Open access publications in the SLU publication database

Abstract

Integrated soil fertility management combining additions of organic and mineral fertilizers and reduced ploughing frequencies is a prospective option for sustainable cropping systems. In the cotton cultivation area of Burkina Faso the agricultural land is gradually degrading due (at least in part) to increases in mechanization and the use of mineral fertilizers, herbicides and pesticides. The objective of the work underlying this thesis was to test soil management techniques to improve soil fertility, and the productivity of cotton (Gossypium hirsutum) and maize (Zea mays). For this purpose, a research program was initiated in 2003 at Bondoukuy in the western cotton growing zone of the country. On-farm experiments combining two tillage regimes - annual ox-ploughing (AP) and ox-ploughing/hand hoe scarifying in alternate years, referred to as reduced tillage (RT) - with or without compost addition in a cotton-maize rotation were carried out on two common soil types (a Ferric Lixisol and a Ferric Luvisol). We investigated the effects of the treatments on: (i) soil aggregate stability, (ii) soil infiltrability, and (iii) crops nutrient uptakes and yields. Reduced tillage resulted in greater macroaggregate stability than annual ploughing in both soil types. The compost addition treatments (in combination with annual ploughing or reduced tillage) increased soil saturated hydraulic conductivity (Ks) compared to the annual ploughing without compost addition (control). The soil nutrient status was related to organic and mineral fertilizer inputs, and soil carbon and nitrogen contents were highest (ca 0.6% C and 0.05% N) in plots where compost was applied, after the third year of the experiment. Reducing tillage had no clear effect on cotton and maize nutrient uptake, but compost applications increased N and P uptake by cotton in both soil types. On both soil types, the cotton fibre yields under the reduced tillage regime with compost additions were higher than those obtained under the control, although the differences were not always statistically significant. The trend of maize production was: higher production under the annual ploughing with compost addition than the control on the Lixisol, while it was the reduced tillage with compost addition, on the Luvisol. The results supported earlier conclusion that the effects of soil management techniques on crop production depend on the seasonal rainfall pattern. In spite of the short term of the experiment, reduced tillage with compost addition seems to be a suitable option for the smallholder farmers. As recommendation; soil fertility management regimes in the cotton maize rotation system should mix compost application or other organic matter source with mineral fertilizer, and should consider ploughing frequency.