Where is the limit? lessons learned from long-term conservation agriculture research in Zimuto Communal Area, Zimbabwe

Abstract

Smallholder farming in Zimbabwe is increasingly affected by dwindling maize (Zea mays L.) yields due to declining soil fertility and the negative effects of climate variability and change. A long-term on-farm study was established between 2004 and 2013 at the Zimuto Communal Area near Masvingo, Southern Zimbabwe to test the feasibility and viability of conservation agriculture (CA) systems under the circumstances of low fertility and erratic rainfall. CA seeding systems based on animal traction excelled and significantly increased maize productivity by up to 235% (1761 kg ha -1 ) and legume productivity by 173% (265 kg ha -1 ) as compared to the conventional control treatment. Soil quality indicators such as infiltration and soil carbon improved 64-96% and 29-97 %, respectively, over time. However, a direct link between increased infiltration and grain yield could not be established. Increased plant population, because of greater precision and moisture conservation during direct seeding as well as an improved response to fertilizer application due to gradually increasing soil carbon could be the reasons why yields on CA systems outyielded the conventional control. CA systems were more economically viable than planting crops under the normal conventional practice with mouldboard ploughs and removal of crop residues. Farmers generally rated important crop characteristics of maize planted under CA as high but weed control was rated as low, due to the lack of an appropriate herbicide under the prevailing environment. The results of this study show that CA is a potential option even in areas of climate risk and low soil fertility. However, the adoption of CA was low amongst members of the rural farming community due to the perceived risk of crop failure, lack of appropriate and accessible inputs and markets for farm produce, and lack of appropriate information and knowledge about alternative agricultural methods. This highlights the need for better resource and input availability as well as more vibrant and efficient extension services. Successful CA promotion requires that the systems are adapted to farmers' circumstances. However, CA cannot expand where farmers depend on remittances, are donor dependent, and where crop production in general is doubtful. Land uses such as extensive livestock production or game ranching may be better and more profitable alternatives for farmers in these situations.

Where to Target Conservation Agriculture for African Smallholders? How to Overcome Challenges Associated with its Implementation? Experience from Eastern and Southern Africa

“…Comparison of rainwater use efficiency of maize during five consecutive seasons for conventional practice and conservation agriculture in Zimuto, Zimbabwe (source: calculated from [24]). …”

Evidence and Lessons Learned from Long-Term On-Farm Research on Conservation Agriculture Systems in Communities in Malawi and Zimbabwe

“…The farmers were used as blocks in the analysis. The size of each farmer replicate was 3000 m 2 subdivided into treatments of each 1000 m 2 (for more details on the design consult [30] and [40]. At Zidyana the treatments were as follows:…”

“…Notes: VC: variable costs, TVC: total variable costs, CP = conventionally ridge tillage; CA + maize = conservation agriculture treatment seeded with a dibble stick and sole maize; CA + maize / legume = conservation agriculture treatment seeded with a dibble stick and maize-cowpea intercropping; The labour data is an aggregate from 6 farmers in the area. [30]. The labour data is an aggregate from 7 farmers in Zimuto.…”

“…In large parts of the communal land of Zimbabwe, soils are derived from granitic sands with high sand content (>90%) and low soil organic matter levels (<0.5%). Average yields are below 1 t· ha −1 [30,31]. In Malawi, soils are more fertile and farmers have access to a government implemented fertilizer subsidy program leading to relatively higher average maize grain yields (±2 t· ha −1 ) as compared with Zimbabwe [9].…”

“…However, the dependency of farmers to the fertilizer subsidy program also raised concerns [32,33] as it has large budgetary implications for the Malawi Government. Farmers in conventional agriculture systems of southern Zimbabwe rarely break even [30] whereas Malawian farmers, especially if beneficiaries of the subsidy program have greater gross margins per hectare [9]. Due to the complexity of smallholder farming systems in sub-Saharan Africa, which are related to multiple crops grown on the farms and integration of livestock to varying degrees [34], the aforementioned constraints, the mindset and beliefs of farmers, lack of consistent messages and approaches in the extension of CA [5], the adoption of CA practices on larger farm areas has been lower than in other parts of the world.…”