Benefits of Biochars and NPK Fertilizers for Soil Quality and Growth of Cowpea (Vigna unguiculata L. Walp.) in an Acid Arenosol

Fertilization is required for optimum plant growth, particularly in unfertile soils, while optimizing nutrient use effciency is an alternative to reduce inorganic fertilizer needs and reduce environmental problems caused by nutrient leaching. This study investigated soil properties and cowpea yield responses to biochars(BCs) made from different feedstocks, baby corn peel biochar(BC1), branches of mango tree biochar(BC2), and rice husk biochar(BC3), applied in combination with nitrogen-phosphorus-potassium(NPK) fertilizers.The experiment was conducted in a greenhouse, using an acid sandy soil(Arenosol) that was submitted for 70 d to the following eight treatments: i) control;ii) full dose of NPK(a commercial compound fertilizer(12-24-12 of N-P2O5-K2O)+ urea(46% N));iii) BC1+ half dose of NPK;iv) BC1 + full dose of NPK;v) BC2 + half dose of NPK;vi) BC2 + full dose of NPK;vii) BC3 + half dose of NPK;and viii) BC3 + full dose of NPK. All biochars were applied at a rate of 0.9%(weight/weight), and each type of biochar was combined with half and full doses of NPK fertilizers. Soil pH increased significantly(P < 0.05) in treatments with BC1 and BC2,while cation exchange capacity(CEC) and available P were higher in the treatments with BC1;BC1 and BC2 also induced higher activity of enzymes related to the P cycle and higher cowpea yield. Similar soil properties and cowpea yield parameters were obtained with the full and half doses of NPK fertilizers for each type of biochar used. In conclusion, biochars in the combination with NPK fertilizers improved soil chemistry and enzymatic activities, allowing reduced fertilizer application and food production costs in the acid soil studied.

Increased phosphorus availability to corn resulting from the simultaneous applications of phosphate rock, calcareous rock, and biochar to an acid sandy soil

Phosphorus(P)deficiency is one of the main constraints on crop production in Arenosols(acid sandy soil).The high cost of P fertilizers may represent an insurmountable obstacle in many poor countries,leaving the exploitation of their own calcareous and phosphate rocks as the only low-cost and long-term alternative.Biochar is suggested to have positive effects on soil properties;however,there is no published research on the synergistic effects of biochar and rocky materials in modifying soil properties.The aim of this study was to investigate the chemical and biochemical responses of an acid Arenosol treated with phosphate rock(PR),calcareous rock(CR),and biochar(BC),and the implications for corn yield.A soil from Marracuene District,Mozambique was used,where corn was grown for 90 d with the soil treated with:no addition(control),water-soluble zinc phosphite fertilizer(WSP),PR,WSP+CR,WSP+BC,WSP+CR+BC,PR+BC,and PR+CR+BC.Biochar was produced by pyrolysis of babycorn peels for 4 h at 450?C and applied at 11 g kg-1.The soil pHH2 Oincreased from about 4.54 in the control to 7.38 in the PR+CR+BC treatment.Easily oxidizable organic carbon,cation exchange capacity,and available P were higher in the treatments containing BC than in the control.The treatments containing CR and/or BC led to the highest activities of alkaline phosphomonoesterase,phosphodiesterase,andα-glucosidase,which increased P availability and gave the greatest biomass and yields.We suggest that biochar provides additional soluble P and supplies adsorption sites for phosphate,preventing its evolution to unavailable forms.Thus,PR applied together with BC contributed to an 840%yield increase compared to the control.The treatments containing WSP and BC facilitated phosphite oxidation to phosphate and increased crop yield.