Effects of soil type and nitrogen on the quality of autumn-sown malting barley

Abstract

This project was carried out over three years with harvests in 1988, 1989 and 1990. Its aims were to examine the effects of soil type, nitrogen source and nitrogen rate on grain yield and quality of autumn sown malting barley.

Available water capacity (AWC) was taken as the main parameter for describing soil type. Attempts were made to identify soil types which may give a good chance of achieving a malting premium, and to assess the feasibility of predicting nitrogen use so as to maximise margins over nitrogen costs. AWC was a very varied parameter with considerable overlap between the high and low classification groupings. Nevertheless, high AWC sites were more reliable producers of higher yields and lower grain nitrogen than low AWC sites. Curves fitted to the data showed, on average; 90 kg/ha N were needed to give the highest yield (5.84 t/ha) commensurate with grain nitrogen contents no higher than 1.75% N on the low AWC sites. At the high AWC sites, the values were 107 kg/ha nitrogen to give 6.44 t/ha. On both groups of AWC sites, cereals were the predominant previous crop.

There were no significant differences between the effects of nitrogen sources on grain yield. Urea gave significantly lower grain nitrogen than ammonium nitrate although the effect varied between seasons, drier seasons favouring lower grain nitrogen contents from urea. Many of the natural variables of the growing season, particularly rainfall during the grain filling period, affect yield and grain nitrogen content. This makes it impossible to accurately forecast nitrogen fertiliser requirement in the spring. This effect is further confounded by the effect the overall national annual rainfall has on the premiums. High and low rainfall in different regions of production have different effects on overall supply, eg. drought in East- Anglia will more severely affect total supplies and quality than drought in the South West.