Impact of biochar and inorganic-P fertilizer on soil phosphorus dynamics and crop
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Date
2022
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Punjab Agricultural University, Ludhiana
Abstract
Owing to its fixation in soil, phosphorus is one of the most limiting nutrients for crop productivity. Therefore, continued inputs of P to soil are necessary to sustain crop productivity. However, the non-renewable nature and cost associated with mineral P fertilizers necessitate the need to find alternate sources for sustainable P management. In this context, biochar produced upon thermochemical decomposition of biomass can serve as a viable P source. However, a clear understanding of the mechanisms affecting P availability with different biochar types and rates either applied alone or in combination with inorganic-P fertilizer levels remains elusive. Therefore, a pot and incubation study were conducted to study the impact of different biochar types and rates with or without inorganic-P fertilizer levels on crop biomass and phosphorous availability in soil with varying P status. For the pot study, low and high P status soil was amended with four rates of the maize stover biochar (0, 2, 4, and 8 t ha-1) and three levels of the inorganic-P (KH2PO4) (0, 30, and 60 mg kg-1) with wheat as a test crop. Increasing rates of biochar and inorganic-P led to a significant increase in P availability (Olsen-P, microbial biomass P, and P fractions) and crop biomass. Besides, grain yield achieved with application of 2 t ha-1 biochar alone was comparable to inorganic-P alone both with 30 and 60 mg kg-1 treatment in low and high P status soil. However, the changes in P dynamics with biochar application were more apparent in low P than the high P status soil. Furthermore, biochar (at the rate of 1%) derived from different feedstocks like maize stover (MSB), palm wood (PWB), and poultry manure (PMB) were applied in combination with two rates of inorganic-P (KH2PO4) (0 and 60 mg kg-1) to low and high P status soil for the incubation experiment. In general, a maximum increase in Olsen-P and soil P fractions was observed with PMB followed by MSB > PWB > inorganic-P. Thus, the results of the study indicated that biochar application improved the soil P availability either directly due to the release of P from biochar itself or indirectly through the decrease in P sorption of the amended soil or improved microbial biomass. Besides, an increase in organic-P and lower alkaline phosphomonoesterase activity upon biochar application indicated a slow P turnover rate in the soil. However, the increment observed in grain yield and soil P availability upon biochar application was better when applied alone rather than its co-application with the inorganic-P. Therefore, it may be concluded that biochar can serve as a suitable substitute for mineral P fertilizers for fulfilling crop P demand. However, future studies must carefully validate the potential of biochar derived from different feedstock and rates of application through long-term field trials before recommending its extensive use as a source of P in agriculture.
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Jagmandeep Kaur (2022). Impact of biochar and inorganic-P fertilizer on soil phosphorus dynamics and crop (Unpublished M.Sc. thesis). Punjab Agricultural University, Ludhiana, Punjab, India.