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

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 nu-trient uptake and conversion of cotton-based intercropping.In this paper,the uptake and conversion efficiency of nitrogen(N),phos-phorus(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 sys-tems.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 sys-tems increased N uptake by the range of 18%~74%.Also,compared with corresponding weighted mean of monocultured crops,cot-ton/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 corre-sponding 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 corre-sponding 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 ad-vantage.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.