Farm yard manure enhances phosphate fertilizer use efficiency in different upland rice genotypes through mitigating aluminium toxicity

Abstract

23Upland rice production on weathered soils is often constrained by phosphorus (P) deficiency and soil 24 acidity. Farmyard manure application (FYM) can sharply enhance yields and agronomic P fertilizer (TSP) 25 efficiency. We tested the hypothesis that rice genotypes differ in the extent of using organic P and offering 26 distinct benefits under TSP-FYM combinations. Multiple field trials were conducted in the uplands of 27 Madagascar, with factorial combinations of six genotypes, FYM, and TSP applications, with blanket N&K 28 additions. Rice grain yields reached 6 t ha -1 after three years of TSP+FYM application, were lower when 29 FYM or TSP were used separately, while crops failed under zero P input. Genotypic differences were 30 inferior to the large treatment effects. Application of FYM increased soil pH and CaCl2-extractable P while 31 decreasing CaCl2-extractable aluminium. An additional liming trial indicated that beneficial effects of FYM 32 over TSP relate to liming effects. Genotypic ranking of yields and agronomic efficiency was inconsistent, 33 without superior genotypes under FYM versus TSP. However, Chomrong Dhan and FOFIFA 172 showed 34 superior yields under TSP+FYM. The FYM application lowers aluminium toxicity which overrules potential 35 effects of organic P supply. Aluminium tolerance should be included when developing rice genotypes for 36 low P tolerance in weathered soils.NA Data not available. a Phosphorus Acquisition Efficiency, expressed as total P uptake in mg at low P availability in the soil. b Root Efficiency, expressed as total P uptake per unit root size (either root biomass in g or root surface area in cm 2 ).