Maize plant density affects yield, growth and source-sink relationship of crops in maize/peanut intercropping

Maize (Zea mays L.)/peanut (Arachishypogaea L.) intercropping has been widely practiced in semi-arid regions to reduce wind erosion and improve resource (e.g. water and light) use efficiencies. Knowledge on optimal maize plant density is lacking from perspective of dry matter accumulation among organs in this intercropping system. We quantified the effect of maize plant density on relative yield total (RYT), maize and peanut yields, and maize dry matter of organs (ears, leaves, and stems) in maize/peanut intercropping. Field experiments were conducted in a semi-arid area of China in 2015 and 2016. Three maize plant densities (6, 9 and 12 plants m(-2)) were tested in maize/peanut intercropping (per unit growing area designed for maize) and sole systems, whereas the plant density of intercropped peanut and sole peanut was fixed as 24 plants m(-2). The beta and logistic growth functions were used to quantitatively characterize the dynamics of dry matter allocation among organs in maize. Increasing maize plant density significantly increased maize yield gain, but not increased peanut yield loss, in maize/peanut intercropping. The greatest yield advantage (RYTs of 1.21 in 2015 and 1.13 in 2016) occured in maize/peanut intercropping with maize planted at 9 plants m(-2). Increasing plant density increased leaf growth rate, but reduced leaf longevity and dry matter allocation to ears for maize grown in both intercropping and sole systems. But, greater increases in leaf growth rate and leaf longevity for intercropped maize compared with sole maize resulted in a greater increase in dry matter accumulation for maize grown at 9 and 12 plants m(-2). Greater increases in ear dry matter accumulation and yield were found for maize grown at 9 plants m(-2) due to greater dry matter allocation to ears. We conclude that the different responses to plant density of the source capacity (leaves) and sink strength (ears) for maize in intercropping and sole systems could help optimize maize plant density (9 plants m(-2)) for greater maize yield gain and yield advantage in maize/peanut intercropping.