Can Conservation Agriculture Technologies Mitigate Intra-Seasonal Drought Effects on Crop Yields in Steep Lands? Case of the Southern Uluguru Mountains, Tanzania

Abstract

This study was conducted in the 2015 and 2015/16 rain seasons at Kolero village, in the southern Uluguru Mountains, Tanzania. The aim was to investigate the effectiveness of different Conservation Agriculture (CA) practices on runoff control and soil moisture retention as well as its implication on rainfall use efficiency (RUE) and crop production and environmental conservation on the steep slopes. Two factors (tillage practice and soil surface cover mulches, i.e. crop residues and cover crops) each at three levels, were combined to form a 3 x 3 factorial experiment and tested in a Randomized Complete Block Design (RCBD) with three replications each. Levels of tillage were shallow tillage, zero tillage and strip tillage; and those for cover crop were slash and burn, lablab and cowpea cover crops with residue retention. Moisture readings were taken at 0 - 20 cm, 20 - 40 cm, 40 – 60 cm, 60 – 80 cm and 80 - 100 cm soil depths. Results showed that there were significant differences (P<0.05) among treatments in runoff, at which conventional tillage recorded 26.7% and 42.2% runoff for 2015 and 2015/16 rain seasons respectively, while CA treatments had between 3.5 to 22.2 % runoff. There was also numerically higher volumetric moisture content for most of the cropping months in CA treatments at 0 to 45 cm soil depths. Soil temperature was high in conventional practices from 0 to 100 cm soil depths as compared to CA treatment for most of the cropping months. Conventional practice also showed significant difference (P<0.05) as it recorded the lowest RUE (4.2 kg ha^-1 mm^-1) compared to CA treatments whose RUE ranged between 5.8 and 6.3 kg ha^-1 mm^-1 for the 2015/16 rain season which had erratic rainfall and prolonged dry spells. Most CA treatments were observed to be more effective in runoff control, moisture conservation as well as provision of high RUE at fragile foothills of southern Uluguru Mountains. CA treatments have shown to be effective in mitigating intra-season dry spells.

Keywords: conservation agriculture, runoff, soil moisture, soil temperature, slash and burn