Retention and release of nutrients from polyhalite to soil

Recent discoveries of polyhalite (K₂SO₄.MgSO₄.2CaSO₄.2H₂O) in the UK provide an alternative to conventional fertilizer sources. This work investigated the interaction of polyhalite, commercially known as POLY4, with soil using leaching columns. Different physical forms of polyhalite (powder, crushed rock and granules) were compared to potassium chloride (KCl) for the movement of potassium, calcium, magnesium and sulphur (as sulphate) through the soil profile using 19.7 L of water, equivalent to 4,500 mm rainfall. The nutrients from polyhalite were found to be available at 30 cm depth, with calcium showing signs of interacting with the soil clay particles to release cationic nutrients. Polyhalite granules showed the greatest release of sulphate, magnesium and calcium as a proportion of the additional nutrient with 127%, 71% and 102%, respectively leached. For potassium, all forms of polyhalite had greater release than KCl (powder = 58%; granules = 86%; crushed rock = 57% and KCl 16%). Nutrients from polyhalite and those mobilized from soil interactions are present in soil solution indicating availability for plant growth.     

Ammonia volatilization from ammonium sulfate as sulfur source

Surface application of ammonium sulfate (AMS) as S source to soils with pH ≥7.0 is subjected to ammonia (NH₃) volatilization. However, AMS volatilizes less NH₃ than urea does. In soils with pH <7.0, unlike urea, very little NH₃ volatilization from AMS occurs. The associated N with AMS may enhance early biological N fixation by leguminous crops as compared to S sources without N such as polyhalite.     

Response of tomato to polyhalite as a multi-nutrient fertilizer in southeast Brazil

Abstract

Limited information on the agronomic performance of polyhalite (K₂SO₄.MgSO₄.2CaSO₄.2H₂O) motivated us to establish two field trials in Sao Paulo, Brazil. The objective was to evaluate the comparative responses of tomato to muriate of potash (MOP), sulfate of potash, potassium magnesium sulfate, and polyhalite at different graded doses of potassium (K) application supplying varied amount of secondary nutrients. Under very low soil K conditions, polyhalite resulted in significantly higher marketable fruit yield, and higher foliar and fruit K and sulfur (S) concentrations than other K sources. This was not the case under medium soil K levels, that is, 101?mg?kg^?1. Likewise, polyhalite enhanced postharvest residual soil calcium (Ca), magnesium (Mg), and S than other evaluated sources. Depending on soil nutrient status and the cost of polyhalite, tomato farmers of Brazil could consider polyhalite as an option to meet crop K and secondary nutrient requirements.     

杂卤石对花生生长及养分吸收的影响

为探讨杂卤石在北方典型棕壤上的应用效果,以花生为研究对象,于2015年2月至6月通过盆栽试验,以不施钾肥为对照,研究了杂卤石不同用量对花生荚果质量和花生秧干质量的影响,并比较了其与氯化钾、硫酸钾镁和硫酸钾对花生养分吸收及产量的影响差异。结果表明：在每千克土施用0~0.133 g K₂O时,随着杂卤石施用量增加,花生荚果质量和花生秧干质量呈现出先增高后降低的趋势,其中每千克土施用0.089 g K₂O时均最大,花生荚果质量较其他处理提高14.74%~48.08%,与每千克土壤施入0、0.022 g和0.044 g K₂O的处理差异达显著水平;花生秧干质量较其他处理显著提高13.33%~49.08%。在每千克土施用0.089 gK₂O的条件下,杂卤石处理花生荚果质量较氯化钾、硫酸钾镁和硫酸钾处理提高2.42%~12.32%,与氯化钾处理差异达显著水平,花生秧干质量较三种常规钾肥处理显著提高18.49%~25.44%。杂卤石处理植株氮含量较氯化钾、硫酸钾镁和硫酸钾处理平均显著提高1.92%~6.78%,植株钾含量较氯化钾、硫酸钾镁处理平均显著提高15.37%,钾肥表观利用率显著高于氯化钾和硫酸钾镁处理,钾肥农学利用率及钾肥偏生产力显著高于氯化钾处理,植株钙含量较氯化钾、硫酸钾镁和硫酸钾处理平均显著提高4.67%~9.86%,植株硫含量较氯化钾处理显著提高19.13%。研究表明,施用杂卤石能够提高花生荚果质量及花生秧干质量,并促进花生对氮、钾、钙和硫的吸收,其中杂卤石处理花生吸硫量提高可能是其花生荚果质量较氯化钾处理显著提高的主要原因,而吸钙量和吸氮量的提高可能是杂卤石处理花生秧干质量较氯化钾、硫酸钾镁和硫酸钾处理显著提高的主要原因。