Author(s)

Tesfalem Weldeslassie, Ramesh Prasad Tripathi^*, Woldeselassie Ogbazghi

Department of Land Resources and Environment, Hamelmalo Agricultural College, Keren, Eritrea.

Sorghum (Sorghum bicolor L. Moench) is cultivated as monocrop in Eritrea. Efforts were made to grow sorghum-pigeonpea (Cajanus cajan L. Millspp.) intercrop on the tillage, fertilizers and supplementary irrigations necessary for sorghum. Experiments were conducted in terraced fields at Hamelmalo during 2013-15 to evaluate growth and yield of sorghum-pigeonpea intercrop in split plot design with conventional tillage (CT), reduced tillage (RT) and zero tillage (ZT) in main plots and rainfed (I₀), 50% of full irrigation (I₁), 75% of full irrigation (I₂) and 100% of full irrigation (I₃) in subplots. All irrigations were stopped 15 days before sorghum maturity. Full irrigation was 60 mm applied at 50% depletion of available soil water in 1 m profile. Sorghum growth was faster than pigeonpea until 85 days from planting and pigeonpea growth accelerated only after sorghum harvesting. About 80% of sorghum roots were within 0.6 m profile but more than 75% of pigeonpea roots were below 0.60 m depth. This showed a weaker competition between the two crops for nutrients, water and light. Both grain and stover yields of sorghum were optimum in RT + I₂ during the 2 years. Highest grain yield was 6900 kg·ha^-1 in RT + I₃ in 2013, which was at par with that in RT + I₂. Mean residual soil moisture at sorghum harvesting was 74 mm·m^-1, which decreased to 8 mm·m^-1 by pigeonpea harvesting. Residual moisture was more in the irrigated than non-irrigated plots. Pigeonpea yields were optimum (1363 kg·ha^-1) in RT + I₃ and lowest (297 kg·ha^-1) in ZT + I₀. Average water use by sorghum-pigeonpea was 374 mm by sorghum harvesting and 438 mm by pigeonpea harvesting, producing total sorghum equivalent yield of 7475 kg·ha^-1. This raised average water use efficiency from 12.6 kg·ha^-1·mm^-1 at sorghum harvesting to 17.1 kg·ha^-1·mm^-1 at pigeonpea harvesting. Benefit was doubled at 50% of full irrigation and >4 times at 75% of full irrigation.

Residual Soil Moisture, Sorghum-Pigeonpea Intercrop, Supplementary Irrigation, Water Use Efficiency

Weldeslassie, T. , Tripathi, R. and Ogbazghi, W. (2016) Optimizing Tillage and Irrigation Requirements of Sorghum in Sorghum-Pigeonpea Intercrop in Hamelmalo Region of Eritrea. Journal of Geoscience and Environment Protection, 4, 63-73. doi: 10.4236/gep.2016.44009.