Effects of residual tied ridges on soil physical factors and sorghum yield in semi-arid central Tanzania.
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Date
2001
Journal Title
Journal ISSN
Volume Title
Publisher
Sokoine University of Agriculture
Abstract
With the increasing use of conservation tillage, many questions have been raised on many at harvest respectively. Tillage significantly (p=0.05) affected the soil surface the viability of using residual tied-ridging system. The reported field study was conducted in semi-arid central Tanzania on a continuing three year old tillage trial comprising No-till (Tl), Shallow tied ridges (T2) and deep tied ridges (T3) to study the effect of residual tied-ridges on soil physical and hydrological properties as well as sorghum grain yield. Land preparation involved the removal of crop residues from the previous season and a minimum maintenance of residual ridges. The test crop was sorghum cultivar Tegemeo. Investigated parameters include dry bulk density and cumulative infiltration which were determined before planting, at mid season and after harvest. Gravimetric soil moisture determinations at different soil depth were made on weekly basis. Measurements on soil surface roughness were made before and after every field operation and after every heavy rainstorm. Bulk densities were significantly (p=0.05) different between Tl and other treatments only at mid season within 0-10 cm soil layer. Total porosity values were not significantly different among tillage treatments during the study period. Weekly gravimetric soil profile moisture content (mm) in 0-50 cm soil layer was significantly (p=0.05) different between treatments on the 4th, 8th, and 17th week after planting. Profile moisture content variations of between 40.4 to 59.4 mm, 48.4 to 77.7 mm and 57.5 to 85.5 mm for Tl, T2 and T3 respectively were observed during the growing season. However, Tl had significantly (p=0.05) higher cumulative infiltration than T2 and T3 by 134.8 and 172.8 mm before planting, 764 and 845.5 mm at mid season and by 355 and 437 With the increasing use of conservation tillage, mm at harvest respectively. Tillage significantly (p=0.05) affected the soil surface roughness indices (SSRI) among treatments. SSRI variations of between 68.7 to 106.3 for Tl, 152.8 to 169.2 for T2 and 173.2 to 180.0 for T3 were observed. Moreover the SSRI decreased during the growing season. Percentage seedling emergence was significantly (p=0.05) higher in Tl by 5.7 and 14.2% than in T2 and T3 respectively. Nevertheless the crop stand at harvest was lower in Tl by 15.1 and 4.1% than in T2 and T3 respectively. T2 and T3 had significantly (p=0.05) higher grain yield by about 0.85 and 1.06 t/ha respectively. Grain yield was more than doubled by residual tied-ridges compared to the control which had a yield of
0.64t/ha. Residual tied ridges are thus a viable tillage system which can reduce tillage and ridging cost as well as increase sorghum grain yield in semi-arid areas.
Description
Dissertation
Keywords
Soil physical factors, Sorghum yield, Semi arid, Central Tanzania