Animal powered tillage translocated soil affects nutrient dynamics and soil properties at Claveria, Philippines

ABSTRACT:

Intensive tillage in a humid tropical setting on uplands in Claveria, Philippines moves soil downslope, often creating unfavorable soil conditions for crop production. This field study, conducted on Oxisols with slope gradients ranging from 16–22%, evaluated nutrient dynamics for four ox-powered contour tillage systems: 1.) contour moldboard plowing (CMP); 2.) contourridge tillage (CRT); 3.) contour natural grass barrier strips plus contour moldboard plowing (GCMP); and 4.) contour natural grass barrier strips plus contour ridge tillage (GCRT). The four management systems (treatments) were replicated three times on two sites. Eight corn (Zea mays L) crops were grown from 1992 to 1996 Corn residues, vegetative materials, and inorganic fertilizers (80 kg N, 30 kg P, and 30 kg K ha⁻¹) were applied uniformly to all systems. Lime at 3 Mg ha⁻¹ was applied in 1992. Soil sampling was conducted within plots initially, and in 1996 was systematic at equally divided compartments along transects. Overall, from 1992 to 1996 the concentration of total C slightly increased, total N slightly decreased, and extractable Ca, K, P, Cu, and Zn increased significantly in all systems. During the four year period, generally, the concentration gradients of extractable P, K and Ca within treatments became steeper, with the higher concentrations occurring at the lower elevation of the CRT and CMP plots and at the lower elevation of individual terraces of GCMP and GCRT plots. In contrast, concentration gradients for Cu and Zn increased linearly from the lower to higher elevation. Soil pH immediately downslope from the grass strips was significantly lower compared to pH in the grass strips. The changes in pH and chemical concentration gradients across the plots and terraces are attributed primarily to tillage translocated soil downslope due to moldboard plowing. Installation of contour grass barrier strips in conjunction with ridge tillage reduced the rate of soil translocation and, thus, the rate of chemical gradient change.