The pH of precipitation, and the concentrations in precipitation and depositions by precipitation of H +, major cations, N, S, and chloride were measured in bulk collectors at three sites in Eastern England. The Rothamsted site is 100 km from the coast in a semi-urban environment. The Saxmundham site is 13 km and the Woburn site 120 km from the coast; both are in rural environments. Precipitation is acidic at all three sites, with a pH of 4.3 at Rothamsted and 5.0 at Saxmundham and Woburn at present, but the pH has been increasing. Precipitation chemistry is chiefly contrdlled by sea-salts (Na, Mg, C1) and earth salts (K, Ca, Mg, NH4, NO3). Sea-salts dominate near the coast at Saxmundham, but earth salts become much more important inland at Rothamsted and at Woburn. The concentration and deposition of non-sea C1 are increasing at Rothamsted and Saxmundham, those of non-sea SO4-S are increasing at Woburn, and those of NO3-N are increasing at all of the sites. Precipitation acidity is associated chiefly with non-sea SO4, and only a little with NO 3 and non-sea C1, at Rothamsted and Woburn. At Saxmundham, no correlation between acidity and anions is observed, presumably because of the overwhelming effect of sea-salts,
Laboratory measurements of ‘available’ soil‐N were used to try and assess its effect on dry matter, N content, and N% of ryegrass grown in pots, of barley and wheat seedlings grown in boxes and of barley grain from field crops grown on soils without fertiliser‐N.
Mineral‐N in the fresh soil (Mineral‐Nfresh) and the increase when fresh or re‐wetted air‐dry soils were incubated (Δ Mineral‐Nfresh or Δ Mineral‐Nair‐dry) were all significantly correlated with yields and N contents of ryegrass, barley and wheat seedlings and barley grain. These soil‐N measurements were also significantly correlated with N% in barley grain and sometimes N in ryegrass and in barley and wheat seedlings. Δ Mineral‐Nair‐dry was significantly correlated most often. Soil‐N measurements were correlated better with N contents of crops than with yields of dry matter.
Urea has obvious advantages as a fertilizer because it contains much N (46 %), is readily soluble in water and can be manufactured cheaply. It is attractive therefore as a straight fertilizer and is potentially useful for making highly concentrated fertilizers rich in N. In 1956, Widdowson, Penny & Cooke (1960) compared granular urea (containing 4-5 % of biuret) with ammonium sulphate and with calcium nitrate for main-crop potatoes and for kale; dressings supplying more than 1-0 cwt N/acre delayed the emergence of potato shoots and greatly decreased numbers of kale and potato plants, and thus yield. In 1957, crystalline urea (containing less than 1 % of biuret) damaged germination only little and gave almost the same yield as ammonium sulphate. , Widdowson & Penny (1960 compared prilled urea (containing 1-5 % biuret) with ammonium sulphate, where each was combinedrilled at 0-25, 0-50 or 0-75 cwt. N/acre with spring barley seed. Urea supplying 0-5 cwt. N/acre or 0-75 cwt. N/acre (containing 1-9 and 2-8 lb. biuret/ aero, respectively) checked early growth, often badly, and some plants died. Ammonium sulphate checked growth much less and then only at 0 • 7 5 cwt.
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