Photosynthetic and yield responses of rotating planting strips and reducing nitrogen fertilizer application in maize-peanut intercropping in dry farming areas

Improving cropping systems together with suitable agronomic management practices can maintain dry farming productivity and reduce water competition with low N inputs. The objective of the study was to determine the photosynthetic and yield responses of maize and peanut under six treatments: sole maize, sole peanut, maize-peanut intercropping, maize-peanut rotation-intercropping, 20% and 40% N reductions for maize in the maize-peanut rotation-intercropping. Maize-peanut intercropping had no land-use advantage. Intercropped peanut is limited in carboxylation rates and electron transport rate (ETR), leading to a decrease in hundred-grain weight (HGW) and an increase in blighted pods number per plant (N-BP). Intercropped peanut adapts to light stress by decreasing light saturation point (I-sat) and light compensation point (I-comp) and increasing the electron transport efficiency. Intercropped maize showed an increase in maximum photosynthetic rate (Pn(max)) and I-comp due to a combination of improved intercellular CO2 concentration, carboxylation rates, PSII photochemical quantum efficiency, and ETR. Compare to maize-peanut intercropping, maize-peanut rotation-intercropping alleviated the continuous crop barriers of intercropped border row peanut by improving carboxylation rates, electron transport efficiency and decreasing I-sat, thereby increasing its HGW and N-BP. More importantly, the land equivalent ratio of maize-peanut rotation-intercropping in the second and third planting years were 1.05 and 1.07, respectively, showing obvious land use advantages. A 20% N reduction for maize in maize-peanut rotation-intercropping does not affect photosynthetic character and yield for intercropped crops. However, a 40% N reduction decreased significantly the carboxylation rates, ETR, I-comp and Pn(max) of intercropped maize, thereby reducing in a 14.83% HGW and 5.75% lower grain number per spike, and making land-use efficiency negative.