Effect of deficit irrigation on wheat and opportunities of growing wheat on residual soil moisture in southeast Zimbabwe

Soil moisture from six sites in Romwe was measured at the end of the wet season (April) and at the end of the dry season (October) and the available water calculated. Results from a variety by irrigation trial run at Chiredzi Research Station for two seasons was used to assess the possibility of growing wheat on residual soil moisture in Romwe. Six wheat genotypes (P1, P2, Pote, Deka, Nata and Ruya) were grown under three irrigation regimes at Chiredzi Research Station during the 1996 and 1997 winter seasons. The irrigation regimes used were supplying irrigation water according to the crop water requirements, supplying three quarters of the crop water requirements and half of the crop water requirements at each irrigation day. Applying three quarters and half of the crop water requirements resulted in a yield decrease of 12 and 20% in 1996 and 7 and 20% in 1997 season, respectively. P2 gave the highest yields on average for the two seasons and was the least affected by deficit irrigation. However, Deka gave the least decrease in yield when the three-quarters and half water requirements were supplied. Four of the sites in Romwe, where residual soil moisture was measured, had more than half the water required to meet the crop water requirements of wheat.