Tillage and Irrigation Requirements of Sorghum (<i>Sorghum bicolor</i> L.) at Hamelmalo, Anseba Region of Eritrea

Abstract

Most Eritrean farmers do not adopt soil conservation measures and till even sloppy fields 2-4 times for planting sorghum (Sorghum bicolor L.) with a view to facilitate rainwater intake. Field experiments were conducted at Hamelmalo to optimize tillage and irrigation requirements of sorghum in loamy sand. Tillage treatments were conventional tillage (4 times) on existing slopes (CTf), conventional tillage on managed plots (terraced) with residue (CTm + R) and without residue (CTm − R), reduced tillage (single tillage 4 days after heavy rainfall) on managed plots with residue (RTm + R) and without residue (RTm − R) and no tillage (direct planting) on managed plots with residue (NTm + R) and without residue (NTm − R) randomized in four replications. Tillage in CTm and CTf was same. Experiment was repeated in year II along with a new experiment in split plot design with same tillage treatments in main plots and 4 irrigation treatments in subplots in 3 replications. Irrigation treatments were rainfed (I0), 70 mm irrigation at 50% depletion of soil moisture in CTm − R from 1 m profile after end of monsoon (I 1), 70 mm irrigation 7 days after irrigation in I 1 (I 2), and 70 mm irrigation 7 days after irrigation in I 2 (I 3). Bulk density increased and infiltration rates decreased by harvesting due to tillage but changes were lower in residue plots of NT and RT than CT. Optimum soil moisture for emergence of sorghum was within 0.145 ± 0.002 m 3 m −3 at which soil strength was well below critical level for root growth. Soil strength in tilled layer due to intermittent wetting and drying following planting exceeded 2000 k Pa when dried below 0.143 m 3 m −3 moisture. Soil profile in CTf did not recharge by rainfall even by end of the rainy season, whereas it was fully wetted in level and terraced plots. Conservation measures resulted 80-150 mm of residual moisture per 2 m of soil profile at sorghum harvesting. Residual moisture was relatively more in residue and irrigated plots than in nonresidue and CTf plots. Soil bunding and levelling alone raised sorghum yields in RT + R to 2887 kg ha −1 under rainfed and 3980 kg ha −1 under 70 mm irrigation 21 days after last rainfall of the season (I 1). Corresponding yields in CTf were 501 kg ha −1 under rainfed and 1161 kg ha −1 under irrigation. Single

Factors Influencing Soil and Water Conservation Adoption in Basheri, Gheshnashm and Shmangus Laelai, Eritrea

“…Basheri: Basheri village is located in zoba Anseba, sub-zoba Hamelmalo along the Keren-Nakfa road; 13 Km north of the Keren town. The area belongs to the arid lowlands agro ecological zone (AEZ) of Eritrea having an average annual rainfall of 414.13 mm (average past 15 years), potential evapotranspiration rate of 1800 -2000 mm/year [12] and average annual temperature of 25 0 C; with the highest mean monthly temperature of 36.2 0 C in May and the lowest 11.0 0 C in January [19]. Basheri village has 215 households with a total population of around 1500.…”

Optimizing Tillage and Irrigation Requirements of Sorghum in Sorghum-Pigeonpea Intercrop in Hamelmalo Region of Eritrea

“…However, 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]. Water stress at vegetative stage alone reduced sorghum yields more than 36% and that during boot to reproductive stages more than 55% [11].…”

“…Rainfed sorghum is open to serious risks due to water stress during critical growth stages and agricultural droughts. Assured sorghum yields of about 4 t•ha −1 were possible by irrigating once in the terraced plots leaving significant amount of residual soil moisture [4] [6]. Intercropping of pigeonpea would be step towards achieving food security and soil quality improvements.…”

“…Soils of Anseba region are deep alluvium, medium to coarser in texture but rainwater rapidly runs off due to highly sloping traditional cultivated fields and that infiltrating percolates beyond the crop root zone in the terraced fields [3] [4] accelerating agricultural droughts. About 80 -150 mm residual moisture per 2 m of soil profile was observed at sorghum harvesting in the well managed watersheds ensuing zero runoff [4]- [6]. Considerable residual soil moisture at sorghum harvesting in managed watersheds provided opportunity for growing a legume intercrop like pigeonpea of shorter duration with sorghum that could survive on the residual moisture [4].…”