L’agriculture de conservation peut-elle améliorer la fertilité des sols et la productivité des systèmes bananiers en Région des Grands Lacs ?
(2018)
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- Abstract
- Banana is one of the main crops in Burundi, Rwanda and South Kivu (DRC), as in the whole of the African Great Lakes Region. Its cultural potential amounts to 60-70 T ha-1 yr-1. Real crop yields deviate from this potential, but in an extremely variable way. The cropping conditions vary as much, in terms of climates, soils and technical routes. By diagnostic survey, we have quantified the variability of banana crop yields and investigated the influence of climate, soil and management practices in fourteen sites in Burundi, Rwanda and South Kivu. Up to seven times higher than those reported in national statistics, yields range from 13 to 37 T ha-1 yr-1. Their variability is due to very marked differences in water and nutrients availability, as well as in management practices. Water constraint and mineral deficiencies, including potassium, phosphorus, and magnesium, are major limiting factors to crop yields. The diagnostic survey also reveals that some practices can be used to correct the environment, particularly non-tillage with mulching and intercropping. The contribution of soil to crop performance is assessed at five sites. Their altitude varies from 880 to nearly 1700 m, the average annual precipitation from 900 to 1600 mm, while the Total Mineral Reserve (TRB) ranges from 10 to 160 cmolc kg-1. The latter is decisive in determining the real yield RY in the absence of fertilizer inputs. Indeed, in these conditions, RY (T ha-1 yr-1) is a relevant indicator of the soil weathering degree (/TRB, cmolc kg-1): RY = 0 (Acrisol/TRB = 10), 1.5 (Ferralsol/44-53), 4.3 (Nitisol/40), 16.6 (Cambisol protoandique/112-115), 25.0 (Fluvisol/146-165). Water stress and mineral deficiencies, including potassium, phosphorus, and magnesium, are major limiting factors to crop yields. The diagnostic survey also reveals that some practices can be used to correct the environment, particularly non-tillage with mulching and intercropping. The banana-bean system with no tillage and mulching is based on Conservation Agriculture, in particular the direct seeding mulch-based cropping (DMC). Using this system generates an increase in yield, except in the Acrisol, a "non-responsive soil" where the lack of response is linked to an extremely low fertility level requiring improvement of basic soil properties such as CEC, through the supply of organic matter. The yield for Ferralsol and Nitisol increases in ratio 1:1.6 to 1:5, depending on the type of straw, the most dramatic effect being recorded under Tripsacum mulch (ratio 1:3 to 1:5). However, the increase in yield was not significant in the least altered soils (Cambisol, Fluvisol). Overall productivity of the banana-bean system is high under Tripsacum. It increases by 82% for 50% and 25%, respectively under banana residues and Hyparrhenia. Yield increases underlie increased mineral exports, which lead to a decrease in soil nutrient content, primarily in potassium and phosphorus. This short-term negative assessment raises the question of the sustainability of the system. As a result, the increase in banana yield is due to an improvement in the CEC, the preservation of soil moisture and the correction of mineral deficiencies. The only realistic way to attain the cultural potential in a sustainable way in the African Great Lakes Region lies in the integrated soil fertility management through the supply of organic materials and mineral nutrients associated with mulching practices.
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Bizimana, S. (2018). L’agriculture de conservation peut-elle améliorer la fertilité des sols et la productivité des systèmes bananiers en Région des Grands Lacs ? https://hdl.handle.net/2078.5/127429