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Subject: Soil Sciences × Author: Barman, Swarnashree × Start date: 2012 ×
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    Impact of biochar and inorganic fertilizer on soil functions and biomass under vegetable production system
    (Punjab Agricultural University, Ludhiana, 2021) Barman, Swarnashree; Mavi, Manpreet S.
    Rice-residue can be pyrolysed to produce biochar which is considered as a better alternative against burning. Conversion of biomass C to the biochar C causes more C retention in soil (about 50%) than the microbial degradation and traditional conservation agriculture. Particularly, if biochar, is returned to the same field where residues would have been removed for pyrolysis, this process may return many nutrients, and improve soil properties. However, biochar’s characteristics and effects on soil fertility have been found to be highly variable, depending on the crop, soil conditions, feedstock, temperature, residence time, rate and method of application. A field experiment was conducted during the year 2018-2019 to study the interactive role of rice-residue biochar and inorganic fertilizer on soil functions under potato-onion cropping system at the research farm of Punjab Agricultural University, Ludhiana, India. Potato (var. Kufri Pukhraj) was sown in the mid-October, 2018 and was harvested manually in the first week of February 2019. Thereafter, onion (var. Punjab Naroya) was sown during mid-February and harvested in 2nd week of June 2019. Before planting potato, experimental plots were amended with different rates of biochar (B0= 0, B0.5= 0.5, B1= 1.0, B2= 2.0 and B4= 4.0 t ha-1) or one level of FYM (50 t ha1 ) in combination with variable rates of inorganic fertilizers (F0= 0, F1= 75%, F2= 100% and F3= 125 per cent of RDF). Urea, single super phosphate, and muriate of potash were used as source of nitrogen, phosphorus and potassium (inorganic fertilizer NPK). Biochar or FYM were mixed in the upper 0-15 cm soil layer only once before sowing of potato and their residual effect was observed during the onion crop. At the harvest, tuber and bulb yield of potato & onion were recorded and nutrient uptake, nutrient use efficiency (NUE) were calculated. Results showed that the plots amended with F3 level of inorganic fertilizer showed maximum tuber and bulb yield and nutrient uptake followed by F2 > F1 > F0 levels. Compared with the unamended control, organic amendments (biochar & FYM) showed positive effect on potato tuber (direct), onion bulb yield (residual) and their corresponding total nutrient uptake respectively. Thus, plots amended with increasing rate of biochar application showed 3-20% and 4-23% more potato tuber and onion bulb yield compared with the unamended control respectively. Similarly, the interactive effect of biochar and inorganic fertilizers at the F2+B2 level showed about 816% and 15-20% higher tuber and bulb yield compared with the plots amended with F2 or F3 level of inorganic fertilizer alone. A comparison between organic amendments (biochar or FYM) showed that the potato tuber yield was observed to be greater (12-30%) in FYM compared with the biochar amended plots, irrespective of the inorganic fertilizer levels. However, total NPK uptake in potato were found maximum in B2 that was at par with FYM amended plots. The residual effect of biochar (B2 or B4 rate) and FYM on onion bulb yield was found to be almost at par. On the other hand, residual effect of biochar on total NPK uptake in onion was found to be greater compared with the FYM amended plots. Furthermore, plots amended with increasing rate of biochar showed 1476% and 6-35% more soil available N and K compared with the unamended control because C:N ratio of biochar decreased over time due to microbial decomposition and increased mineralization of nutrients. Similarly, the interactive effect of biochar and inorganic fertilizers at the F2+B2 level showed about 30-35% and 20-38% higher SAN and SAK compared with plots amended with the F2 or F3 level of inorganic fertilizer alone. In contrast, soil available P was found maximum in FYM compared with the biochar amended plots. As FYM itself contain greater P content, hence it may have released greater content of P in the soil solution. Over time, MBC and DHA also increased with increasing rate of biochar application. Due to slower decomposition, biochar releases small amount of organic carbon (OC) for longer period of time as a source of food for beneficial soil microorganisms. Additionally, application of inorganic fertilizers with organic amendments significantly increased the DHA and MBC compared with the control or inorganic fertilizer alone plots. Similarly, soil mean weight diameter and available water content were also found to be greater in the biochar amended plots because biochar function as a cementing agent to bind micro-aggregates to form macro-aggregates and pore spaces. The beneficial effects of increasing rate of biochar application on soil physico-chemical and biological properties in the study clearly points towards the potential of biochar to be used as a promising organic amendment in the potato-onion system in combination with inorganic fertilizers especially when FYM availability in large quantities is uncertain.