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The effect of applied cobalt on the cobalt content of pasture plants has been studied in pot, field, and laboratory experiments. The generally poor agreement between pot and field experiments may be partly due to the noted variation of cobalt status of pasture with season and the influence of waterlogging. Cobalt treatments were effective for at least 2 yr on the humus podzol soils, but there was only a residual effect for 1 yr on other soils. Alteration of the soil pH did not prove a satisfactory means of increasing cobalt status of pasture on soils where it was most required. The efficiency of cobalt fertilizers as a means of alleviating problems of cobalt deficiency depends on the manganese content of the soil. Plants grown on soils containing > 1000 p.p.m. of total manganese are unlikely to benefit from application of cobalt fertilizer to the soil, necessitating foliar application by sprays or the use of cobalt oxide pellets for stock.

SUMMARYThe C and N in the biomass of soils from eight grassland field experiments where lime had been applied was determined by the chloroform fumigation method. Lime application increased C and N in the biomass by approximately 30% overall, although there was no effect at two sites. In the unlimed plots basal CO2 production, biomass C, and flush of mineral N production (FN) increased with soil pH. Biomass C and FN were correlated with total N content but not with organic C.Differences in the apparent C/N ratio of the biomass were found in unlimed soils of pH ≤ 4·5 and in those of pH > 4·5, the ratios being 4·2 and 5·8 respectively. For limed soils the ratio was 5·2. It is probable that the chloroform fumigation method is not suited to soils of very low pH, and that the C/N ratio obtained in soils of pH < 4·5 is artificially low.

1. Forty-nine 33 factorial experiments in 1957–60 tested the response of sugar beet to 0·6,1·2, 1·8 cwt. N, 0·0,0·5,1·0 cwt. P2O5 and 0·8 1·6 2·4 cwt. K2O per acre. On forty-one of the sites, the experiment was repeated in the presence of 12 tons FYM per acre. There were also six trials in which the rates of mineral fertilizer had been altered to suit local conditions.2. Optimum dressings for sugar yield without FYM were 1·0 cwt. N, 0·5 cwt. P2O6 and 1·6 cwt. K2O per acre. This closely agrees with results of experiments made in 1934–39. Exceeding the optimum nitrogen dressing decreased sugar yield although the yield of tops was increased. The main value of dung for beet was in the N, P and K it provided. With FYM, optimum dressings were only 0·6 cwt. N, 0·0 cwt. P2O5 and 0·8 cwt. K2O per acre.3. Response to nitrogen differed greatly from field to field and the best guide to the nitrogen requirement of a field was the previous cropping. Beet which followed two or more cereal crops needed more nitrogen on average than beet which did not. Response to phosphate and potash did not differ much in different experiments and the national optimum would have been satisfactory for nearly all fields. The only use of soil analysis was to identify the very few fields which needed more than the average dressing of phosphate. The efficiency of phosphate and potash manuring could be slightly increased by taking soil type into account.

1. Twenty-nine experiments on sugar beet in 1957–59 compared ploughing-down of phosphate and potash in the previous autumn with spring application before the seed-bed preparations.2. On average, spring application gave a higher yield of sugar and tops than ploughing-down, both in the wet summers of 1957 and 1958 and in the dry summer of 1959.