SOIL WATER CONSERVATION, GROWTH, YIELD AND WATER USE EFFICIENCY OF SORGHUM AS AFFECTED BY LAND CONFIGURATION AND WOOD-SHAVINGS MULCH IN SEMI-ARID NORTHEAST NIGERIA

Abstract

Water is perhaps the most important single factor that limits crop production in the semi-arid northeast of Nigeria. A four-year field experiment was therefore initiated in 1999 to evaluate the influence of land configuration practices with or without wood-shavings mulch on water conservation, yield and water use efficiency (WUE) of sorghum. The experimental treatments consisted of flat bed (FB), open ridging (OR), tied ridging (TR), FB + mulch (FBM), OR + mulch (ORM), and TR + mulch (TRM). Ridge heights were 15 to 20 cm and furrows were left open (for OR and ORM) or tied (for TR and TRM). Wood-shavings mulch was used at the rate of 5 t ha⁻¹ in 1999, but this was increased to 10 t ha⁻¹ in subsequent years to ensure adequate soil coverage. Differences in soil water storage at various sampling dates were significant only in some cases in each year, but trends were towards greater soil water storage in the mulched treatments than in the non-mulched treatments, irrespective of tillage method. Growth parameters (plant height and leaf area index) indicated significant differences between treatments on only some measurement dates in each year. Sorghum water use varied significantly between years and treatments. Seasonal water use was greater with FBM, ORM and TRM than with the FB treatment in all cropping seasons. Averaged over the four-year period, mean increases in grain yield relative to the FB treatment were 16 % for OR, 25 % for TR, 77 % for FBM, 50 % for ORM and 57 % for TRM. Pooled across the experimental years, the WUE (ET) of FB, OR, TR, FBM, ORM and TRM were 1.95, 2.12, 2.13, 2.74, 2.36 and 2.48 kg ha⁻¹ mm⁻¹ respectively. The corresponding WUE(R) values for these treatments were 1.26, 1.46, 1.56, 2.22, 1.88 and 1.97 kg ha⁻¹ mm⁻¹ respectively. It is concluded that combining the practice of flat bed cultivation with mulching may eliminate the need for ridging in increasing the productivity of sorghum grain in semi-arid northeast Nigeria.