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In an experiment on green manuring started at Woburn in 1936, farmyard manure (FYM) was applied in alternate years until 1954 and straw similarly from then until 1963. Various green manures were grown from 1936 to 1953. From 1954 to 1963 ryegrass and trefoil were grown either each year or in alternate years; in 1964 and 1965 they were grown each year. After annual cropping without organic manuring the organic-C and total-N decreased from 0·86 per cent and 0·091 per cent respectively in 1936 to 0·76 percent and 0·082 per cent in 1966. Ploughing in straw alone approximately halved the loss. FYM and green manures both maintained the original percentages of soil C and N. The effect of FYM and straw applied together was approximately the sum of the effects of FYM and straw applied separately. Of the green manures ploughed in, trefoil returned the most nitrogen to the soil. Trefoil increased and ryegrass decreased the mineralizable-N in the soil. [ABSTRACT FROM AUTHOR]

Ammonium sulphate and calcium nitrate both containing excess 15N were applied to four acid sandy soils; two were from old arable fields and two from grassland, selected so that one of each pair was about pH 5 and the other about pH 6 (in water). The soils were incubated for 6 weeks at 21°C in large glazed earthenware pots, one set with the nitrification inhibitor 2-chloro-6-(trichloromethyl)-pyridine added and another without inhibitor. Ammonium and nitrate N were determined at intervals, and the total-N at the start and after 6 weeks. The atom per cent 15N in the mineral-N extracted from soils treated with ammonium sulphate was determined after 0, 3, and 6 weeks, and in the total-N of all the soils given N-fertilizer at 0 and 6 weeks. Much added N was immobilized at first, but some was re-mineralized during the second half of the incubation. Mineral-N extracted from soils treated with ammonium sulphate contained less 15N than the fertilizer added, showing that part of the apparent re-mineralization during the second half was from unlabelled soil organic matter. After incubating for 6 weeks less than 5 per cent of the N added as nitrate was lost but about 5 per cent of the labelled-N added as ammonium sulphate was lost from the two grassland soils. Adding the inhibitor prevented this loss. After incubating, the soil remaining in each jar was halved to provide duplicate pots and sown with ryegrass. A similar series of pots with the same treatments (but with unlabelled fertilizer) was also prepared from the soils that had been stored slightly moist and at 21°C; these were sown with ryegrass. All pots were harvested after 42 days and again after 70 days. More than 93 per cent of the labelled-N was recovered in plants and soil, except from the two grassland soils to which calcium nitrate was added. It is concluded that while a little nitrogen may be lost during nitrification in some of these soils, more nitrogen may be lost during the growth of grass, when nitrate is present in relatively large amounts. The nitrification inhibitor decreased yields of grass at the first cutting on grassland soils treated with ammonium, but increased them on soil treated with nitrate, suggesting that changing the proportions of nitrate to ammonium by adding the inhibitor alters the growth rate and yield of grass. [ABSTRACT FROM AUTHOR]

Urea supplying 100 1b of N/acre was either broadcast on the surface or mixed with four soils (two clay-loams, two sandy-loams) and losses of ammonia were measured when the soils were maintained at 40, 50, or 60 per cent water-holding capacity (WHC) and incubated at 5°or 25°C. Urea and ammonium sulphate were similarly applied to two calcareous soils at 40 per cent WHC and 5°or 25°C. Losses varied most among soils, from 2 per cent of the N applied from an unmanured clay-loam to 13 per cent from an unmanured sandy-loam. Changing temperature and water content affected losses little on average, but their effects differed with different soils. Losses of ammonia were similar from urea and from ammonium sulphate applied to the calcareous soils. Analyses at the end of the experiments showed that: (i) nitrite tended to accumulate in the sandy and calcareous soils, accumulation being favoured by lower temperature and wetter soil; (ii) ammonia was lost at 25° C from calcareous soils until all the ammonium- N had been nitrified, from the slightly alkaline clay soils until nine-tenths had been nitrified, and from the neutral sandy soils until half had been nitrified. [ABSTRACT FROM AUTHOR]

Factorial experiments were done to test the effects of N, P, and K fertilizers and lime on grain and straw yields. In addition, deep ploughing was compared with shallow, static with flowing irrigation, and in two Latin square experiments alternative P fertilizers were tested. Nitrogen fertilizers increased yields most on the most fertile soil type. Phosphorus fertilizers did not increase yields on the most fertile soil type, gave a moderate increase on the less fertile soils and prevented crop failure on soil containing much exchangeable Al. On the last soil type, water soluble phosphates were more effective than basic slag. Potassium fertilizers improved early growth at one site but did not increase straw and grain yields. Lime did not increase yields, even on the very acid soil containing much exchangeable Al. The weight of 100 whole grains was determined for rice from experiments sown with'pure-line'seed. Increased weight was normally found only when the field treatment increased yield. The N, P, K, and Ca contents of, and uptake by, straw and grain were determined for three sites with varying responses to applied N and P. Fertilizer N and K had little effect on the composition of straw or grain. Fertilizer P increased the P and decreased the N contents of straw and grain on P-deficientsoils. Fertilizer P also decreased K content of the straw, increased that of the grain at one site, and also increased the Ca content of straw and grain. Lime increased the Ca content of the straw and of the grain at one site. Uptake of nutrients was affected more by yield than by composition. [ABSTRACT FROM AUTHOR]

An attempt has been made to account for the different soil types which are derived from alluvial material of similar age and origin. The sequence noted was undifferentiated alluvium (frontland clay soil), humose clay (pegassy-clay soil), thin organic soils (pegasse). The subsoil varied from that similar to frontland clay to a bleached yellowish-white structureless clay. Differing durations and intensities of flooding were considered to be responsible for the changes in the subsoil. With permanent flooding, plant residues accumulate on the surface and the soil is more rapidly leached. Less organic matter accumulates and less leaching occurs with seasonal flooding. Reefs of dry sand and other soils develop under special conditions and, as they do not belong to the general sequence, are described separately. [ABSTRACT FROM AUTHOR]