A meta-analysis of long-term effects of conservation agriculture on maize grain yield under rain-fed conditions

Abstract

Conservation agriculture involves reduced tillage, permanent soil cover and crop rotations to enhance soil fertility and to supply food from a dwindling land resource. Recently, conservation agriculture has been promoted in Southern Africa, mainly for maize-based farming systems. However, maize yields under rain-fed conditions are often variable. There is therefore a need to identify factors that influence crop yield under conservation agriculture and rain-fed conditions. Here, we studied maize grain yield data from experiments lasting 5 years and more under rain-fed conditions. We assessed the effect of long-term tillage and residue retention on maize grain yield under contrasting soil textures, nitrogen input and climate. Yield variability was measured by stability analysis. Our results show an increase in maize yield over time with conservation agriculture practices that include rotation and high input use in low rainfall areas. But we observed no difference in system stability under those conditions. We observed a strong relationship between maize grain yield and annual rainfall. Our meta-analysis gave the following findings: (1) 92% of the data show that mulch cover in high rainfall areas leads to lower yields due to waterlogging; (2) 85% of data show that soil texture is important in the temporal development of conservation agriculture effects, improved yields are likely on well-drained soils; (3) 73% of the data show that conservation agriculture practices require high inputs especially N for improved yield; (4) 63% of data show that increased yields are obtained with rotation but calculations often do not include the variations in rainfall within and between seasons; (5) 56% of the data show that reduced tillage with no mulch cover leads to lower yields in semi-arid areas; and (6) when adequate fertiliser is available, rainfall is the most important determinant of yield in southern Africa. It is clear from our results that conservation agriculture needs to be targeted and adapted to specific biophysical conditions for improved impact.

Conservation agriculture in Southern Africa: Advances in knowledge

“…In some environments the benefits of CA started after 1-2 seasons, whereas in other environments the benefits required more seasons for effects to build up 23,94 , which is in agreement with a recent meta-analysis 96 . For example, in the high-rainfall environment of Zidyana EPA, Malawi, characterized by sandy loam soils, substantial maize yield benefits were obtained after five seasons 28 .…”

“…However, these past researches were largely conducted within experimental stations and did not take into account socio-economic constraints in real farm situations that could hinder the widespread adoption of CA. Recently, more studies reporting results from onfarm and on-station trials have been published concentrating on some of the above-mentioned challenges and constraints 28,37,68,73,86,94,96,97,99,101,102,104,[113][114][115][116] .…”

Studies on impact of nutrient management and tillage practices on yield attributes and yield on gram – maize cropping sequence

“…However in rest of treatment combinations of management practice and tillage there was increase in yield from first year to third year respectively. The most astonished results was obtained under control treatment in which the yield decline from first year to third year was 800% and no yield was reported in third year, the results are corroborated by the findings of Rusinamhodzi et al (2011). It might be due to fact that due to non application of any source of nutrient(organic and inorganic) the pathogens mainly fungus attack the plant root and used as source of nutrients causes decline and no yield.…”

Long‐Term Tillage on Yield and Water Use of Grain Sorghum and Winter Wheat

“…been in place (Rusinamhodzi et al, 2011). Results of other studies have also suggested a crop, soil, and general location specifi c yield benefi t from NT compared with CT for sorghum, wheat, and other crops in the United States, specifi cally in the Great Plains region (Norwood et al, 1990;Norwood, 1992;Unger, 1994;Schlegel et al, 1999;Toliver et al, 2012;Farooq et al, 2011).…”