MAGNESIUM, POTASSIUM, SODTUM AND CALCIUM CONTENTS OF HERBAGE AS INFLUENCED BY FERTILIZER TREATMENTS OVER A THREE‐YEAR PERIOD

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Abstract
Results are given showing the effects of applying nitrogen, phosphorus, potassium, sodium and magnesium on the yield and mitieral composition of herbage cut repeatedly at the silage stage over a 3‐year period. Grasses and clovers were separated before analysis. A combination of nitrogen and potassium was essential for the maintenance of high yields. Superphosphate did not increase dry‐matter yields. 4 cwt. of common salt was ineffective, even under conditions of acute potassium deficiency; it reduced responses to potash and decreased yields when given with potash.Ammonium sulphate and common salt greatly increased sodium uptakes and muriate of potash depressed them. Potassium contents were greatly reduced by repeated nitrogen applications and muriate of potash gave consistent and significant increases. Potassium‐deficient grasses contained more sodium than potassium.Ammonium sulphate increased magnesium contents and muriate of potash reduced them. There was a marked tendency for both effects to be more significant in late‐season cuts. In late May the effects were small. 22 and 44 Ib. Mg/acre as magnesium sulphate had variable effects on herbage magnesium. These changes are discussed in relation to hypomagnesaemia.None of the fertilizer treatments altered the calcium contents of either grass or clover.