Abstract
The demand to develop fertilizers with higher sulfur use efficiency has intensified over the last decade, since sulfur deficiency in crops has become more widespread. The aim of this study was to investigate whether fertilizers enriched with 2% elemental sulfur (ES) via a binding material of organic nature improve yield when compared to the corresponding conventional ones. Under the scanning electron microscope, the granules of the ES-containing fertilizer were found to be covered by a layer of crystal-like particles, the width of which was found to be up to 60 μm. Such a layer could not be found on the corresponding conventional fertilizer granules. Several fertilization schemes with or without incorporated ES were tested in various durum wheat varieties, cultivated in commercial fields. The P-Olsen content of each commercial field was found to be correlated with the corresponding relative change in the yields (YF/YFBES) with a strong positive relationship. The content of 8 ppm of available soil phosphorus was a turning point. At higher values the incorporation of ES in the fertilization scheme resulted in higher yield, while at lower values it resulted in lower yield, compared with the conventional one. The experimental field trials that established following a randomized block design, were separated in two groups: One with P-Olsen ranging between 18–22 ppm and the other between 12–15 ppm, the results of which corroborated the aforementioned finding. The use of ES in all portions of fertilization schemes provided higher relative yields. The coexistence of ES with sulfate in the granule was more efficient in terms of yield, when compared to the granule enriched with ES alone under the same fertilization scheme and agronomic practice. The application of fertilizer mixtures containing the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT), ES and ammonium sulfate resulted in even higher relative yields. Yield followed a positive linear relationship with the number of heads per square meter. In this correlation, the P-Olsen content separated the results of the two groups of blocks, where the applied linear trend line in each group presented the same slope.
Highlights
Sulfur (S) deficiency in crops has become a common agronomic issue in many countries, mainly due to reduced atmospheric inputs and the use of sulfur free high-analysis fertilizers
The first product of this family of fertilizers was of the 20-10-10 type, where nitrogen was provided as ammonium sulfate, phosphorus as triple superphosphate, while potassium was provided as potassium sulfate
We have found that a portion of the existing microorganisms in the rhizosphere presented arylsulfatase activity [30], releasing sulfate bound in the soil organic matter, the percentage of which increased with the addition of elemental sulfur (ES)-enriched fertilizer
Summary
Sulfur (S) deficiency in crops has become a common agronomic issue in many countries, mainly due to reduced atmospheric inputs and the use of sulfur free high-analysis fertilizers Plants 2019, 8, 2 products that contain a high percentage of nutrients, usually more than 30 per cent). The development of S deficiency in plants during the last decades has been discussed in detail [1,2]. S deficiency in wheat has become increasingly widespread [3]. A detailed discussion of S fertilizers has been provided by Grant and Hawkesford [4]. The granular fertilizers that provide S when applied in crops are mainly based on sulfate salts, because sulfate-S (i.e., S in the form of sulfate) is readily available to plants, highly mobile in the soil profile
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