IRRIGATION SCHEDULING FOR SWEET MAIZE RELATIVE TO SOIL COMPACTION CONDITIONS

A factorial experiment was conducted in a greenhouse to investigate th e effect of three irrigation intervals (I = 1, 2 and 3 d) and three wa ter application depths (D = 0.5, 1.0 and 1.5 cm) on the growth and dev elopment of sweet maize planted on a sandy loam soil contained in core s (20cm internal diameter and 21cm long) and compacted using 5, 15 and 25 equivalent Proctor hammer blows. The equivalent Proctor blows were worked out based on the ratio of the cross-sectional area of the soil cores (314cm(2)) used in the experiment to that of the Proctor compac tion moulds (82cm(2)) normally used as standard in compaction experime nts. The treatment (I = 2 d, D = 1.0 cm) produced the highest values o f mass of plant dry matter, plant height, shoot diameter, leaf area an d crop water-use efficiency followed by the treatment with the recomme nded irrigation interval and depth (I = 3 d, D = 1.5 cm). This was par ticularly true for the 5 and 15 equivalent Proctor blows. Mean values of these plant parameters for the three experimental factors, declined significantly (P = 0.01) with soil compaction, ranging from 7% for th e plant height to 41% for the dry matter as the compaction level incre ased from low (5 blows) to severe (25 blows). Plants irrigated at 2 d intervals had the highest mean values followed by those irrigated at 3 d and Id intervals in that order. Mean values of plant parameters imp roved with increasing water depths but the increases were only signifi cant (P = 0.01) for the plant dry matter and the water-use efficiency parameters. There were significant interactions among the three factor s studied and these were used to describe the effects of compaction an d irrigation regime on the measured plant growth parameters. Results s howed that the adverse effects of compaction on plant development can be decreased by reducing the irrigation interval, but at the same time reducing the water applied in proportion to the shorter irrigation in terval. (C) 1995 Silsoe Research Institute