Effects of organic matter addition on phosphorus availability to flooded and nonflooded rice in a P‐deficient tropical soil: a greenhouse study

Abstract

Addition of organic matter (OM) to flooded soils stimulates reductive dissolution of Fe(III) minerals, thereby mobilizing associated phosphate (P). Hence, OM management has the potential to overcome P deficiency. This study assessed if OM applications increases soil or mineral fertilizer P availability to rice under anaerobic (flooded) condition and if that effect is different relative to that in aerobic (nonflooded) soils. Rice was grown in P-deficient soil treated with combinations of addition of mineral P (0, 26 mg P/kg), OM (0,~9 g OM/kg as rice straw + cattle manure) and water treatments (flooded vs nonflooded) in a factorial pot experiment. The OM was either freshly added just before flooding or incubated moist in soil for 6 months prior to flooding; blanket N and K was added in all treatments. Fresh addition of OM promoted reductive dissolution of Fe(III) minerals in flooded soils, whereas no such effect was found when OM had been incubated for 6 months before flooding. Yield and shoot P uptake largely increased with mineral P addition in all soils, whereas OM addition increased yield and P uptake only in flooded soils following fresh OM addition. The combination of mineral P and OM gave the largest yield and P uptake. Addition of OM just prior to soil flooding increased P uptake but was insufficient to overcome P deficiency in the absence of mineral P. Larger applications of OM are unlikely to be more successful in flooded soils due to side effects, such as Fe toxicity.

Effects of soil flooding and organic matter addition on plant accessible phosphorus in a tropical paddy soil: an isotope dilution study

“…The E AEM ‐values measured in the first experiment confirmed the better mobility of P under flooded condition unlike the L ‐values. However, the additional release of P due to flooding is relatively small (< 8 mg P kg −1 ) and is unlikely sufficient to increase the P‐availability when contrasting with the effects of inorganic P fertilizer addition as discussed before ( Rakotoson et al, 2015). The generally observed increase of P availability upon flooding (see introduction) is, therefore, unlikely due to ‘unlocking' P from non‐isotopically exchangeable P from soil.…”

“…However, that increase of labile P due to OM addition was argued to be too low to overcome P deficiency. Pot trials indeed confirmed that addition of fresh OM can increase P availability for rice, but this was not sufficient to overcome P deficiency without inorganic P fertilization ( Rakotoson et al, 2015).…”

Changes in soil aggregate‐associated enzyme activities and nutrients under long‐term chemical fertilizer applications in a phosphorus‐limited paddy soil

“…Fertilizer amendment is a key factor to increase crop production. Application of nitrogen (N), phosphorus (P) and potassium (K) in the form of chemical fertilizers increases the availability of nutrients to crops and may also influence soil quality by changing its physical and chemical properties and the bioprocesses that occur within soil (Rakotoson et al ., ). These changes are susceptible to the type of fertilizers, crop regimes and soil fertility conditions (Zhong & Cai, ; Jiang et al ., ; Su et al ., ).…”

Speciation and sorption of phosphorus in agricultural soil profiles of redoximorphic character

“…In this case, microbial respiration leads to reductive dissolution of Mn(III, IV) and Fe(III) (hydr)oxides, which enhances P availability in the soil solution by the release of P adsorbed to minerals (Lovley 1991 ; Peretyazhko and Sposito 2005 ; Maranguit et al 2017 ). This mechanism of phosphate mobilization has been successfully employed by flooding of soils to increase the P availability and thus the P nutritional status of, e.g., rice plants (Islam and Islam 1973 ; Seng et al 1999 ; Rakotoson et al 2015 ). However, enhanced P mobilization may also be of disadvantage since increased P solubility can lead to P leaching and nutrient loss with its unfavorable consequences not only for crop plants but also for aquatic ecosystems (Sims et al 1998 ; Nausch et al 2017 ).…”