Effects of phosphorus and four tillage mulch systems on the physico-chemical properties of an ultisol in Eastern Nigeria

Abstract

The effects of four tillage-mulch systems on some soil physico-chemical properties of an Ultisol under cowpea (Vigna unguiculata) cultivation were investigated from the year 2004 to 2005. The tillage-mulch treatments consisted of tilled-mulched (TM), untilled-mulched (UM), tilled-unmulched (TU), and untilled-unmulched (UU) (control) plot. Differences in the infiltration rate and bulk density of the treated plots were significant at P<0.05. Micro-porosity, macro-porosity, total porosity, mean weight diameter of water stable aggregates and saturated hydraulic conductivity, however, did not show significance. The infiltration rates of the TM, TU, UM and UU treated plots were 0.022, 0.016, 0.012, 0.010 and 0.027, 0.019, 0.012 and 0.010cm sec-1 for the first and second years, respectively. The infiltration rates on tilled plots significantly (p<0.05) increased and doubled that of the untilled plots, while mulching significantly (p<0.05) increased infiltration rates on tilled plot. The TM plots increased by 23%, TU by 19% while the UM and UU plots were stable in their infiltration rates from the first to the second year. Seventeen percent of this increase was attributed to mulching while 83% to tillage. The bulk density of untilled plots (1.55 – 1.59 g cm^-3) were higher (p <0.05) than that of tilled plots (1.26 – 1.49 g cm^-3) while mulching tended to significantly increase bulk density on tilled plots. The mulched plots had high available P (30.54 – 40.88 mg kg^-1) compared to the control plot (25.50 – 26.69 mg kg^-1), 9 weeks after phosphorus treatment. Available P in UM plots were higher than in the other plots. These variations in available P following the tillage-mulch treatments did not result in significant changes in the tissue P of cowpea at flowering.

> Agro-Science Vol. 6 (1) 2007: pp. 25-32