Field Crops Research 198 (2016) 61–69 Contents lists available at ScienceDirect Field Crops Research jou rn al hom epage: www.elsevier.com/locate/fcr Farmyard manure application has little effect on yield or phosphorus supply to irrigated rice growing on highly weathered soils A. Andriamananjara a,∗,1 , T. Rakotoson a,b,1 , O.R. Razanakoto a , M.-P. Razafimanantsoa a , L. Rabeharisoa a , E. Smolders b a Laboratoire des Radiosotopes, Université d’Antananarivo, Route d’Andraisoro B.P. 3383, Antananarivo 101, Madagascar b Department Earth and Environmental Sciences, Laboratory of Soil and Water Management, K.U. Leuven, Kasteelpark Arenberg 20, 3001 Heverlee, Belgium a r t i c l e i n f o Article history: Received 15 February 2016 Received in revised form 23 August 2016 Accepted 24 August 2016 Keywords: Phosphate Deficiency Rice Manure Bioavailability Fertilizers System for rice intensification a b s t r a c t It is well established that organic matter application can enhance soil phosphorus (P) bioavailability in acid, weathered soils. It is yet unclear to what extents this also holds for irrigated rice in flooded soils where, in principle, organic matter may unlock soil P due to reductive dissolution of Fe-(III) minerals. This study was set up to identify if farmyard manure (FYM) can enhance the use efficiency of soil-P and mineral fertilizer-P in irrigated rice after excluding N and K effects. Field trials with factorial supplies of FYM and banded mineral P fertilizer (Triple Superphosphate or TSP) were set up at three irrigated rice fields in Madagascar with equal annual applications during three consecutive years. All treatments received a blanket N and K application. The FYM rates were within local agronomic rates and TSP rates were maximally 80 kg P ha −1 . Total P application from FYM and TSP increased rice grain yields of 4.2 Mg ha −1 at the +NK-control to, on average for all years and fields, 5.5 Mg ha −1 at highest P doses. Grain yield generally responded to TSP but not to FYM. Total P uptake in grain and straw increased with total P application. Positive effects of FYM on P uptake were mainly related to its P application to irrigated rice soils. The soil P balances amended with FYM only, i.e. the common local farmers practice, were negative. At adequate N and K supply, effect of FYM application on increasing soil or fertilizer P use efficiency was not detectable in irrigated rice; it mainly recycles P. © 2016 Elsevier B.V. All rights reserved. 1. Introduction Phosphate deficiency is ubiquitous in the highly weathered acid soils in Sub-Saharan Africa due to the strong immobilization of PO 4 anions on the Fe and Al oxyhydroxides. The P use efficiency of added mineral fertilizers is very small and its residual value low. Different agricultural systems have been developed to improve the availability of soil- and fertilizer P. Rotations of grain crops with leguminous plants improve P-supply to the subsequent crop and increased organic matter (OM) applications to soil, either alone or in combination with mineral P can increase P availability (Ayaga et al., 2006; Nziguheba et al., 2000; Vanlauwe et al., 2000). The effects of OM application on increased soil P availability is indicated by higher soil P extractability, higher yield or higher crop P uptake in treatments with mixtures of OM-derived P and mineral P com- pared to mineral P only at equivalent total P application (Nziguheba ∗ Corresponding author E-mail addresses: njaraandry1@gmail.com, njaraandry@yahoo.fr (A. Andriamananjara). 1 These authors contributed equally. et al., 2002, 2000). The increase of P availability due to OM addition can be related to various mechanisms: (i) organic anions released during its decomposition compete with P on soil binding sites; (ii) OM can locally increase the soil pH, thereby reducing the soil PO 4 binding (Haynes and Mokolobate, 2001; Hue, 1991); (iii) enhanced biological cycling of P in soil (Ayaga et al., 2006) and (iv) any other indirect physical or nutritional effect from OM applied to soils on plants that affects their P uptake potential, even after correcting (as well as possible) for other nutrients besides P in the OM. The OM-P interactions are well studied in aerobic soils. Less is known if OM supply can also enhance P supply at P deficient condi- tions in waterlogged (flooded) soils where soil chemical conditions differ from aerobic soils. Upon flooding soils, anaerobic reactions release some PO 4 due to reductive dissolution of Fe(III) oxides, due to competitive adsorption of dissolved organic matter (DOM), and due to formation of aqueous ternary DOM-Fe-PO 4 or DOM- Al-PO 4 complexes (Kirk, 2004; Kirk et al., 1990; Peretyazhko and Sposito, 2005; Ponnamperuma, 1985). These reactions explain why, in general, irrigated (flooded) rice exhibits less P-deficiency than rainfed (upland) rice grown in corresponding soils (Huguenin-Elie et al., 2009; Rabeharisoa et al., 2012). In addition, waterlogging soils strongly increases the effective diffusion of P in soil due to mere http://dx.doi.org/10.1016/j.fcr.2016.08.029 0378-4290/© 2016 Elsevier B.V. All rights reserved.