Liquid manure as a grassland fertilizer: II. The response to winter applications

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Abstract
1. The effect of applications of liquid manure during the winter months was studied and compared with the application of dry artificial fertilizers on six different swards in two experiments in each of the years 1960, 1961 and 1962.2. The liquid manure supplied an average of 69 lb. N and 114 lb. K/acre at each application and plots received one dressing only applied in November, December, January, February or March. Further treatments consisted of applying conventional dry fertilizer supplying the same weight of nitrogen and potassium as the liquid manure and applied on the same day. A control plot received no added fertilizer or liquid manure.3. All plots were cut in May and a second cut was made 8–10 weeks later to measure residual effects of treatments.4. The maximum increase in dry-matter yields at cut 1 occurred with the February application although the January and March applications gave only slightly lower yields. The dry-matter yield/lb of N applied even from some November applications was comparable to the response obtained from applications of inorganic nitrogen made in summer in earlier experiments by other workers.5. The production of crude-protein followed a similar pattern to that of the dry-matter, and the maximum increase was from the March application.6. With similar rainfall conditions but different winter soil temperatures a mixture of Italian and perennial rye-grasses under average fertility conditions gave the highest response to liquid manure. This was followed by the later growing cocksfoot sward and the permanent pasture, on both of which yields were increased by all the monthly applications. The two swards containing grass and clover mixtures showed a response to the later dressings whereas a vigorous Italian rye-grass ley in the mild winter of 1961 was unaffected by treatment.