Conservation agriculture and tillage effects on soil organic matter and residual moisture content in selected upland crop production systems in the Philippines

This study aimed to analyze the influence of conservation agriculture and tillage on soil or-ganic matter and residual moisture content in selected upland crop production systems in the Philippines. Conservation agriculture is based on the principles of minimum soil disturbance, continuous mulch cover and diversified species rotation. Six Conservation Agriculture Pro-duction Systems (CAPS) treatments in the form of cropping patterns with different cover crops under two fertility levels including plow-based or tilled system serving as control were established and laid out in a randomized complete block design in a typical upland agricul-tural producing area in southern Philippines. Composite soil samples were collected at the uppermost soil layer with a depth of 0-5 cm and were analyzed for soil organic matter con-tent. The residual soil moisture content was also measured at the various plots of the CAPS treatments using time domain reflectometry (TDR). Results showed that the soil organic mat-ter for all CAPS treatments (T1 to T5) was generally higher than under T6 (plow-based) after three years of cropping. After three cropping seasons, treatment T2 (Maize+stylosanthes guianensis-stylosanthes guianensis-fallow) exhibited the highest soil organic matter at the uppermost soil layer (0-5 cm). Linear regression analysis showed that the soil organic matter at the uppermost soil layer under plow-based system declined over time for both fertility lev-els. Under a high fertility level, the soil organic matter at the uppermost layer for all CAPS treatments T1 to T5 all exhibited a positive change over time, with T2 (Maize+stylosanthes guianensis-stylosanthes guianensis-fallow) exhibiting the highest rate of increase. Under a moderate fertility level, the soil organic matter for CAPS treatments increased over time with T5 (cassava+Stylosanthes guianensis) exhibiting the highest rate of increase. Analysis of variance of the residual moisture after one, two and three cropping seasons showed that the plots under conservation agriculture have significantly higher residual moisture content than under plow-based system with CAPS treatment T2 exhibiting the highest residual moisture content. Results of this study suggest that conservation agriculture has a positive impact on soil quality in terms of soil organic matter and residual moisture content while tillage systems negatively impact these soil quality parameters.

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