Evaluation of Resource Management Options for Smallholder Farms Using an Integrated Modelling Approach

Farm-level analysis of trade-offs between soil fertility management alternatives is required to improve understanding of complex biophysical and socio-economic factors influencing decision making in smallholder farming systems and to identify opportunities for improving resource use efficiency. A farm characterization tool (IMPACT) linked to a generic optimization model (Household) was used to evaluate resource use on farms in contrasting wealth categories. The Household model optimized the net cash income for the farms (accounting for all on-farm and off-farm income, costs of production and expenditure for the households). Alternatives for management of nutrient resource were simulated using other models; APSIM for the crop production and RUMINANT for the livestock component. The output from the simulation models was fed into the Household model and evaluated within the biophysical and socioeconomic boundaries of the farms. Analysis of the performance of a poor farmer by IMPACT indicated a yearly net cash balance of US$-7 per annum (after all needs had been taken care of), mainly due to negative returns from the cropping system. The farmer relied on donated food and fertilizers. The cash balance was negative, even though she also worked for other farmers (i.e. sold labour, about 10 days a month during six months of the crop growing season) to generate income. The net income of the poor farm would be increased to US$81 per annum and the N balance from 7 kg ha-1 yr-1 to 10 kg ha-1 yr-1 by expanding the area allocated to groundnut from the current 5% to 31%. This would, however, generate a huge demand in labour in the current year (extra 46-man days) and reduce the P balance from 0 to -1 kg ha-1 yr-1. Maize could be managed more efficiently on the poor farm by cultivating a smaller, well-managed area. A wealthy farm household with a maize dominated cropping system had a net cash balance of US$210 per annum, mainly from sale of crop products. Under current resource management, the net cash balance could be increased to US$290 per annum by optimization of household energy and protein consumption. The net cash balance for the wealthy farm would be further increased to US$448 per annum, and nutrient balances to 271 kg N ha-1 and 30 kg P ha-1 by expanding the management strategy where maize was grown with a combination of cattle manure and ammonium nitrate fertilizer. To do this, the farmer would need to source more manure (or improve capture and the efficiency with which nutrients are cycled through manure) and invest in 110 man-days extra labour. Expansion of the area grown to groundnut without fertilizer inputs to a third of the farm would reduce net cash balance by US$11 compared with the current crop allocation due to poor groundnut yield. This would also increase labour demand by 155 mandays. Groundnut intensification on the wealthy farm would be more economic and labour effective if a small area was grown with basal fertilizer (7%N, 6%P, 8%K). Despite reducing nutrient balances for the arable plots, feeding groundnut residues to lactating cows increased net cash balance by 12-18% for the current year through increased milk production. The integrated modelling approach was useful for linking biophysical and socio-economic factors influencing decision making on smallholder farms and evaluating trade-offs for resource use in terms of nutrient balances, labour use, food sufficiency and cash balance.Farm Management, Resource /Energy Economics and Policy,

Testing the APSIM model with data from a phosphorus and nitrogen replenishment experiment on an oxisol in

Abstract An experiment was conducted on an Oxisol near Maseno in western Kenya, to compare the growth of maize crops to inputs of two phosphorus sources. Commercial triple superphosphate (TSP) and Minjingu phosphate rock were applied either at a once-only rate of 250 kg P ha -1 or as five annual inputs of 50 kg P ha -1 . The experiment was carried out over 10 cropping seasons between 1996 and 2000. An additional factor studied was the source of N, either as urea or tithonia biomass-N to supply 60 kg N ha -1 . Both N and P sources were applied only to the crops grown in the long rain season. The APSIM model has been tested against this data set. The effects of P treatments were large in the long rain season, but in the short rain season the inadequate supply of N greatly reduced growth and P effects. The yields of the maize crops were predicted well (r 2 = 0.88) with respect to both the P treatments (as TSP) and the N inputs (as urea). The predicted water, N and P stresses were informative in understanding the contrasting pattern of response observed in the two seasons. The simulation of this long-term experiment shows that the APSIM SoilP module is robust, in as much as it extends the testing of the model to a very different environment where there were both N and P stresses affecting plant growth, and on a very different soil type to where the concepts in the APSIM phosphorus routines were originally developed and tested. Crop production on many soils in western Kenya is limited by both nitrogen (N) and phosphorus (P). The concept of recapitalisation of soil P has focused attention on the use of rock phosphate materials rather than commercial forms of processed fertilisers, and the feasibility of raising soil P through large, one-time application rather than a gradual increase with smaller, but regular inputs . Such strategies have been evaluated in long-term experiments in western Kenya. Probert In this paper, we describe the testing of the APSIM P routines using an experiment that provides suitable data for testing some aspects of the model. The annual rainfall and soil type, especially with regards to its phosphorus sorption properties, ar

Drivers of land use change and household determinants of sustainability in smallholder farming systems of Eastern Uganda

Smallholder farming systems in sub-Saharan Africa have undergone changes in land use, productivity and sustainability. Understanding of the drivers that have led to changes in land use in these systems and factors that influence the systems’ sustainability is useful to guide appropriate targeting of intervention strategies for improvement. We studied low input Teso farming systems in eastern Uganda from 1960 to 2001 in a place-based analysis combined with a comparative analysis of similar low input systems in southern Mali. This study showed that policy-institutional factors next to population growth have driven land use changes in the Teso systems, and that nutrient balances of farm households are useful indicators to identify their sustainability. During the period of analysis, the fraction of land under cultivation increased from 46 to 78%, and communal grazing lands nearly completely disappeared. Cropping diversified over time; cassava overtook cotton and millet in importance, and rice emerged as an alternative cash crop. Impacts of political instability, such as the collapse of cotton marketing and land management institutions, of communal labour arrangements and aggravation of cattle rustling were linked to the changes. Crop productivity in the farming systems is poor and nutrient balances differed between farm types. Balances of N, P and K were all positive for larger farms (LF) that had more cattle and derived a larger proportion of their income from off-farm activities, whereas on the medium farms (MF), small farms with cattle (SF1) and without cattle (SF2) balances were mostly negative. Sustainability of the farming system is driven by livestock, crop production, labour and access to off-farm income. Building private public partnerships around market-oriented crops can be an entry point for encouraging investment in use of external nutrient inputs to boost productivity in such African farming systems. However, intervention strategies should recognise the diversity and heterogeneity between farms to ensure efficient use of these external inputs

Effect of soil fertility management strategies and resource-endowment on spatial soil fertility gradients, plant nutrient uptake and maize growth at two smallholder areas, north-western Zimbabwe

We investigate the effects of smallholder farmer resource-endowment and soil nutrient management strategies on plant nutrient uptake and growth across soil fertility gradients under semi-arid conditions. Soil fertility gradients as influenced by farmers’ resource availability may affect the response of crops to fertilizer addition and therefore productivity. The study was conducted in Njelele and Nemangwe smallholder areas (450-800 mm per annum, unimodal) in north-western Zimbabwe. Soil and maize cobleaf samples were collected from fields of farmers (varying resource endowment) located near to (homefields) and far away (outfields) from the farmers’ homesteads during the 2005-6 season. The samples were analysed for selected soil fertility indicators and soil samples were further used to test maize growth response to various nutrient applications under greenhouse conditions. Soil fertility (organic C, total N and available P) significantly (P<0.05) decreased from resourceendowed to resource-constrained farmers, and from outfields to homefields, but the latter differences were only significant for available P. Besides resource-endowment and field type, response to nutrient applications also depended on soil texture. In sandy soil, both N and P were limiting to MAIZE growth in outfields while N was most limiting in the homefield. It was concluded that resource-endowment and nutrient resource management strategies employed by farmers result in soil fertility gradients which affect response of crops to fertilisation and therefore need to be factored in the development of fertiliser recommendations

YAP/TAZ regulates the expression of proteoglycan 4 and tenascin C in superficial-zone chondrocytes

The roles of cell division control protein 42 homologue (CDC42) and actin polymerisation in regulating the phenotype of superficial-zone chondrocytes (SZCs) have been demonstrated in vitro; however, the signalling pathway(s) downstream have yet to be fully elucidated. The study hypothesis was that Yes-associated protein (YAP) and transcriptional co-activator with PDZ-binding motif (TAZ) act downstream to regulate proteoglycan 4 (PRG4) and tenascin C (TNC). Bovine SZCs grown in monolayer were treated with ML141 (CDC42 inhibitor) or the actin depolymerising agents, latrunculin B and cytochalasin D, to determine the effect on YAP/TAZ. Verteporfin (YAP/TAZ inhibitor) and YAP/TAZ siRNA-mediated knockdown were used to determine their role in regulating PRG4 and TNC. ML141 treatment reduced total YAP/TAZ protein, nuclear TAZ levels and the YAP/TAZ target gene, connective tissue growth factor (CTGF) mRNA levels. Latrunculin B decreased nuclear TAZ, while cytochalasin D treatment trended towards increased nuclear TAZ (p = 0.06), correlating with decreased and increased CTGF mRNA levels, respectively. Verteporfin treatment decreased PRG4 and TNC expression, with no effect on actin polymerisation. siRNA-mediated knockdown of YAP/TAZ revealed that PRG4 was regulated by YAP/TAZ while TNC was regulated by TAZ only. As cytochalasin D can activate myocardin-related transcription factor-A (MRTF-A), siRNA-mediated knockdown was performed to determine the role of MRTF-A in regulating YAP/TAZ. Although nuclear TAZ decreased, no significant changes in total protein levels were observed. Findings suggested that CDC42 and actin polymerisation regulated SZCs through multiple actin-regulated pathways. Understanding the regulation of these chondroprotective molecules may have important implications for prevention/treatment of osteoarthritis

Indicators of soil quality: a South-South development of a methdological guide for linking local and technical knowledge

The increasing attention paid to local soil knowledge results from a greater recognition that farmer knowledge can offer many insights into the sustainable management of tropical soils and that the integration of local and technical knowledge systems helps extension workers and scientists work more closely with farmers. A participatory approach and a methodological guide were developed to identify and classify local indicators of soil quality and relate them to technical soil parameters, and thus develop a common language between farmers, extension workers and scientists. This methodological guide was initially developed and used in Latin America and the Caribbean-LAC (Honduras, Nicaragua, Colombia, Peru, Venezuela, Dominican Republic), and was later improved during adaptation and use in eastern African (Uganda, Tanzania, Kenya, Ethiopia) through a South–South exchange of expertise and experiences. The aim of the methodological guide is to constitute an initial step in the empowerment of local communities to develop a local soil quality monitoring and decision-making system for better management of soil resources. This approach uses consensus building to develop practical solutions to soil management constraints identified, as well as to monitor the impact of management strategies implemented to address these constraints. The particular focus on local and technical indicators of agroecosystem change is useful for providing farmers with early warnings about unobservable changes in soil properties before they lead to more serious and visible forms of soil degradation. The methodological approach presented here constitutes one tool to incorporate local demands and perceptions of soil management constraints as an essential input to relevant research for development activities. The participatory process followed was effective in facilitating farmer consensus; for example, about which soil related constraints were most important and what potential soil management options could be used. Development of local capacities for consensus building constitute a critical step prior to collective action by farming communities resulting in the adoption of integrated soil fertility management strategies at the farm and landscape scale

Modelling nitrogen mineralization from manures: representing quality aspects by varying C:N ratio of sub-pools

The mineralization/immobilization of nitrogen when organic sources are added to soil is represented in many simulation models as the outcome of decomposition of the added material and synthesis of soil organic matter. These models are able to capture the pattern of N release that is attributable to the N concentration of plant materials, or more generally the C:N ratio of the organic input. However, the models are unable to simulate the more complex pattern of N release that has been observed for some animal manures, notably materials that exhibit initial immobilization of N even when the C:N of the material suggests it should mineralize N. The APSIM SoilN module was modified so that the three pools that constitute added organic matter could be specified in terms of both the fraction of carbon in each pool and also their C:N ratios (previously it has been assumed that all pools have the same C:N ratio). It is shown that the revised model is better able to simulate the general patterns on N mineralized that has been reported for various organic sources. By associating the model parameters with measured properties (the pool that decomposes most rapidly equates with water-soluble C and N; the pool that decomposes slowest equates with lignin-C) the model performed better than the unmodified model in simulating the N mineralization from a range of feeds and faecal materials measured in an incubation experimen