Abstract
The use of rocks containing high amounts of natural zeolites (zeolitites) as soil amendment has been found as a valuable method for increasing agriculture sustainability. However, the potentialities and the effects of zeolitites on the biogeochemical cycles of nitrogen (N) and carbon (C) have still not been clearly addressed in the literature. The objective of this study was therefore to investigate the N and C pools and 15N distribution in an agricultural soil amended with both natural and NH4+-enriched zeolitites with the aim of understanding their effects on the soil-plant system, during sorghum cultivation, under fertilization reductions. Zeolitites were applied to an agricultural soil both at natural state (5 and 15 kg m−2) and in an enriched state with NH4+ ions from pig slurry (7 kg m−2). Both zeolitites at natural and enriched state increased soil cation exchange capacity and affected microbial biomass, causing an initial decrease of microbial C and N and then a possible increase of fungal population. N-NO3− content was lower in natural zeolitite treatments, that lead to a lower NO3− availability for denitrifying bacteria. Zeolitites slightly affected the fixed N-NH4+ pool. δ15N turnover indicated that N from NH4+-enriched zeolitites remained in the soil until the growing season and that fertilizers partially substituted the fixed pool. Leaf δ15N content indicated that plants assimilated N from NH4+-enriched zeolitites and evidenced a higher fertilization recovery in natural zeolitite treatments. Organic C tended to be higher in all zeolitite treatment rhizospheres. In soils amended with zeolitites at natural state (at both application rates) sorghum yield was similar (+3.7%) to that obtained in the control while it was higher (+13.9%) in the plot amended with NH4+-enriched zeolitites.
Highlights
The intensification of agricultural and zootechnical technology has brought food production to a high cost in terms of environmental quality [1,2,3,4]
We present a detailed study on the dynamics, of both organic and inorganic N and C pools in soils amended with natural zeolitites (NZ) and NH4 + -enriched zeolitite (NEZ)
A detailed investigation of the N-C pools and δ15N dynamics in the soil-sorghum system were studied in a field amended with natural and NH4+-enriched zeolitites, under fertilization reductions
Summary
The intensification of agricultural and zootechnical technology has brought food production to a high cost in terms of environmental quality [1,2,3,4]. Zeolitites are rocks containing more than 50% of zeolites [6], hydrated minerals capable of binding NH4 + from solutions in their extra-framework sites, preventing NH4 + leaching by rainfalls and/or irrigation In this way, zeolitites can increase nitrogen use efficiency (NUE) and behave as slow-releasing fertilizers, resulting in a more sustainable agriculture, where the amount of fertilizers can be decreased without lowering the production yield [6,7,8,9,10,11,12]. The aforementioned studies provide very important and useful information regarding the beneficial effects obtained using NZ in terms of crop yield, environmental protection (reduction of nitrate leaching) and water use efficiency Notwithstanding these promising results, a detailed study on the N and C pools dynamics in a zeolitite-amended field is still lacking
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