Effects of Poplar-crop Intercropping and Fertilization on the Soil Nutrients and Plant Growth

This study aimed to clarify the effects of poplar-crop intercropping and fertilizer application on soil nutrients and plant growth.

A pot experiment was conducted to investigate soil nutrients and plant growth under three planting patterns: poplar (Populus deltoides) monoculture, wheat (Triticum aestivum)/soybean (Glycine max) monoculture, and poplar-wheat/soybean intercropping. Each planting pattern was subjected to three fertilizer application rates (10, 5, and 0 g of compound fertilizer per pot).

Fertilizer application reduced soil pH by 0.1–0.4 units. Under the same planting pattern, the concentrations of soil nitrate nitrogen (NO₃⁻-N), available phosphorus (AP), and available potassium (AK) increased with increasing fertilizer application rate. In addition, at the same fertilizer application rate, soil AP and AK concentrations in the poplar monoculture and poplar-crop intercropping systems were more than 80% and 20% higher, respectively, than those in the wheat/soybean monoculture systems. In both monoculture and intercropping systems, crop yield and poplar growth were highest under the 10 g·pot⁻¹ fertilization treatment, followed by the 5 g·pot⁻¹ fertilization treatment, and lowest under the no-fertilization treatment. At the same fertilizer application rate, crop yield and poplar growth in the poplar-crop intercropping system were approximately 50% and 10% lower, respectively, than those in the corresponding crop and poplar monoculture systems. However, the land equivalent ratio of the poplar-crop intercropping system was greater than 1, indicating higher overall productivity than either poplar or crop monoculture.

Poplar planting promoted soil phosphorus activation and potassium release, thereby increasing soil AP and AK concentrations. Fertilizer application enhanced crop yield and poplar growth. The fertilizer requirement of the poplar-crop intercropping pattern was greater than that of either poplar or crop monoculture. Overall, poplar-crop intercropping was conducive to improving integrated land productivity.