Carbon dynamics and fertility in biochar-amended soils with excessive compost application

Abstract

In Taiwan, farmers often apply excessive compost to ensure adequate crop yield in frequent tillage, highly weathered, and lower fertility soils. The potential of biochar (BC) to decrease soil C mineralization and improve soil nutrient availability in excessive compost application soil is promising, but under-examined. To test this, a 434-day incubation experiment of in vitro C mineralization kinetics was conducted. We added 0%, 0.5%, 1.0%, and 2.0% (w/w) woody BC composed of lead tree (Leucaena leucocephala (Lam.) de. Wit) to one Oxisol and two Inceptisols in Taiwan. In each treatment, 5% swine manure compost was added to serve as excessive application. The results indicated that soil type strongly influences the impact of BC addition on soil carbon mineralization potential. Respiration per unit of total organic carbon (total mineralization coefficient) of the three studied soils significantly decreased with increase in BC addition. Principal component analysis suggested that to retain more plant nutrients in addition to the effects of carbon sequestration, farmers could use locally produced biochars and composts in highly weathered and highly frequent tillage soil. Adding 0.5% woody BC to Taiwan rural soils should be reasonable and appropriate.