It has been suggested that there are several potential benefits of providing nitrogen to cereals via the foliage as urea solution. These include: reduced nitrogen losses through denitrification and leaching compared with nitrogen fertilizer applications to the soil; the ability to provide nitrogen when root activity is impaired e.g., in saline or dry conditions, and uptake late in the season to increase grain nitrogen concentration. Factors that influence the degree of foliar absorption in field conditions have not, however, been clearly defined and losses to the atmosphere and soil can occur. Foliar urea applications may also hinder crop productivity although the explanations for this vary, and include desiccation of leaf cells, aqueous ammonia and urea toxicity, biuret contamination and the disruption of carbohydrate metabolism. It has not yet been determined which one, or combinations, of these mechanisms are most important in field situations. When damage has not been severe, foliar urea applications have increased grain yield, particularly when applied before flag leaf emergence and when nitrogen availability is limiting. Increases in grain nitrogen content are often larger when applications of nitrogen fertilizers to the soil are reduced, and when the urea solution is sprayed either at anthesis or during the following two weeks. It is during this period that foliar urea sprays can be of greater benefit than soil applications with regard to nitrogen utilization by the crop. Increases in wheat grain nitrogen concentration following urea application can improve breadmaking quality. Responses in loaf quality may, however, be variable particularly when increases in grain nitrogen content have been large, and/or when the nitrogen: sulphur ratio in the grain is increased. These circumstances have lead to alterations in the proportions of the different protein fractions which influence breadmaking potential. To exploit the full potential benefits of foliar urea application to cereals, more needs to be known about the mechanisms, and thus how to prevent losses of nitrogen from the foliage, and to reduce the phytotoxic influences of sprays. More information is also required to exploit the reported effects that urea may have on limiting the development of cereal diseases

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Since the 1960s conventional crop breeding has increased food production commesurate with the growing population. For agricultural development to continue, the exploitation of greater genetic diversity and modern biotechnology are becoming increasingly important. This article reviews the milestones achieved by the Green Revolution and many of the recent breakthroughs of modern biotechnology.

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Comparisons of Maris Widgeon, an old taller breadmaking variety, were made with more modern varieties of wheat in eight successive field experiments between 1987/88 and 1994/95 at Harnhill Manor Farm, Cirencester, Gloucestershire, U.K. for grain yield, specific weight, protein concentration, SDS-sedimentation volume and Hagberg falling number. The effect of quality of the grain on financial value was investigated by applying a range of penalties for insufficient protein, Hagberg falling number and specific weight. Values for feed and breadmaking quality wheat were also varied. For all of the different pricing scenarios, grain from Maris Widgeon was of lower value than that from the most modern variety. The higher protein concentration of Maris Widgeon, in comparison with Hereward, was insufficient to compensate for lower yields and Hagberg falling numbers. Reduced height genes (Rhtl and Rht2) in isogenic lines of Maris Widgeon, studied in one field experiment, increased grain yield and Hagberg falling number but reduced protein content. Interactions of variety with other factors relevant to organic systems were also investigated namely undersowing (four seasons), defoliation by mowing or sheep grazing in Spring (three seasons), and sowing date (two seasons) but these factors had little impact on the relative grain performance of the varieties studied.