Comparisons of kieserite and calcined magnesite for sugar beet grown on sandy soils

Abstract

Twenty-three experiments between 1968 and 1971 compared the effect of no magnesium, 50 and 100 kg/ha magnesium as kieserite and 100 and 200 kg/ha magnesium as calcined magnesite, on yield and magnesium uptake by sugar beet. On average, 100 kg/ha magnesium as kieserite increased the mean sugar yield of 7-55 t/ha by 0-17 t/ha whereas 200 kg/ha magnesium as calcined magnesite increased it by only 0-08 t/ha; on fields with less than 15 ppm exchangeable magnesium the magnesium fertilizers increased sugar yield by 0-34 and 010 t/ha respectively and there was no response to either fertilizer when the soil contained more than 25 ppm of exchangeable magnesium.100 kg/ha magnesium as kieserite or calcined magnesite increased magnesium in the dry matter of tops by 0-091 and 0-040 % and of roots by 0-013 and 0-004 % respectively. Giving 100 kg/ha magnesium as kieserite or calcined magnesite increased uptake of the element in August by 5-1 and 2-6 kg/ha respectively. Differences in soil pH did not influence the uptake of magnesium from kieserite but they greatly affected uptake from calcined magnesite. On the slightly acid soils, the fertilizers were almost equally effective but at pH > 7-6 little magnesium was taken up from calcined magnesite. Glasshouse experiments showed that grinding the calcined magnesite increased the availability of the magnesium. INTRODUCTIONexperiment (Allcroft, 1960), 250-500 kg/ha calcined magnesite was found to be enough to prevent hypoPrevious experiments (Tinker, 1967; Draycott & magnesaemia, but in another experiment on a more Durrant, 1969) have shown that spring applica-alkaline soil it gave a much smaller response, tions of kieserite (MgSO 4 .H 2 O) largely prevented McConaghy et al. (1963) showed that calcined magnesium-deficiency symptoms and increased magnesite slightly increased magnesium in herbage, sugar-beet yield where the soils contained small but was not sufficient to prevent a deficiency of amounts of exchangeable magnesium. During the magnesium in blood serum of dairy cows. The last 4 years, calcined magnesite (largely MgO) has efficiency of calcined magnesite was improved by been imported in increasing quantities from Spain grinding. Hooper (1967) showed that the effect of as an alternative magnesium fertilizer for sugar calcined magnesite on the magnesium content of beet and other arable crops. Calcined magnesite has herbage was linearly related to soil pH -its magseveral attractions compared with kieserite, for it is nesium was readily available in acid but not in more concentrated (55 % Mg compared with 16 %), alkaline soils. cheaper (magnesium in calcined magnesite is aboutIn experiments testing response to kieserite and half the cost of the same weight in kieserite) and calcined magnesite for wheat and barley, Charlesmagnesite blends easily with other fertilizers.worth (1967) found that calcined magnesite deMost experiments comparing calcined magnesite creased deficiency symptoms and increased yield of with other magnesium fertilizers have been on grass-wheat more than kie...

Magnesium availability from kieserite and calcined magnesite on five soils of different pH

“…Batches of commercial calcined magnesite may vary in their particle size distribution, but are mainly granules rather than powder. From looking at uptake ratios for commercial calcined magnesite compared to kieserite, Draycott & Durrant (1972) gave relative availabilities of 0.74 at pH 6.6-7.0, 0.42 at pH 7.0-7.5 and 0.09 at pH>7.5; a far greater pH effect than our measured values in soil.…”

“…In theory a decrease of pH by 1 unit will increase the Mg solubility of calcined magnesite one hundredfold (Lindsay, 1973). Table 4 suggests some increase in recovery from the calcined magnesite in the lower pH, non-calcareous soils, hut the effect is much smaller than reported by Durrant & Draycott (1972). In this work, the particle size appears to limit solubility more than the small range of pH; physical disintegration of the granules produced by shaking for 22 h seems to make far more Mg available than incubation with soil for 25 months.…”

“…The recovery from granular (1-3 mm) calcined magnesite was only 20-41% after 25 months (Table 4). Recovery from the powder was much greater (64-84%), an effect also noted by Draycott & Durrant (1972). However, working with maize, Mordvedt and Kelsoe (1988) found that 1.4-2.0 mm granules of magnesium oxide were almost as effective as the powder but with larger granules, effectiveness decreased in proportion to their size.…”