Impacts of chicken manure and peat-derived biochars and inorganic P alone or in combination on phosphorus fractionation and maize growth in an acidic ultisol

The forms of phosphorus(P)in animal manure and peat are different from synthetic P fertilizers and will affect soil P fractions when they are used as P amendments.Effects of chicken manure(CMB)and peat(PB)derived biochars(CMB and PB)alone or in combination with P fertilizer(KH_(2)PO_(4))and rock phosphate(RP)on plant/soil health and soil P fractions in an acidic ultisol were examined with greenhouse pot experiments.The total P rate was constant at 120 mg kg^(−1) in all treatments.Soil P fractions,P uptake,and maize growth were determined after 56 days.Application of CMB combined with P fertilizer or alone significantly increased soil pH,water extractable and relatively labile P,dry matter yield of maize,chlorophyll contents in maize leaves,while decreasing the Fe and Al binding P.Moreover,sole application of CMB and PB showed greater effects than application of P fertilizer alone regarding plant growth and P fractionation.Integration of syn-thetic inorganic P sources with CMB or sole application of CMB is more beneficial than application of inorganic P sources to improve plant growth and P availability.

Effects of long-term phosphorus fertilization and straw incorporation on phosphorus fractions in subtropical paddy soil

Study on soil phosphorus（P） fraction is an important aspect in probing the mechanisms of soil P accumulation in farmland and mitigating its losing risk to the environment. We used a sequential extraction method to evaluate the impacts of long-term fertilization and straw incorporation on inorganic, organic, and residual P（Pi, Po, and Pre） fractions in the plow layer（0–20 cm） of acidic paddy soil in southern China. The experiment comprised of six treatments：（i） no fertilizer control（CK）;（ii） straw incorporation and green manure（SG）;（iii） nitrogen and P fertilizer（NP）;（iv） NP＋SG;（v） NP＋K fertilizer（NPK）; and（vi） NPK＋SG. The results showed that, compared to the initial total soil P content（TSP, 600 mg kg^–1 in 1990）, long-term（20 years） combined continuous P fertilizer and SG significantly increased P accumulation（by 13–20%） while single fertilization（39.3 kg P ha^–1 yr^–1） could maintain soil P status at the most. The average soil P fractions comprised of extractable Pi, Po, and Pre by 51.7, 33.4, and 14.9% in total soil P, respectively. With comparison of no fertilizer addition（CK）, long-term single fertilization significantly（P〈0.05） increased the accumulation of Na HCO3^–, Na OH^–, and HCl^– extractable Pi fractions accounting for two- to three-fold, while SG increased the accumulation of Na HCO3^– and Na OH^– extractable Piand Po accounting for 12–60%. Though the mobilization of Pre fractions was not significant（P〉0.05）, our data indicate that SG may partially substitute for fertilizer P input and minimizing soil P accumulation and subsequent environmental risk in the subtropical paddy soil.