Assessing the need of maincrop potatoes for late nitrogen by using isobutylidene di-urea, by injecting trification inhibitors with aqueous N fertilizers and by dividing dressings of ‘Nitro-Chalk’

Abstract

SummaryIn experiments with maincrop potatoes at Rothamsted in 1976, 1977 and 1978 ‘Nitro-Chalk’ was broadcast, either as a single dressing on the seed bed, or half on the seed bed and half at tuber initiation. Isobutylidene di-urea was broadcast on the seed bed and aqueous ammonia was injected into the seed bed, without a nitrification inhibitor or with either ‘N-Serve’ (nitrapyrin) or sodium trithiocarbonate; all were compared with ‘Nitro-Chalk’ at rates of 200 or 300 kg N/ha. Additionally, single dressings of ‘Nitro-Chalk’ supplied 150, 250, 350 and 400 kg N/ha. In similar experiments at Woburn in 1979 and 1980 aqueous urea replaced aqueous ammonia and the additional amounts of ‘Nitro-Chalk’ (100 and 400 kg N/ha) were tested as both single and divided dressings. Winter wheat was grown in each of the following years to measure residual effects.Retaining half of the total N dressing of 200 or 300 kg N/ha as ‘Nitro-Chalk’ until tuber initiation improved yields at Rothamsted in 1976 and 1978 when irrigation was applied but not in 1977 when it was not. Dividing the N at Woburn improved yields at 100 and 400 kg N/ha but not at 200 or 300 kg N/ha. At Rothamsted injected aqueous ammonia was on average similar in effect to the undivided ‘Nitro-Chalk’ dressing at 300 kg N/ha, but less effective at 200 kg N/ha. In 1977, the wettest summer, it was, however, the most effective of the N-sources, provided that an inhibitor had been applied with it. At Woburn, injected aqueous urea did not differ consistently in effectiveness from ‘Nitro-Chalk’ and inhibitors did not improve its performance. Isobutylidene di-urea (IBDU) gave the smallest yields at both farms, apparently because it was too slowly available. Tuber size distributions were affected little by the amount or the form of N.IBDU residues increased wheat yields the most following the potatoes at Rothamsted. This apart, the N-sources had similar residual values.

Potato Response to Nitrogen Form and Nitrification Inhibitors

“…Tuber yield and quality reductions were also seen in a 2-year Texas study where N sources included ammonium sulfate, urea, or sulfur-coated urea (Vendrell et al 1981). These results are in contrast to other studies that showed either no change in crop yield or quality (Potter et al 1971;Penny et al 1984;Sahota and Singh 1984;Vos 1994), or in some cases, yield increases or increases in apparent recovery of the fertilizer N applied by the tubers (Roberts 1979;Sahota and Singh 1984;Wadman et al 1989;Bailey et al 1992;Martin et al 1993).…”

Growth, nitrogen uptake and partitioning within the potato (Solatium tuberosum L.) crop, in relation to nitrogen application

“…In the present study, withholding half the fertilizer nitrogen until after tuber initiation had no effect on either nitrogen uptake or tuber yield, except when comparing the divided and single applications of 20 g N/m a in 1984. Similarly, Penny, Addiscott & Widdowson (1984) found only slight yield increase in response to divided application of nitrogen, with consistent increase being obtained only when irrigation was also applied.…”

Comparative Effectiveness of Ordinary and Coated Urea and Nitrification Inhibitor Treated-Urea as a Source of Nitrogen for Maize

“…Maximizing the efficiency of applied fertilizers which show a poor recovery rate in tropical soils came under sharp focus after the oil crisis of 1973-74. Considerable progress has been achieved in the manufacture and use of slow release nitrogenous fertilizers in the western world (Hummel and Waddington, 1984;Keeney, 1982;Penny et al, 1984), but progress in warmer regions is less satisfactory. This investigation compares the effectiveness of ordinary urea, sulphur-coated urea, and ordinary urea blended with two nitrification inhibitors, neem (Azadirachta indica) cake and AM (2-amino-4-chloro-6 methyl pyrimidine), as sources of nitrogen for field-grown maize.…”