W. P. Davies

Foliar urea fertilization of cereals: A review

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.

Effects of late-season applications of propiconazole and tridemorph on disease, senescence, grain development and the breadmaking quality of winter wheat

One glasshouse and six field experiments investigated the effects of propiconazole plus tridemorph fungicide treatments at flag leaf and/or ear emergence of winter wheat (Triticum aestivum L.) in the UK from 1984 to 1990. Fungicide effects on diseases, green leaf area and breadmaking quality of cv. Avalon were studied. Additionally, three of the field experiments investigated grain filling, drying, and nitrogen accumulation, and two of these experiments tested fungicide effects over different cultivars. When averaged over all cultivars, the fungicide significantly (p < 0.05) increased grain yield and thousand-grain weight (TGW) in five, and specific weight in three field experiments. Grain crude protein concentration (CP) and Hagberg falling number (HFN) were significantly reduced once following Septoria tritici control, and HFN alone was reduced a second time following powdery mildew (Erysiphe graminis f.sp. tritici) control. Despite reductions in CP and/or HFN, overall loaf quality was improved by fungicide application. Fungicide application increased the rate of grain filling rather than its duration and delayed grain drying. In 1985 and 1986 there were a number of cultivar × fungicide interactions, which further demonstrated that degree of control against S. tritici and powdery mildew were associated with effects on grain nitrogen content, mean grain weights and specific weights in different years. In the glasshouse experiment the fungicide controlled powdery mildew and significantly increased CP. It was concluded that recommendations on fungicide use, based on obtaining an economic yield response, do not need to be altered to take effects on breadmaking quality into account.

Quality and Value of Organic Grain from Contrasting Breadmaking Wheat Varieties and Near Isogenic Lines Differing in Dwarfing Genes

ABSTRACT 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 (Rht1 and Rht2) in isogenic lines of Maris Widgeon, studied in one field experiment, increased grain yield and Hagberg fa...

Disease development and senescence of the flag leaf of winter wheat in response to propiconazole

Fungicide applications to wheat have been reported to maintain the green area of the leaves (Dickinson & Walpole, 1975; Stevens & Palmer, 1980). It is not known, however, whether the photosynthetic rate of the leaves is also maintained. It was therefore decided to investigate disease development, green leaf area and photosynthesis of the flag leaf of winter wheat in response to the fungicide propiconazole, which has not previously been reported to influence senescence in the field.

Effects of spring nitrogen fertilizer on the Hagberg falling number of grain from breadmaking varieties of winter wheat

Hagberg falling number (HFN) is used to estimate alpha-amylase activity in wheat grain (Perten, 1964) and it is utilized by flour millers and the Intervention Agencies of the European Economic Community as a grain quality measurement for breadmaking (Anon. 1983). High nitrogen fertilizer application can lead to lodging and can decrease HFN (Brun, 1982). This may result from damp conditions around the ear encouraging germination, and therefore increasing alpha-amylase activity (Stewart, 1984). However, since nitrogen application can also delay maturity, it has been suggested that this influence could maintain high falling number (Anon. 1985). Pushman & Bingham (1976) found that increased nitrogen application decreased alpha-amylase activity, lending support to the previous suggestion, but contrasting with the results of Brun (1982).

The use of residual maximum likelihood to model grain quality characters of wheat with variety, climatic and nitrogen fertilizer effects

Year × variety means of wheat grain crude protein content (CP) and Hagberg falling number (HFN) surveyed in the UK from 1974 to 1993 were investigated with a residual maximum likelihood (REML) analysis using variety, nitrogen fertilizer application (kg N/ha), average monthly temperatures (°C), and total monthly rainfall (mm) as fixed terms, and year as a random term. Annual variety means were weighted according to the inverse of their variances. The statistical significance of fixed terms as they were added to the model was evaluated by comparing the Wald test statistic with critical values of chi-squared. CP, except for 1976 which was associated with prolonged drought conditions, was best described with a model combining effects for variety ( P < 0·001), nitrogen application rate (0·0143, S.E. = 0·00312, P < 0·001), July temperature (0·184, S.E. = 0·0582, P < 0·01) and May rainfall (−0·00952, S.E. = 0·00233, P < 0·001). A model describing HFN combined effects for variety ( P < 0·001), August rainfall (−0·930, S.E. = 0·2579, P < 0·001) and June temperature (24·4, S.E. = 7·37, P < 0·001). These models were evaluated for describing CP and HFN of cv. Avalon grown on sandy-loam from 1982 to 1992 at one site. Correlation coefficients of 0·51 ( P = 0·1) and 0·72 ( P = 0·012) were obtained between observed values at this site and those predicted from the nationally derived models for CP and HFN respectively. Variety effects suggested that the varieties commonly used in the mid 1970s would give higher CP and lower HFN than their more modern counterparts if grown at similar levels of nitrogen and in the same climatic conditions.

Organic wheat performance following conventional and non-inversion tillage systems

Field trials were conducted from October 2010 to August 2012 on land registered with the Soil Association, UK, for organic production on the Royal Agricultural Universitys Harnhill Manor Farm near Cirencester, UK, to compare the effects of conventional tillage (CT) involving maximum soil manipulation and 0% soil surface plant residues against conservation tillage strategy including low residue non-inversion tillage (LRNiT) involving minimal soil movements and 30% soil surface plant residues and also high residue non-inversion tillage (HRNiT) with least soil movements and maximum (>50%) retention of soil surface plant residues on organic winter and spring wheat performance. Establishment, growth and the yield response of organic winter and spring wheat for the three cultivation systems were assessed to determine the influence of these tillage treatments. Results showed that the plant establishment and tillers were significantly higher in CT than LRNiT and HRNiT in both cropping seasons. The total number of shoots, ear numbers, dry matter yield, 1000 grain weights and grain yield were significantly higher in the CT and LRNiT than HRNiT for winter wheat, whilst they were significantly higher in the CT than LRNiT or HRNiT for spring wheat. Crop establishment, growth and yield response were influenced by the weather conditions beyond the tillage treatments for the spring wheat compared with the winter wheat. On the basis of these results, a better alternative for CT could be LRNiT for winter wheat. Conversely, for spring wheat, CT had better crop establishment, growth and yield than other forms of cultivation.

Weed manifestation under different tillage and legume undersowing in organic wheat

Field experiments from October 2010 to August 2012 were conducted at the Royal Agricultural Universitys organic Harnhill Manor Farm near Cirencester, UK to explore tillage and legume undersowing effects on dry matter (DM) of broadleaf and grass weed infestation in organic winter and spring wheat. The experiments were designed using a randomized complete block with split plot arrangements. Tillage treatments involved conventional tillage (CT), low residue non-inversion tillage (LRNiT) and high residue non-inversion tillage (HRNiT) as main plots with undersowing white clover (WC), black medic (BM) or non-undersown (Nus) as subplots. In both cropping seasons, among tillage treatments, HRNiT had significantly higher total weed DM than CT or LRNiT. The mid-season assessments for weed species indicated HRNiT as having significantly higher grass weed DM than CT or LRNiT for both the wheat types. Broadleaf weed DM was significantly higher under CT than under LRNiT or HRNiT for winter wheat after GS61, whereas for spring wheat, broadleaf weed DM was significantly higher under CT than under HRNiT throughout the growing season. Undersowing had a significant effect only in spring wheat. Among undersowing treatments, WC had significantly lower total weed DM than BM. The broadleaf weed DM was significantly lower under WC than under BM or Nus. On the basis of these results, increasing the levels of tillage intensity with complete (0%) or minimal (30%) dispersion of soil cover appears to have decreased grass weed and total weed DM. Among undersowing treatments, WC seems to be a more reliable option than BM for spring wheat.