Tillage and drainage management of clay soils for the continuous production of annual crops under rainfed conditions in the humid tropics
Keywords:Tillage, Clay soils, Maize, Cowpea, Drainage
AbstractField studies were conducted to measure the response of maize (Zea mays L.) and cowpea [Vigna unguiculata (L.) Walp.] to tillage and no-tillage with and without mulch on the heavy fine-textured Onverwagt clay of Guyana and the lighter textured Cunupia clay of Trinidad. Tillage treatments were imposed on 9-m, 6-m, and 3-m-wide cambered beds to assess the effect of field drainage. The aim was to develop a tillage management system from the results of the study that would allow all-year production of annual crops on clay soils under rainfed conditions of Guyana, which has a major and minor wet season annually, and of Trinidad, which has one intense wet season. In the major wet season in Guyana, germination of maize on Onverwagt clay was high on 3-m, 6-m, and 9-m-wide beds when the soil was tilled, but it was significantly reduced (P = 0.05) on 6-m and 9-m-beds that were not tilled. Germination did not always reflect plant population at harvest. There was less seedling survival on the wider 6-m and 9-m beds than on the 3-m beds and, in particular, when the soil was not tilled. This influenced cob yields at harvest. Cob yields on 9-m beds of both till and no-till were low, and were generally the highest on 3-m beds. Tillage of 6-m beds also produced high yields. The amount of rainfall during the crop also influenced plant growth parameters and cob yield. In the minor wet season, 9-m-wide beds on Onverwagt clay were not as detrimental to plant survival and cob yield, and tillage significantly (P = 0.01) increased cob yields. When cowpea was grown on 3-m-wide beds on Onverwagt clay, there were no significant differences in plant growth parameters and grain yield in the major and minor wet seasons, and between till and no-till. On the lighter Cunupia clay, cob yield was highly depressed (P = 0.01) by no-tillage on 9-m beds when the rainfall was intense but it was only significantly depressed (P = 0.05) when the rainfall was less intense. When cowpea was grown on 6-m beds on Cunupia clay, there were no significant differences in plant parameters including yield between till and no-till. The results indicated that the appropriate selection of crop, bed width, and tillage management can permit annual crops to be grown all year round on heavy and light textured clay soils under the rainfall regimes of Guyana and Trinidad.