On-farm assessment of the phosphorus balance of paddy soil fertilized with cow dung compost in mixed crop–livestock systems and with rice straw in conventional practice in Yamagata, Japan

Abstract

ABSTRACT Rice straw (RS) and cow dung compost (CDC) are good sources of phosphorus (P) to support rice production. Our previous research found that CDC application in mixed crop-livestock systems supplied more total P to the paddy soil than RS, but available P did not differ significantly between the CDC and RS fields. To explain these results, we investigated the soil total P and soil P balance in RS and CDC fields. From the 79 paddy fields managed by farmers in Mamurogawa, Yamagata, Japan, which were investigated in previous research, we selected 10 pairs of adjacent RS and CDC fields, then measured soil total P, P inputs (RS or CDC and fertilizer), and P outputs (plant uptake and leaching), and calculated the resulting soil P balance. The result showed that soil total P did not differ significantly between treatments. The higher P input from CDC would let farmers apply less fertilizer P in CDC fields than in RS fields, but there was no significant difference in total P input between treatments. Plant P uptake and leaching did not differ significantly between treatments. The soil P balance was positive (i.e., net P accumulation) and did not differ significantly between treatments. The lack of differences in the total P input, total P output, and soil P balance between treatments explains the non-significant differences in soil total P and available P.