Effects of magnesium on cereals, potatoes and leys grown on the 'continuous cereals' site at Woburn

Symptoms of magnesium deficiency and take-all disease occurred during 1967 in wheat grown for the second year in succession on the ‘Classical’ cereal site at Woburn. Magnesium fertilizers, which cured the deficiency symptoms and increased wheat yields in 1968 and 1969, had no effect on take-all. Leaves from crops severely attacked by take-all contained less nitrogen and potassium than leaves from unattacked plants but not less magnesium. In 1969 magnesium fertilizer did not increase yields or affect takeall of spring barley on the site but, in contrast to 1968, increased potato yields. Magnesium fertilizer improved the establishment of clover, especially on soil containing least magnesium. Soil analyses show a tenfold decline in exchangeable Mg since 1888. Losses were most from soil given ammonium sulphate and more from the site where wheat was long grown than where barley was. Differences in soil magnesium did not explain large differences in yields of potatoes or leys between blocks of the experiments. RESP-645