Soybean (Glycine max (L.) Merrill) intercropping with reduced nitrogen input influences rhizosphere phosphorus dynamics and phosphorus acquisition of sugarcane (Saccharum officinarum)
2020
Tian, Jihui | Tang, Mengtian | Xu, Xia | Luo, Shasha | Condron, Leo M. | Lambers, H. | Cai, Kunzheng | Wang, Jianwu
Reducing nitrogen (N) input can improve crop productivity in cereal-legume intercrops, but the impact on phosphorus (P) acquisition is unclear. A 10-year (2009–2018) field experiment was conducted to quantify how P acquisition by sugarcane (Saccharum officinarum) was affected by intercropping with soybean (Glycine max (L.) Merrill at 1:1 and 1:2) with two N inputs (300 kg ha⁻¹ [reduced], 525 kg ha⁻¹ [conventional]). Nitrogen was supplied only to the sugarcane crop, and soybean received no N. There was a significantly higher land-equivalent ratio of sugarcane-soybean intercropping than of the sole cropping, and the intercropping advantage was more pronounced under reduced N input which can be associated with high degree of complementary N use. Furthermore, soybean intercropping with reduced N input stimulated acid phosphomonoesterase activity and depleted organic P in the rhizosphere of sugarcane, resulting in increased sugarcane stem P concentration and system P-use efficiency. The interspecific facilitation of P acquisition could be associated with the increased symbiotic N₂ fixation in soybean, soil microbial biomass and activity under reduced N input. In conclusion, soybean intercropping with reduced N input to sugarcane enhanced rhizosphere enzymatic organic P transformation and sugarcane P acquisition, which may contribute to maintaining a sustainable sugarcane production under low N supply. The findings advance our understanding of interactions between N and P cycling and provide new evidence for the value of cereal-legume intercrops in reducing fertilizer input.
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