Linking maize root size to phosphorus acquisition and productivity in diversified cropping systems

Intercropping and mixed-cropping of plant varieties can increase yields; however, the impacts of root size and morphology on nutrient uptake and plant growth in these systems remain unclear.

Two maize varieties with small root system (Shengrui 99, M1) and large root system (Zhongke 11, M2) were intercropped with soybean (D76-1609), and also grown under mixed-cropping conditions, with two phosphorus (P) levels (low P: 2.97 mg P kg^-1 soil, LP, and high P: 175 mg P kg^-1 soil, HP) under controlled environment.

Results showed that both intercropping and mixed-cropping conferred advantages over monoculture, with land equivalent ratios (LER) ranged from 1.87 to 2.53. The advantage of intercropping was greater under LP conditions, average 8.65% higher, while mixed-cropping performed better under HP conditions, increased by 26.20%. Nutrient absorption equivalent ratios were also greater than 1 in inter- and mixed-cropping systems. Intercropping with soybean enhanced maize root length under LP, with M2 showing a more pronounced response. Specific nutrient uptake per unit root length and nitrogen (N) and P competition ratios were significantly influenced by P supply and planting pattern (P<0.05). Notably, under LP conditions, M2 exhibited stronger competitive ability for P, while M1 showed greater N competitiveness.

These results suggest that genetic improvement of maize root size could enhance plant growth and improve resource competitiveness in intercropping and mixed-cropping systems. Furthermore, depending on P availability, larger root systems in maize could increase overall productivity in intercropping and mixed-cropping systems.