Uptake and conversion efficiencies of NPK and corresponding contribution to yield advantage in cotton-based intercropping systems

Abstract

Cotton-based intercropping is a popular agronomic practice in Northwest China. This agronomic practice addresses the conflict in planting area/space between cereals and cotton. However, not sufficient knowledge exists on the yield advantage and nutrient uptake and conversion of cotton-based intercropping. In this paper, the uptake and conversion efficiency of nitrogen (N), phosphorus (P) and potassium (K) were assessed in several cotton-based intercropping systems, including cotton/peanut, cotton/soybean, cotton/chickpea, cotton/onion, cotton/radish and cotton/line-chilli intercropping systems, and the corresponding monocropping systems. Then yield advantage and nutrient uptake and conversion of cropping systems were determined. Compared with weighted mean of monocultured crops of sole cropping systems, cotton/peanut, cotton/chickpea, cotton/onion and cotton/radish intercropping systems increased N uptake by the range of 18%-74%. Also, compared with corresponding weighted mean of monocultured crops, cotton/soybean and cotton/chilli intercropping systems decreased N uptake by 10% and 34%, respectively. P uptake under intercropping systems of cotton/peanut, cotton/chickpea, cotton/onion, cotton/radish and cotton/soybean was higher than that under the corresponding sole cropping systems by 5%-104%. However, the reverse was the case for cotton/chill, where it was lower by 6%. About 20%-58% increase in K uptake was noted under cotton/peanut, cotton/onion and cotton/radish intercropping systems over the corresponding sole cropping systems. However, K uptake dropped by 19%-22% under cotton/soybean, cotton/chickpea and cotton/chilli intercropping systems over the corresponding sole cropping systems. Land equivalent ratios (LER) of cotton/chickpea, cotton/peanut, cotton/onion and cotton/radish intercropping systems were 1.02, 1.30, 1.12 and 1.68, respectively, indicating a significant yield advantage. However, LER of both cotton/soybean and cotton/chilli intercropping systems were 0.91 and 0.99, respectively, indicating no yield advantage. The contributions of the uptake efficiencies of N, P and K to LER were 0.41-0.82, 0.25-1.04 and 0.15-0.59 in cotton/peanut, cotton/onion and cotton/radish intercropping systems, respectively. The corresponding conversion efficiencies were -0.35--0.04, 0.03-0.14 and -0.16-0.01, respectively. Yield advantage of intercropping was mainly from enhanced nutrient uptake efficiency, and not from nutrient conversion efficiency.