Effects of different Mg fertilizer sources on the magnesium availability in soils

Abstract

Pot experiments with different soils were conducted to determine the effect of different Mg fertilizer sources on magnesium availability. The sources studied included Kieserite ͑MgSO 4 H 2 O͒, a synthetic magnesium sulphate ͑SMS͒ with variable content of crystal water and a calcined magnesite ͑Mg-oxide͒. The three magnesium fertilizers vary greatly in their solubility in water, affecting the availability to plants once applied to the soil. Whereas Kieserite dissolved gradually and SMS immediately, Mg-oxide released only insignificant amounts of Mg in cool water ͑20°C͒ after intensive stirring. Due to the fact that these dissolution properties may distinctly affect Mg availability in soils, Kieserite as a standard magnesium source was tested against a slow release Mg-oxide in the fine and the coarse form. Soil extraction of samples taken from 0-10 and 10-20 cm depths at 4, 8 and 12 weeks after applying the fertilizers to the soil surface revealed that the rate at which Mg appeared in the available pool ͑CaCl 2 extracts͒ varied significantly between Mg sources. Mg availability from Kieserite was much greater than from Mg-oxide. Nutrient availability from Mg-oxide depended on the fineness of the material, i.e. the coarser the less available. Maize grown as test plant in the pots revealed a 10.6% larger yield and 19.6% larger Mg uptake in Kieserite than in Mg-oxide treated pots. High solubility of a fertilizer under high rainfall conditions, however, may also affect the Mg availability through large losses occurring by Mg leaching. Therefore, in a second experiment, the behaviour of surface applied magnesium fertilizers, Kieserite versus a quickly dissolving synthetic magnesium sulphate ͑SMS͒ was studied, using an Ultisol ͑Serdang Series soil from Malaysia͒. A simulation of high rainfall by excessive irrigation of 20 mm per day over a period of 16 days to a water saturated soil revealed that the amount of Mg lost by leaching differed between the two Mg sources tested. The lowest amount with 8.7% of the applied Mg was lost in the Kieserite treatment at the low application rate and the highest with 22.3% in the SMS treatment at the high application rate. It is concluded that a gradual but strong release to match plants requirements is the most desired characteristic to maximize crop uptake and minimize losses.

Assessing and understanding non-responsiveness of maize and soybean to fertilizer applications in African smallholder farms

“…A pot study of Osemwota et al (2007) with soils from southern Nigeria showed significantly greater uptake of Mg by maize for a soil with Ca:Mg ratio of 1 compared to 8; this result did not hold in field experiments and did not relate to differences in productivity. A pot experiment by Härdter et al (2004) illustrated a fourfold decrease in responses of maize production to NPK fertilizer when the Ca:Mg balance was raised from 1 to 10. Besides this, it is well known that crop demand for Mg changes largely under adverse conditions, and hence that the cation plays a prominent role in strengthening the tolerance of crops to various stresses ( Gransee and Führs, 2013 ).…”

Magnesium Fertilization Improves Crop Yield in Most Production Systems: A Meta-Analysis

“…Although exchangeable-Mg levels were the primary factors determining yield increases (Supplementary Tables S1 and S2), there were clear interactions between soil pH and fertilizer types ( Supplementary Table S3). Mg fertilizers are generally classified into rapidly released (Mg-R) and slowly released (Mg-S) types with distinct particle size and water solubility (Mayland and Wilkinson, 1989;Härdter et al, 2004;Loganathan et al, 2005). Mg-S releases slowly and improved yield more efficiently as compared to Mg-R ( Figure 8C).…”

Magnesium accumulation, partitioning and remobilization in spring maize (Zea mays L.) under magnesium supply with straw return in northeast China

“…The nutrient release characteristics from a Mg fertilizer source are important for the sustained supply of Mg to plants. Very slowly releasing sources may lead to a temporal undersupply, and very rapidly releasing sources may be prone to dramatic Mg losses by leaching . Moreover, Mg and Ca appear to have an antagonistic relationship.…”

“…Very slowly releasing sources may lead to a temporal undersupply, and very rapidly releasing sources may be prone to dramatic Mg losses by leaching. 43 Moreover, Mg and Ca appear to have an antagonistic relationship. 44 Excessive Ca in soil leads to Mg deficiency, which may result in nutrient imbalances, depress Mg uptake by crop root, and in turn its translocation to plant parts and finally affect yields of crop.…”