Abstract
Phosphorus (P) is the second most important mineral nutrient for plant growth and plays a vital role in maintaining global food security. The natural phosphorus reserves [phosphate rock (PR)] are declining at an unprecedented rate, which will threaten the sustainable food supply in near future. Rendered animal byproducts such as meat and bone meal (MBM), could serve as a sustainable alternative to meet crop phosphorus demand. Even though nitrogen (N) from MBM is readily mineralized within a few days, >75% of the P in MBM is present as calcium phosphate that is sparingly available to plants. Thus, application of MBM with the aim of meeting crop N demand could result in buildup of P reserves in soil, which necessitates the need to improve the P mobilization from MBM to achieve higher plant P use efficiency. Here, we tested the potential of two microbial inoculum-arbuscular mycorrhizal fungi (AMF) and P solubilizing fungi (Penicillium bilaiae), in improving the mobilization of P from MBM and the subsequent P uptake by maize (Zea mays). Compared to the non-inoculated MBM control, the application of P. bilaiae increased the P mobilization from MBM by more than two-fold and decreased the content of calcium bound P in the soil by 26%. However, despite this mobilization, P. bilaiae did not increase the tissue content of P in maize. On the other hand, AMF inoculation with MBM increased the plant root, shoot biomass, and plant P uptake as compared to non-inoculated control, but did not decrease the calcium bound P fraction of the soil, indicating there was limited P mobilization. The simultaneous application of both AMF and P. bilaiae in association with MBM resulted in the highest tissue P uptake of maize with a concomitant decrease in the calcium bound P in the soil, indicating the complementary functional traits of AMF and P. bilaiae in plant P nutrition from MBM. Arbuscular mycorrhizal fungi inoculation with MBM also increased the plant photosynthesis rate (27%) and root phosphomonoesterase activity (40%), which signifies the AMF associated regulation of plant physiology. Collectively, our results demonstrate that P mobilization and uptake efficiency from MBM could be improved with the combined use of arbuscular mycorrhizal fungi and P. bilaiae.
Highlights
Phosphorus (P) is a key nutrient for plant growth and its continued supply is critical for achieving global food security
15% of the P was present as organic P in meat and bone meal (MBM) (Figure 1)
Even though the exact mechanism of P mobilization by P. bilaiae in our study is not evident, based on the previous studies [8, 32, 39, 40], bilaiae to facilitate this process. This is partly evident from we propose that H+ and organic acids released by the P. the lower soil solution pH in MBM + P. bilaiae treatments
Summary
Phosphorus (P) is a key nutrient for plant growth and its continued supply is critical for achieving global food security. The current global reserves of PR (16,000 MT), at the present consumption rate (160 MT year−1), are expected to deplete within the 100 years [3, 4], which threatens sustainable food production. Low P use efficiency of crops (20–25%) exacerbates this problem, requiring constant addition of P fertilizers to meet their P demand. Available MBM is nutrient-rich and contains up to 8% nitrogen (N) and 5–10% P, and can be used as a potential N and P fertilizer [7]. More than 75% of P in MBM is calcium-bound P (as hydroxyapatite) with low bioavailability for plants [7]. There is an urgent need to improve the mobilization and plant uptake of P from MBM for its sustainable, efficient, and economical use as an organic fertilizer
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