Comparison of mechanized conservation agriculture and conventional tillage in Zambia: A short-term agronomic and economic analysis

Abstract

The rise of medium-scale farmers across sub-Saharan Africa (SSA) is offering Conservation agriculture (CA) a new perspective. Such farmers not only cultivate increasingly large land areas but also provide machinery services, share knowledge, and can act as role models to smallholders. Although mechanization may incentivize CA adoption in SSA, little research has focused on the performance of mechanized CA using four-wheel tractors (4WTs). This study explores the short-term agronomic and economic differences between mechanized conventional tillage and mechanized CA. An on-farm experiment was set up in a randomized complete block design in Zambia to compare 1) disc harrowing (DH) plus residue burning, 2) ripping tillage (RT), and 3) direct seeding (DS) plus soil cover. The experiment focused on maize and soyabean and covered two years, of which the first was more “dry” and the second more “wet”. All treatments were replicated four times and crops were rotated in the subsequent season. All operations were performed using a 60 hp 4WT. For both maize and soyabeans, DS and RT treatments resulted in higher grain yields during the dry season than DH. However, in the wet season, DH and RT resulted in significantly higher yields than DS for maize, but not for soyabeans. RT and DS plots showed higher plant densities in maize and soyabeans at germination and maturity than DH plots. RT plots produced significantly higher maize vegetative biomass (5928 kg ha−1) in the dry season while in the wet season DS recorded significantly higher biomass yields (7886 kg ha−1). The cumulative time for all agronomic operations except harvesting for both maize and soyabean was significantly lower in DS while DH and RT treatments recorded no significant differences. Fuel-saving was significantly higher in DS and RT than in DH plots for the two crops. Maize gross margin was highest in DS plots (US$790 ha-1) in the dry season compared to US$746 ha-1 for DH and US$768ha-1 for RT. In the wet season, DH plots had the highest gross margins for maize (US$685 ha-1) as compared to US$576 ha-1 for DS and US$581 ha-1 for RT. Regarding soyabeans, DS treatments had the highest gross margins in both seasons, US$537 ha-1 and US$392 ha-1, respectively. The results of this short-term study demonstrate the potential of mechanized CA among small and medium-scale farmers in SSA.