Soil properties and vegetable production with organic mulch and no-tillage system.

Organic mulch was formed by mowing wheat straw and hairy vetch in a no-tillage field. Soil temperature under the organic mulch was constant, and the organic mulch decreased soil temperature in summer and early autumn and increased it in middle and late autumn compared with a bare and tilled field. The pF was maintained at 1.5-1.8 even in the dry weather of August. Though much more release of inorganic nitrogen in the soil covered with organic mulch was recognized than in the bare and tilled field, there was no definite difference in the quantity of inorganic nitrogen released between the wheat straw and the hairy vetch mulch. Nitrogen concentration in lettuce produced in the hairy vetch mulch field was a little higher than that of lettuce in the bare and tilled field in autumn, 1995. Weed growth was suppressed effectively in the field covered with hairy vetch, and weed control was 53% in the wheat straw mulch field compared with that in the bare and tilled field. The yield of leaf lettuce (butter head), tomato and pod soybean in the hairy vetch mulch field was higher than in the wheat straw mulch field or the bare and tilled field.