input‐intensive technologies in Ethiopia's cereal systems. We simulate impacts for 20‐year sequences of variable weather, with and without climate change. Results indicate that adopting CSA on 25% of Ethiopia's maize and wheat land increases annual gross domestic product (GDP) by an average 0.18% (US$49.8 million) and reduces the national poverty rate by 0.15 percentage points (112,100 people). CSA is more effective than doubling fertilizer use on the same area, which increases GDP by US$33.0 million and assists 75,300 people out of poverty. CSA and fertilizer have some substitutability, but CSA and irrigation appear complementary. Although not a panacea for food security concerns, greater adoption of CSA in Ethiopia could deliver economic gains but would need substantial tailoring to farmer‐specific contexts.     

Soil quality and fertilizer use rates among smallholder farmers in western Kenya

Studies of fertilizer use in sub-Saharan Africa have been dominated by analyses of economic and market factors having to do with infrastructure, institutions, and incentives that prevent or foster increased fertilizer demand, largely ignoring how soil fertility status conditions farmer demand for fertilizer. We apply a switching regression model to data from 260 farm households in western Kenya in order to allow for the possibility of discontinuities in fertilizer demand based on a soil carbon content (SCC) threshold. We find that the usual factors reflecting liquidity and quasi-fixed inputs are important on high-SCC plots but not on those with poorer soils. External inputs become less effective on soils with low SCC, hence the discernible shift in behaviors across soil quality regimes. For many farmers, improved fertilizer market conditions alone may be insufficient to stimulate increased fertilizer use without complementary improvements in the biophysical conditions that affect conditional factor demand.     

长期不同施肥处理对棕壤不同组分有机碳的影响

以沈阳农业大学棕壤长期定位试验站土样为材料,对长期施肥条件下不同施肥处理土壤有机碳、活性有机碳和颗粒有机碳进行了研究.结果表明:有机肥配施化肥有利于提高棕壤有机碳含量,长期不同施肥处理对土壤水溶性有机碳和微生物量碳的影响差异显著,高量有机肥与化肥配施处理含量最高,长期施用化肥降低了土壤颗粒有机碳含量,有机肥的施用可以显...     

Net Greenhouse Gas Emissions and the Economics of Annual Crop Management Systems

The aim of this study was to evaluate the relative economic profitability and net greenhouse gas (GHG) abatement potential of alternative tillage and cropping systems. A simulation model was parameterized using biophysical and economic data representing different crop rotations under conventional, minimum, and zero tillage cropping systems, in the Black soil zone of Saskatchewan. This model was used to estimate the relative potential of each of the management practices to sequester carbon and to emit GHG including, nitrous oxide and carbon dioxide. The model also provided estimates of the relative profitability of each of the management practices over time horizons of 30 years. These simulation results were used to develop trade-off functions reflecting net income and net GHG abatement for each cropping system. An income risk measure was incorporated to facilitate an analysis of the relative economic attractiveness of the simulated cropping systems. Furthermore, sensitivity analysis was performed on nitrous oxide emission coefficients (an area of significant uncertainty in the literature) and on weather patterns to reflect uncertain future climate change impacts. Results indicated that net GHG emissions were relatively lower for reduced tillage management, while conventional tillage may be relatively more attractive from an economic perspective. However, results also indicated that such economic factors as risk and economies of size may have a significant influence on this latter result.