Variability of Soil Quality Parameters Under Conservation Agriculture Production Systems in the Philippines.

Conservation agriculture is a promising biological engineering approach to soil conservation based on the principles of minimum soil disturbance, continuous mulch cover and diverse crop species. This study was conducted to determine and analyze the variability of soil quality under conservation agriculture production systems (CAPS) in the Philippines. Six CAPS treatments in the form of cropping patterns with different cover crops under two fertility levels including plow-based system were established and laid out in a randomized complete block design in a typical upland agricultural producing area in Claveria, Misamis Oriental, Philippines. Soil sampling was performed at three depths (0-5 cm, 5-10 cm and 15-30 cm) at the experimental site in 2010, 2011 and 2012. The soil samples collected were brought to University of the Philippines Los Baños for physical and chemical analysis. The observed values of bulk density, soil organic matter, soil nitrogen, soil phosphorus and soil pH at various CAPS treatments were consequently analyzed. The residual soil moisture content was also measured at the various plots of the CAPS treatments at the site using time domain reflectometry (TDR). Results showed that differences in soil quality parameter values were observed over time and at various depths for the various CAPS treatments. The soil organic matter at the uppermost soil layer (0-5 cm) did not exhibit a well-defined pattern of temporal variation for most of the CAPS treatments although the organic matter under conventional plow-based system appeared to decline slightly over time. Both soil nitrogen and phosphorus concentrations in all CAPS treatments were generally higher in the upper soil layers (0-15 cm) than in the deeper soil layers (15 to 30 cm) under the two fertility levels. The soil bulk density remained practically the same as the baseline conditions for all soil layers. Analysis of variance of the residual moisture during the dry month showed that the plots under conservation agriculture have significantly higher residual moisture content than under conventional plow-based system with the CAPS treatment   maize+Stylosanthes guianensis- Stylosanthes guianensis- fallow exhibiting the highest residual moisture content level. Continuous soil quality monitoring is necessary to generate additional empirical evidence on the impact of conservation agriculture on soil quality. Ultimately, all these findings could serve as basis for potential upscaling and policy formulation for soil resources conservation and sustainable agriculture in the Philippines.