Abstract
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.
Highlights
Growth Pattern of Sorghum and Pigeonpea Sorghum vegetative growth was relatively better in conventional tillage (CT) and reduced tillage (RT) plots than in zero tillage (ZT), perhaps because ZT was more affected by weeds in the initial establishment period
Variety planted in the experiment appears to be wilder type because flowering and maturity continued for several months after sorghum harvesting
2) About 80% sorghum roots in sorghum-pigeonpea intercrop are within 0.6 m profile whereas >75% pigeonpea roots are below 0.60 m indicating weak competition
Summary
Moench) is a major crop of Eritrea contributing about 46% of the total cereal production [1]. Its productivity has been below 0.6 t∙ha−1 due to improper rainwater management, lack of available soil moisture at grain filling stages, low inputs and poor soil and crop management [2] [3]. Sorghum yields could be optimized through adoption of rainwater management and conservation tillage practices [3]-[6] and minimizing risks due to agricultural droughts through supplemental irrigations [7]-[10]. Sivakumar et al [12] observed that two irrigations increased sorghum yields from 2430 - 5990 kg∙ha−1. Single 50 mm irrigation from runoff harvesting in the watershed increased sorghum yields from 25703570 kg∙ha−1 [13] [14]
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