[Effects of row spacing configuration on root distribution and interspecific competition in an apricot-alfalfa...

We analyzed the effects of row spacing configuration on interspecific competition and resource utilization under five treatments: monoculture Prunus armeniaca (X), monoculture Medicago sativa (A, 20 cm row spacing), monoculture M. sativa (B, 30 cm row spacing), P. armeniaca-M. sativa intercropping (JA, 20 cm row spacing), and P. armeniaca-M. sativa intercropping (JB, 30 cm row spacing) to measure root morphology, soil water content, and aboveground yield from 2020 to 2022. The results showed that P. armeniaca and M. sativa roots exhibited vertical differentiation, with P. armeniaca roots mainly distributing in 40-60 cm soil layer and M. sativa roots concentrating in 20-40 cm soil layer. Such differentiation would facilitate complementary resource utilization. Intercropping decreased root dry weight of P. armeniaca trees by 28.2%-48.7%, but increased specific root length by 9.5%-66.7%. For M. sativa in the near-tree zone, root dry weight decreased by 72.7%-80.6%, while specific root length increased by 44.3%-56.9%. Soil water content in the intercropping system was significantly higher than that in monoculture. Root dry weight of P. armeniaca and M. sativa showed a highly significant negative correlation in JA treatment, but no correlation in JB treatment, indicating that 30 cm row spacing could effectively alleviate root interspecific competition. M. sativa competitiveness gradually increased with coexistence duration, and competitive reversal occurred in JB treatment. Land equivalent ratio exceeded 1.0 in both intercropping treatments, rea-ching 1.31 in JB treatment. The 30 cm row spacing achieved higher system productivity and land use efficiency by reducing M. sativa population density, decreasing root spatial overlap, and alleviating water competition. The 30 cm row spacing was recommended for P. armeniaca-M. sativa intercropping in arid regions. Our findings would provide a scientific basis for the sustainable development of the agroforestry system.