Availability of fertiliser sulphate and elemental sulphur to canola in two consecutive crops

Abstract

Aims We compared elemental sulphur (ES) and sulphate fertilisers in terms of yield and S uptake. Methods Two consecutive canola crops were grown on 35 S-labelled soil amended with ammonium sulphate, ES-bentonite pastilles (90 % ES), or S-fortified ammonium phosphate (NP) fertilisers containing both sulphate-S and ES (5-8 % ES). The shoot yield, S concentration and specific activity of S in the shoot were determined. Results In the first crop, the yield was significantly lower in the control (without added ES) and ES pastille treatments than in the other treatments. Sulphur uptake was highly correlated with the added sulphate rate. In the second crop, the yield and S uptake was highest for the S-fortified NP fertilizers. The contribution of ES to the S uptake was circa 20 % in the first crop and 43 % in the second crop for the S-fortified NP fertilisers, but was negligible for the ES pastilles. Modelling indicated an oxidation rate of 0.6−0.7 % per day for the S-fortified NP fertilisers and 0.03 % per day for the ES pastilles. Conclusions The contribution of ES pastilles to S uptake was negligible in both crops. In contrast, Sfortified NP fertilisers showed a significant contribution of ES and higher S availability than sulphate-only fertiliser in the second crop.

Oxidation of Elemental Sulfur in Granular Fertilizers Depends on the Soil-Exposed Surface Area

“…The estimated oxidation rate was around 0.005 d −1 , which is in good agreement with the value estimated from a pot trial with MES fertilizer (0.007 d −1 ; Degryse et al, 2016). Based on the oxidation rates found in this study and given the temperature dependence of ES oxidation, around 40% is expected to be oxidized during 1 yr at mid-temperate latitudes assuming that the soil has a similar oxidation capacity as the ones used in this study.…”

“…They also found that, while micronized ES was as effective as SO 4 -S fertilizer, responses to the ES-bentonite fertilizer were minimal in the first year and still limited in the second year (average oxidation estimated to be 14%) despite thorough mixing of the soil before the second-year experiment. In a recent pot trial study using inverse isotope dilution, we found negligible contribution of ES pastilles to S uptake by canola in two consecutive crops (Degryse et al, 2016). Some other studies found better performance of ES-bentonite products in the second or subsequent years after initial application Solberg et al, 2007).…”

Agronomic Effectiveness of Granular Nitrogen/Phosphorus Fertilizers Containing Elemental Sulfur with and without Ammonium Sulfate: A Review

“…Another example showing the importance of using multiple S rates to compare various S sources is demonstrated in a recently published study by Degryse et al (2016) for two successive canola crops (6 wk each) on comparing AS with two MAP-(ES+AS) products as shown in Table 3. Both MAP-(AS+ES) products were statistically as effective as AS in dry matter yield based on a single rate at 20 mg total S kg -1 for the first canola crop.…”

“…Table 3. Dry matter yield (DMY) and S uptake by two successive canola crops (6 wk each) obtained with ammonium sulfate (AS) and two granular monoammonium phosphate (MAP)-(AS+ elemental sulfur [ES]) products (Degryse et al, 2016). and resulted in enhancing S uptake by the second crop.…”

“…In a study similar to the procedure used by Degryse et al (2016), Kroeker (2005) conducted a growth chamber study to compare a homogenous granular NPS (15%S) fertilizer containing (7.5% ES + 7.5% AS-S) and MAP+ES (particle size of ES < 150 µm) with MAP+AS for two successive canola crops (45 d each) in two soils that were treated with 41 mg S pot -1 (Table 4). The apparent sum of S recovery by the two canola crops from the NPS fertilizer was approximately 50% of that from MAP+AS, whereas MAP+ES was ineffective in increasing S uptake as compared with MAP (no S) ( Table 4).…”