Interspecific competition and productivity in a dryland silage maize/alfalfa intercropping system

Cereal-legume intercropping has the potential to reduce the use of nitrogen (N) fertilizer and increase forage yield and quality, however, how to optimize system design to fully realize interspecific complementary and enhance crop production in an annual and perennial crops intercropping was not well understood. This study was conducted to evaluate the interspecific interaction and yield performance of silage maize (Zea mays L.) and alfalfa (Medicago sativa L.) intercropping in response to N management and row arrangement under the rain-fed conditions on the Chinese Loess Plateau. Five planting arrangements, namely, sole maize, sole alfalfa, and maize and alfalfa intercropping in rows of 1:2 (I12), 2:2 (I22), and 2:4 (I24), were compared over a period of 4 years (2018-2021). Two N-levels (150 and 90 kg N ha(-1)) were applied to maize in each planting arrangement. Our results show that maize was the dominant species in 2018. In the next 3 years (2019-2021), maize was outcompeted by alfalfa during the first and second cuts of alfalfa, and complete recovery growth of maize was recorded at the third cut. The interspecific competition of I24 was less severe, resulting in a higher yield than I12 and I22. Although the reduction of N application reduced the biomass and crude protein (CP) yield, it weakened the interspecific competition and substantially increased the land equivalent ratio (LER). I24 under low N yielded more than sole cropping, with the LER based on biomass and CP yield of 1.01-1.12 and 1.08-1.18, respectively. In addition, I24 had the highest net revenue of 24,251 yen ha(-1) on average. Therefore, maize/alfalfa intercrop with a higher alfalfa proportion and a wide strip arrangement (I24) in combination with low N application could alleviate interspecific competition and improve forage production, which is suggested for our study region and similar dryland farming areas worldwide. Maize/alfalfa intercropping provides a basis for grain and livestock mixed farming and helps to improve food supply and resilience of the farming system.