Ammonium sulfate enhances the effectiveness of reactive natural phosphate for fertilizing tropical grasses

Carlos E.A Cabral,Edna M Bonfim-Silva,Carla H.A Cabral,Kassio S Carvalho,Ana P Bays,Jenifer S Mattos,Letícia B Alves,Alyce R.M Santos

doi:10.17138/tgft(8)86-92

Carlos E.A Cabral, Edna M Bonfim-Silva + Show 6 more

Open Access

https://doi.org/10.17138/tgft(8)86-92

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Abstract

Reactive natural phosphate is a slow and gradual solubilizing fertilizer, which makes it difficult to use in neutral to alkaline soils. Nitrogen fertilizers which acidify the soil may increase the possibility of using this phosphate fertilizer commercially. Two greenhouse experiments were conducted to compare responses of Xaraés palisadegrass (Urochloa brizantha syn. Brachiaria brizantha cv. Xaraés) and Mombasa guineagrass (Megathyrsus maximus syn. Panicum maximum cv. Mombasa), when different combinations of P and N fertilizers were applied during the establishment phase in non-acidic soils or with corrected acidity. The experiments were carried out in a completely randomized design with 3 fertilizer combinations (simple superphosphate plus urea, SSU; natural reactive phosphate plus urea, RPU; and natural reactive phosphate plus ammonium sulfate, RPAS). There was no difference in tiller density, leaf numbers, forage mass, leaf mass and stem mass for either forage on SSU and RPAS treatments but they exceeded those on RPU. Soil pH was lower in soil fertilized with ammonium sulfate than in soil fertilized with urea. Applying natural reactive phosphate plus ammonium sulfate seems as effective as simple superphosphate plus urea in promoting increased growth in tropical grasses on low-P soils. Longer-term and more extensive field studies are needed to determine if these results can be reproduced in the long term, and the level of soil acidification over time.

Highlights

Phosphorus plays an important role in development of root systems of plants, and concentration of this nutrient in tropical soils is often low (Marcante et al 2016; Zambrosi et al 2017)
Reactive natural phosphates come from sedimentary rocks and differ from those from igneous and metamorphic rocks, which have low reactivity and are commonly called ‘rock’ phosphate (Corrêa et al 2005)
The lower cost of reactive natural phosphate results from physical processing being all that is involved in manufacture, as opposed to water-soluble fertilizers, which are both milled and chemically (Ivanova et al 2006) or thermally solubilized

Summary

Introduction

Phosphorus plays an important role in development of root systems of plants, and concentration of this nutrient in tropical soils is often low (Marcante et al 2016; Zambrosi et al 2017). While water-soluble phosphate fertilizers, such as triple and single superphosphate, are most commonly used, a lower-cost alternative is reactive natural phosphate. Reactive natural phosphates come from sedimentary rocks and differ from those from igneous and metamorphic rocks, which have low reactivity and are commonly called ‘rock’ phosphate (Corrêa et al 2005). The lower cost of reactive natural phosphate results from physical processing being all that is involved in manufacture, as opposed to water-soluble fertilizers, which are both milled and chemically (Ivanova et al 2006) or thermally solubilized

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