Effect of soil P status on barley growth, P uptake, and soil microbial properties after incorporation of cover crop shoot and root residues

Background Cover crops (CC) introduced to reduce leaching of nitrate may also improve soil microbial properties and phosphorus (P) uptake in crops that follow. These effects may depend on soil P status and the quality of the CC residues. Aim Our aim was to quantify the more persistent effects of incorporation of residues of three different CC species on barley growth and P uptake and whether any response in growth and P uptake was related to soil P status and changes in soil microbial properties. Methods We examined the impact of soil P status, CC species, and residue fraction (shoots and/or roots) on the growth of winter barley (Hordeum vulgare) and soil microbial properties. Shoot and root residues from three contrasting CC (oats, Avena sativa; corncockle, Agrostemma githago; lupine, Lupinus angustifolius) were incubated for 2 months in soil with low and medium P status. Dry matter yield and P offtake characterized effects of CC residues on barley while phospholipid fatty acids (PLFAs), neutral lipid fatty acids (NLFAs), and enzyme activity characterized soil microbial properties after barley harvest. Results Effects of shoot residues on barley yield and P offtake appeared neutral or positive and not affected by soil P status, while the effect of root residues appeared negative for medium P soil and neutral for low P soil. With lupine shoot biomass, however, barley yield and P offtake increased in both soils. Neither CC treatments nor soil P status affected the microbial community composition (bacterial and fungal specific PLFAs). Lupine roots increased phosphomonoesterase, and lupine residues generally stimulated microbial abundance (total microbial PLFAs) compared to other CC treatments. Conclusion We conclude that the effect of CC residues on the following crop and soil microorganisms depends on soil P status and that lupine had the largest positive impact on barley growth.