Agro-farming systems determine phosphorus budget characteristics at the farm and catchment scales in subtropical China

Abstract

Agricultural and economic activities may profoundly determine phosphorus (P) budget characteristics that affect environmental quality; therefore, P budget characteristics were investigated at the farm and catchment scales, and the total-phosphorus (TP) concentrations in stream water were observed to examine their relationships in eight Chinese subtropical catchments. The results showed that chemical fertilizer accounted for 67–76% of the total P input and cereal grain comprised of 60–62% of the output in the planting farms, while animal feed and animal product accounted for 62–95 and 48–71% in the planting–livestock farms and livestock farms, respectively, indicating that agro-farming systems determined the P budget characteristics at the farm scale. The P input, output, and surplus intensities linearly increased with agricultural incomes in the agro-farming systems, suggesting that economic activities greatly affected the P budget characteristics at the farm scale. The catchment P budget characteristics were largely shaped by the characteristics at the farm scale; the planting–livestock farm proportion was negatively correlated (R2 > 0.55) while the livestock farm proportion was positively correlated (R2 > 0.59) with catchment P budget items. These effects on catchment P budget characteristics greatly deteriorated stream water quality; both the TP concentrations and loadings in stream water were significantly correlated to catchment P input, output, and surplus intensities. Considering the higher economic benefits and lower P input and surplus intensities due to the closed P cycle loop between cropping and husbandry, planting–livestock system should be promoted at the farm scale to protect catchment water environmental quality in subtropical China.