RESUMO
Application of organic residues such as farm manure and biochar in various agricultural environments have shown positive effects on soil carbon sequestration. However, there is a lack of consensus regarding the agronomical benefits of a single and small dose of biochar and farm manure in arid alkaline soils. Therefore, a field experiment with the given treatments (1) control (no amendment), (2) acidified manure (AM) at 300 kg ha-1, (3) nitrogen (N) enriched biochar (NeB) at 3 Mg ha-1, and (4) an equal combination of AM + NeB (150 kg ha-1 AM + 1.5 Mg ha-1 NeB)) was conducted in a typical cotton-wheat cropping system. A parallel laboratory incubation study with the same amendments was carried out to account for soil carbon dioxide emission (CO2). The N enrichment of biochar and its co-application with acidified manure increased soil mineral N (NO3- and NH4+) in the topsoil (0-15 cm), and increased total N uptake (25.92% to 69.91%) in cotton over control, thus reducing N losses and increased uptake over control. Compared to the control, co-application of AM + NeB significantly improved soil N and P bioavailability, leading to increased plant biomass N, P, and K (32%, 40%, 6%, respectively) uptake over control. The plant's physiological and growth improvements [chlorophyll (+ 28.2%), height (+ 47%), leaf area (+ 17%), number of bolls (+ 7%), and average boll weight (+ 8%)] increased the agronomic yield in the first-season crop cotton by 25%. However, no positive response was observed in the second season wheat crop. This field study improved our understanding that co-application of acidified manure and N-enriched biochar in small dose can be a strategy to achieve short-term agronomic benefits and carbon sequestration in the long run.
