ROLE OF CONTINUOUS WHEAT AND AMENDMENTS IN AMELIORATING AN ARTIFICIALLY ERODED DARK BROWN CHERNOZEMIC SOIL UNDER DRYLAND CONDITIONS

Complete loss of topsoil resulting from erosion or other causes genera lly results in reduced crop yield. To determine, under dryland conditi ons, the effect of loss of various amounts of soil and of various amen dment practices suitable for use under a cereal production program on soil properties and crop yields, a field was artificially eroded durin g cut and fill of land-levelling in 1957. Continuous cropping to barle y for 7 yr was followed by a wheat-fallow rotation for 22 yr. A contin uous wheat experiment was conducted from 1987 to 1991 to determine the effects of five fertility amendments on restoring the productivity to soil from which 10-20 cm and 46+ cm of soil had been removed. In 1990 , a below-average precipitation year, after 33 yr and 23 crops, yields from the unfertilized 46+ cm eroded field were only 44% of the yields from the uneroded field. However, with the increased precipitation in 1991 this value was 66%. A one-time topsoil amendment was beneficial in the earlier stages of the experiment, but lost its effect as cultiv ation mixed it into the ''subsoil'' over time. Plot treatments with an nual applications of manure and high rates of fertilizer generally out -yielded the yields of the check plots of the uneroded treatment. Amen dment with straw + fertilizer was not very effective. Soil, once lost, is non-renewable without amendments within the working lifetime of th e producer.