THE EFFECT OF VARIOUS RESIDUE MULCH TILLAGE COMBINATIONS ON SOIL PHYSICAL CONDITIONS AND PERFORMANCE OF IRRIGATED COTTON

Cotton is a major irrigated summer field crop in Israel, and is common ly grown in the same field far 3-5 years in succession, There is only a narrow time window between harvest and early rains for pest control by means of clearing the land surface of residues, and to perform prep aratory tillage, The time available may be insufficient to achieve thi s with the conventional deep plowing tillage system, and some operatio ns may have to be carried out on moist soil between rainfall events. I n response to indications of decreasing yield due to compaction, vario us limited-tillage systems in permanent traffic lanes have been develo ped, culminating in a machine that performs all residue-disposal and t illage operations in a single pass through the field. A comparison of several limited-traffic and conventional practices was carried out for 2 years on a loessial silt loam (Calcic Haploxeralf). It was found th at both soil condition and yield were worst in the two treatments comm only used by farmers: deep plowing and deep incorporation of residues with the combination machine, Tillage effects were dominant, masking a ny effect of residue amount and disposal method. Large differences wer e found between the zones of the permanent wheel track treatments, as were cyclic changes in soil condition reflecting the seasonal sequence of tillage operations. Some cumulative compaction occurred, due mainl y to a gradual widening, of the wheel tracks rather than to repeated p asses in the original rut. The findings of this work show that the opt imal choice is to replace the previously preferred field practices by shallow slot-mulching with simultaneous subsoiling by the combination machine, which meets the sanitation requirements, maintains satisfacto ry yields and saves energy and labor.