Residue management strategies for the rainfed N-deprived maize-legume cropping systems of central Mozambique

Abstract

Identifying best-fit residue management strategies for Central Mozambique rain fed Ndeprived maize-legume cropping (LEINA) systems managed under conservation agriculture is critical to improve resource use efficiency and yields. Therefore, understanding under what circumstances positive and negative responses from carbon rich residue mulches are likely to occur and what drives farmers' decision on the adoption of technologies is critical to design relevant and feasible recommendations that fit farmers complex farming circumstances. Here I used household survey data, field experimentation and cropping systems modelling to: 1) characterize farm diversity and understand how it affects smallholder farmers resource use attitudes, management decisions and the likelihood to engage in sustainable intensification (SI) practices; 2) identify best-fit residue management strategies that are more likely to improve resource productivity and yields; and 3) develop simple rules of thumb to match residue management solutions to N-deprived smallholder farming systems.Household characterization data showed that, rather than farm size and labour availability, farmers resource use attitudes and household capacity to meet its annual food security and income generation targets where key farm differentiation factors, therefore critical to map farm typology feasible intensification options. Using a heuristic decision tree to group smallholder farmer into a new set of mutually exclusive farm typologies that highlight existing intragroup diversity among Mozambican small-scale farmers, three key typologies where identified. The resource endowed and innovative farmers (Type B); resource endowed but change resistant farmers (Type -A2); and resource constrained (Type -A1) farmers, who can also be maize self-sufficiency (Type-A1a) and the food insecure (Type-A1b). For the already maize self-sufficient Type-B and Type-A2 farms, the challenge is to improve agronomy to generate enough surplus and income from maize. Mechanization and labour qualification are critical for these groups. For resource constrained Type-A1 farmers, the primary challenge towards intensification is to generate enough income to improve the household maize self-sufficiency and income in the system. Considering its high market value and further contribution to soil N-availability, legume production is a feasible investment alternative. Nevertheless, two key intensification traps were identified: the household maize self-sufficiency and soil fertility perception, and land availability perception trap (extensification). The traps are perception based mind-sets that reflect farmers understanding of their circumstances and the strategies they use to materialize their annual food security and income generation targets. Page | iiField trials and model-assisted analyses (64 years) of carbon rich residues effects on a cereal (maize) and a legume (cowpea) crop, at different levels of N supply, and three soils of contrasting water holding capacity (WHC) showed that for Central...

Optimizing the Nitrogen Use Efficiency in Vegetable Crops

“…A study conducted in a rainfed arid region of central Mozambique found a differential effect in the response to organic mulch applications, depending on the soil moisture holding capacity of the soils. Crop residue applications increased the WUE and NUE in soils with a low water holding capacity, while these variables were reduced when residues with a high C/N ratio were applied on soils with a high water holding capacity, apparently fixing the available N for their microbial decomposition [242].…”

“…Crop responses to N x water interactions Broccoli (tunnels), Cabbage; Greenhouse cucumbers; African eggplant (Solanum aethiopicum L,); Onions; tomato [239,[245][246][247]249,250] Cultivar selection Selection of early maturing cultivars during drought periods [251] Fertigation Improved NUE [24,171,238] Irrigation system selection Effect on moisture uniformity, WUE x N x yields [231,249] Irrigation rates and timing Irrigation x N interaction [239] Organic Mulches Reduced evapotranspiration and erosion; moderates soil temperature and moisture; N cycling [43,242] Plastic mulches Reduced evapotranspiration and erosion; moderates soil temperature and moisture [43,69] Rotations Water and NUE [243,244] Tillage Moisture retention under no-till farming and NUE [235]…”