Effects of tillage and nitrogen fertilisation on triticale grain yield,chemical composition and nutritive value

BACKGROUND: Given the interest in the development of cultivation systems with low agronomic input and environmental impact, the aim of this study was to determine the influence of tillage system (conventional tillage (CT), two‐layer tillage (TT), surface tillage (ST) and minimum tillage (MT)) and nitrogen (N) fertilisation rate (0, 50 and 100 kg ha^?1) on triticale grain and protein yields, chemical composition and nutritive value. RESULTS: There were no significant differences among tillage treatments in grain and protein yields. ST resulted in significantly higher crude protein (CP) and true soluble protein (TSP) contents as well as in vitro crude protein digestibility (CPD). Neutral detergent fibre concentration was significantly higher with ST than with MT, and this led to a small reduction (2 g kg^?1 dry matter (DM)) in in vitro true DM digestibility (IVTDMD). N fertilisation significantly increased grain and protein yields as well as CP, non‐protein nitrogen and TSP contents and CPD. IVTDMD was significantly lower with 0 kg N ha^?1 than with 50 and 100 kg N ha^?1. CONCLUSION: Reducing tillage intensity improved the CP content and CPD of triticale grain. The application of 50 kg N ha^?1 resulted in good grain quality parameters and grain and protein yields. Copyright © 2010 Society of Chemical Industry     

Effects of eight tillage treatments on a tropical alfisol: Maize growth and yield

The effects of eight methods of preplanning tillage systems were investigated on maize growth and yield for eight consecutive crops grown from 1980 to 1983 on an Alfisol in south-west Nigeria. The tillage systems were: (A) no-till with residue mulch, (B) no-till with chiselling in the row zone to 50 cm depth, (C) mouldboard ploughing followed by (fb) harrowing, (D) disc ploughing fb rotovation, (E) no-till without residue mulch, (F) mouldboard ploughing at the end of rains, (G) mouldboard ploughing fb two harrowings with residue mulch (H) mouldboard ploughing fb two harrowings and ridging. In seasons with infrequent rains and long dry spells, seedling emergence was significantly suppressed on ridged plots (treatment H). The 1500 h soil temperature on the ridged seedbed (H) at 5 cm depth exceeded 40°C, and was about 10°C more than in no-till with mulch (A). The oxygen diffusion rate (ODR) at 10 cm depth was the most in the no-till mulch and the least in the furrow bottoms. The soil moisture reserve was larger in the no-till plots than in the ploughed treatments. Plant height and vigour were adversely affected on ridges in seasons with frequent dry spells. In these seasons, maize grain yield declined with the increasing intensity of mechanical tillage. For the eight seasons, the cumulative benefits in grain yield of all the no-till treatments were 1.76 and 0.32 tonnes ha^?1 in comparison with ridges (H) and ploughed (C, D, F, G) treatments, respectively. The mean seasonal yield was 3.37 and 1.00 t ha^?1 for the first and second seasons respectively. The seasonal fluctuations in grain yield were related to rainfall amount and the length of growing season.     

Mulching an ultisol in southern Nigeria: Effects on physical properties and maize and cowpea yields

A study carried out for two cropping seasons at Nsukka, southeastern Nigeria, to determine the minimum rate of straw mulch for optimising the physical conditions of the topsoil (0–20 cm depth) of a fragile ultisol and maize (Zea mays L) and cowpea (Vigna unguiculata L Walp) yields, found that soil water sorptivity, transmissivity, steady state infiltration rate, cumulative infiltration after 90 min and time to attain steady state infiltration were optimal at the 2.0 t ha^?1 mulch rate. Also, at this rate of mulching, water retention and per cent water-stable aggregates > 0.5 mm were maximal whereas soil compaction (measured by dry bulk density) was minimal. Between 2 and 10 days after saturation the surface soil had reductions of 11, 6, 6 and 6% in volumetric water content, respectively, on the control (0), 2.0, 4.0 and 8.0 t ha^?1 mulched plots, mainly due to evaporation. Supra-optimal soil temperatures (> 30°) were observed only on the bare plots whereas no significant differences in maximum soil temperature among the mulched plots were noticed. Maize and cowpea yields were optimal at the 4.0 t ha^?1 rate with respective increases over the bare plots of 80 and 67% at this rate.     

Effects of nitrogen fertiliser on yield,dry matter content and flouriness of potatoes

The effects of incremental amounts of nitrogen fertiliser in the range 0–200 kg ha^?1 on yield ha^?1, tuber dry matter (DM), DM ha^?1and flouriness were evaluated in five potato cultivars over three seasons. In general, yield increased with the use of up to 100–150 kg N ha^?1and remained constant thereafter; % DM of tubers was significantly diminished by amounts of nitrogen > 150 kg ha^?1. In a single poor growing season, yields were small and both yield and% DM were less affected by nitrogen. The mean flouriness score of cooked tubers was highly correlated with specific gravity (SG) class (r = 0.94); tubers with SG > 1.08 were scored floury to very floury. Moderate nitrogen fertiliser use (? 100 kg ha^?1) had little effect on weight per cent of crop > SG 1.08; large amounts of N (200 kg ha^?1) resulted in a substantial decline in the size of this fraction; the effects of intermediate amounts varied with season and cultivar.     

Long‐term impact of nitrogen and potassium fertilizers on yield,soil nutrients and biochemical parameters of tea

A field experiment was conducted with tea cultivar UPASI‐9 over a period of 9 years to evaluate the long‐term effects of nitrogen (N) and potassium (K) fertilizers on yield, biochemical parameters, soil and leaf nutrient status. The yield increase was as high as 66% over the control for N application of 450 kg ha^?1 year^?1. Polyphenol and amino acid contents increased with increase in K application rate. Positive and significant correlation was found between nitrate reductase activity and the amino acid content of the tea shoots. While ammoniacal nitrogen in the soil was not affected by the application of fertilizer, ammonium acetate extractable K increased. The failure to apply fertilizer resulted in depletion of the organic matter status of the soil. Although increased rate of nitrogen application increased the overall yield of made tea (kg ha^?1 year^?1), the specific yield (kg kg^?1 N) declined. The soil tended to become acidic from frequent application of high doses of nitrogenous fertilizer. The leaf NK status was significantly influenced by the various treatments. Copyright © 2004 Society of Chemical Industry     

Control of speargrass (Imperata cylindrica (L) Raeuschel) with glyphosate and fluazifop‐butyl for soybean (Glycine max (L) Merr) production in savanna zone of Nigeria

A field trial was conducted in 1996 and 1997 to control speargrass (Imperata cylindrica (L) Raeuschel) for soybean production. The treatments comprised four levels of glyphosate, 1.08, 1.44, 1.80 and 2.16 kg ha⁻¹, applied pre‐tillage and followed by one hoe‐weeding (HW) at 6 weeks after planting (WAP); fluazifop‐butyl, 0.125, 0.25 and 0.375 kg ha⁻¹, at 3WAP; 1HW at 3WAP; 2HW at 3 and 6WAP; and an unweeded control. Glyphosate and fluazifop‐butyl controlled 57–85% and 51–83% respectively of I cylindrica compared with 64–67% by traditional hoe‐weeding. The highest grain yield (1.88 t ha⁻¹) was obtained from plots treated with glyphosate (1.44 kg ha⁻¹) + 1HW. The highest profit, however, was obtained with fluazifop‐butyl. It was unprofitable to apply glyphosate at rates higher than 1.44 kg ha⁻¹ to control I cylindrica at 30 cm foliage. © 2000 Society of Chemical Industry     

Some relationships between grain yield and grain protein of wheat experiments in south-east england and comparisons with such relationships elsewhere

By adopting a uniform method of presentation, the interrelationship between grain yield, %N in grain and N uptake (or protein yield) from diverse experiments and surveys can be compared readily. All three variables can be shown together by plotting yield vs %N and adding the third variable in the form of hyperbolic lines representing equal N uptake (or protein yield). This method is used in two diagrams which display 2000 values derived from 124 experiments on winter wheat and 400 values from 41 experiments on spring wheat, conducted by Rothamsted Experimental Station over 20 years. Both scatter diagrams display well-defined boundaries which have been emphasised by linking points along these boundaries to form ‘envelope curves ’For winter wheat the maximum yield was 9.5 t ha^?1, the largest N concentration about 3% and the largest N uptake 170 kg N ha^?1 (about 970 kg protein ha^?1). Spring wheat had a maximum grain yield of 6.3 t ha^?1, the largest N concentration was 3.1% and the largest N uptake 125 kg N ha^?1. Four examples of other work set within the same framework show applications of our method of presentation. Results from a recent more homogeneous series of experiments in southern England (conducted by the Agricultural Development and Advisory Service), showing clear seasonal differences, are seen to lie within the envelope curve defined by the Rothamsted experiments. Further illustrations are taken from an experiment by the Plant Breeding Institute, Cambridge, comparing varieties of different bread-making qualities, from work of the Nebraskan plant breeding team who have produced grain with larger protein content without sacrificing yield, and from survey data for England and West Germany.     

Tillage and mulching effects on water use,root growth and yield of rainfed mustard and chickpea grown after lowland rice

Crops grown under rainfed conditions are prone to water stress, owing to rapid loss of soil moisture and development of mechanical impedance to root growth. The stress can be alleviated by enlarging rooting volume in the soil and/or by regulating the supply of soil moisture. This study reports the effects of zero, minimum and conventional tillage with and without rice straw mulch on conservation of soil moisture, root growth and yield of chickpea and mustard grown under rainfed conditions for three years (1990–91 to 1992–93) in a deep clayey soil (Typical Chromusterts). Minimum tillage, with or without straw, enhanced soil moisture conservation and moisture availability during crop growth. As a consequence, the root mass, yield components (plant stand, number of pods per plant and plant height) and grain yield increased. Availability of soil moisture during the crops growth period, maintained better plant water status. Zero tillage was superior to the other tillage practices for mustard. On the other hand, chickpea grain yield was statistically similar for zero tillage and minimum tillage. Straw mulch conserved more water in the soil profile during the early growth period compared to no mulch. Subsequent release of conserved soil water regulated proper plant water status, soil temperature, and lowered soil mechanical resistance, leading to better root growth and higher grain yield of both chick-pea and mustard in straw mulch than in no mulch plots. © 1998 Society of Chemical Industry     

The effects of irrigation,nitrogen fertilizer and grain size on Hagberg falling number,specific weight and blackpoint of winter wheat

The effects of irrigation and nitrogen (N) fertilizer on Hagberg falling number (HFN), specific weight (SW) and blackpoint (BP) of winter wheat (Triticum aestivum L) were investigated. Mains water (+50 and +100 mm month^?1, containing 44 mg NO₃^? litre^?1 and 28 mg SO₄^2? litre^?1) was applied with trickle irrigation during winter (17 January–17 March), spring (21 March–20 May) or summer (24 May–23 July). In 1999/2000 these treatments were factorially combined with three N levels (0, 200, 400 kg N ha^?1), applied to cv Hereward. In 2000/01 the 400 kg N ha^?1 treatment was replaced with cv Malacca given 200 kg N ha^?1. Irrigation increased grain yield, mostly by increasing grain numbers when applied in winter and spring, and by increasing mean grain weight when applied in summer. Nitrogen increased grain numbers and SW, and reduced BP in both years. Nitrogen increased HFN in 1999/2000 and reduced HFN in 2000/01. Effects of irrigation on HFN, SW and BP were smaller and inconsistent over year and nitrogen level. Irrigation interacted with N on mean grain weight: negatively for winter and spring irrigation, and positively for summer irrigation. Ten variables derived from digital image analysis of harvested grain were included with mean grain weight in a principal components analysis. The first principal component (‘size’) was negatively related to HFN (in two years) and BP (one year), and positively related to SW (two years). Treatment effects on dimensions of harvested grain could not explain all of the effects on HFN, BP and SW but the results were consistent with the hypothesis that water and nutrient availability, even when they were affected early in the season, could influence final grain quality if they influenced grain numbers and size. Copyright © 2004 Society of Chemical Industry     

Effect of drought and irrigation on the fate of nitrogen applied to cut permanent grass swards in lysimeters: Nitrogen balance sheet and the effect of sward destruction and ploughing on nitrogen mineralisation

Fuor years after ¹⁵N labelled fertiliser nitrogen (as Ca(NO₃)₂ and equivalent to 400 kg N ha^?1) was applied to permanent grass swards growing in lysimeter monoliths, approximately one-quarter remained immobilised in soil organic matter. In the intervening years similar but non-labelled applications were made. Although differing rainfall regimes applied during the experiment had significantly affected nitrogen uptake by plants and nitrate loss in drainage, they caused no significant effect on the tracer nitrogen remaining in the soil, the ranges were 85–97 kg N ha^?1 and 79–94 kg N ha^?1 respectively for the 135 cm deep clay and silt loam soil monoliths. Labelled nitrogen unaccounted for in crop, drainage or soil was presumed to have been denitrified. These losses averaged 62 and 49 kg N ha^?1 on the clay and silt loam soils respectively; again the differing rainfall regimes caused no significant differences. The ratio between estimates of labelled nitrogen denitrified and of annual nitroux oxide loss was approximately 9:1 for both soils. The conversion from permanent grass to winter wheat in autumn 1981, involving killing and then burying the sward, resulted in no pronounced increase in net mineralisation of labelled nitrogen. However, the balance between crop uptake and the quantity leached did change. Labelled nitrogen assimilated was less for the wheat (growing without addition of fertiliser nitrogen) than for the grass in its last year, and the quantity leached was considerably greater than under grass swards that were supplied with an average rainfall distribution. Following the first wheat harvest total nitrogen leached averaged 51 and 44 kg N ha^?1 on the clay and silt loam soils respectively. Rates of nitrous oxide emissions during the autumn following sward destruction were greater than in earlier years, but this enhanced loss was of short duration. The crop clearly benefited from the succession of nitrogen applications made to grass, as grain yield and total nitrogen uptake exceeded 7 t ha^?1 and 120 kg N ha^?1 respectively on both soils. These quantities exceed the national averages for winter wheat and are also considerably greater than for crops from lysimeters which received no nitrogen fertiliser throughout the experiment.     

Quality of white cabbage yield and potential risk of ground water nitrogen pollution,as affected by nitrogen fertilisation and irrigation practices

BACKGROUND: The effect of different fertilisation (broadcast solid NPK application and fertigation with water‐soluble fertiliser) and irrigation practices (sprinkler and drip irrigation) on yield, the nitrate content in cabbage (Brassica oleracea var. capitata L.) and the cabbage N uptake was detected, in order to assess the potential risk for N losses, by cultivation on sandy–loam soil. The N rate applied on the plots was 200 kg N ha^?1. RESULTS: The highest yield (93 t ha^?1) and nitrate content (1256 mg kg^?1 DW) were found with treatments using broadcast fertilisation and sprinkler irrigation. On those plots the negative N balance (?30 kg N ha^?1) was recorded, which comes mainly from the highest crop N uptake (234 kg N ha^?1) indicating the lowest potential for N losses. CONCLUSION: In terms of yield quality and the potential risk for N losses, broadcast fertilisation combined with sprinkler irrigation proved to be the most effective combination among the tested practices under the given experimental conditions. The importance of adequate irrigation is also evident, namely in plots on which 50% drip irrigation was applied, the lowest yield was detected and according to the positive N balance, a higher potential for N losses is expected. Copyright © 2011 Society of Chemical Industry     

The influence of two soil nitrogen levels on the utilisation of 15N-labelled ammonium nitrate by ryegrass

In a field plot experiment with grass under cutting management, two soil organic nitrogen levels (0.92% and 1.14% in the top 75mm of soil) were created by repeated applications of pig slurry over a period of 8 years. The influence of soil organic nitrogen level on the recovery by ryegrass of ammonium nitrate fertiliser was then studied by reseeding the plots and applying ¹⁵N-labelled fertiliser at four rates (40, 80, 120, 160kg N ha^?1). After each of the first four cuts unlabelled ammonium nitrate fertiliser was applied at these same rates. The percentage utilisation of the labelled fertiliser was measured in five harvests over 2 years. At the first cut the percentage utilisation averaged 46.4% and was independent of fertiliser rate and soil organic nitrogen level. The average percentage utilisation values in cuts 2, 3, 4 and 5 were 9.9, 2.4, 0.8 and 0.5 respectively. For the total of all cuts it was only at the 40 kg N ha^?1 fertiliser rate that the percentage utilisation was significantly different (P<0.05) between the 0.92% and 1.14% soil organic nitrogen levels, at 49.0% and 61.4% respectively. The soil nitrogen contribution to ryegrass at the first cut was significantly increased (P<0.05) by the high soil organic nitrogen level at the 40 and 160 kg N ha^?1 fertiliser rates. Over all fertiliser rates the average soil nitrogen contribution to the first cut was 50.4 and 61.1 kg N ha^?1 at the 0.92 and 1.14% soil organic nitrogen levels respectively. From the first cut data, soil organic nitrogen was estimated to have a net mineralisation rate of 2.6% year^?1 and a half-life of 26 years.     

The nitrogen content of potato (Solanum tuberosum L.) tubers in relation to nitrogen application—the effect on amino acid composition and yields

The effect of nitrogen application on the nitrogen content and yield of amino acids from potato tubers was studied in one experiment in 1983 and two in 1984. Increasing fertiliser N over the range 0–250 kg ha^?1 raised tuber nitrogen concentrations from 0.68–0.81 to 1.27–1.49% DM. Applying half the fertiliser on the seedbed and half at tuber initiation did not increase tuber nitrogen concentrations compared with a single broadcast application at planting. Increasing tuber nitrogen concentrations had little effect upon the proportion recovered in amides or the different amino acids. Yields of some nutritionally essential amino acids were, therefore, substantially increased up to a maximum of 256 kg ha^?1 in 1982 and 308 and 384 kg ha^?1 in 1984 at the highest fertiliser level. These yields were significantly higher (P<0.01) than those found with the nitrogen application rate optimal for tuber dry matter production (213, 195 and 331 kg N ha^?1, respectively) in the same experiments. Methionine and cystine were the limiting essential amino acids. As the amount of each amino acid contained in a unit weight of fresh tuber increased with nitrogen supply, application of more nitrogen than is needed for maximal tuber dry matter production increased protein yields without decreasing the nutritional quality.     

Uptake of foliar-applied urea by winter wheat (Triticum aestivum): The influence of application time and the use of a new 15N technique

A new ¹⁵N technique (termed the negative discard method) for measuring recovery of foliar-applied N by crops in the field is described. ¹⁵N-labelled fertiliser solution is sprayed on to a small area of crop, using a hand sprayer, while the surrounding area is sprayed with unlabelled N at the same rate. An area considerably larger than that given ¹⁵N is harvested with a small-plot combine-harvester, and crop recovery of foliar-applied N is calculated from the ¹⁵N enrichment of the resulting sample containing a mixture of labelled and unlabelled material. The technique was used to measure recovery of N from ¹⁵N-labelled urea solution sprayed on to winter wheat (Triticum aestivum L cv Avalon) at six different times from growth stage 39 (3 weeks before anthesis) to growth stage 73 (2 weeks after anthesis). Each treatment of 40 kg N ha^?1 was divided into two equal portions, the second being applied 1–2 days after the first, to minimise the risk of leaf damage. The crop had earlier received 210 kg N ha^?1, as ‘Nitro-Chalk’, in spring (50 kg ha^?1 at growth stage 22 and 160 kg ha^?1 at growth stage 31) which was more than sufficient to achieve maximum grain yield. At harvest, 70% of the foliar-applied N given at anthesis (growth stage 65) was recovered in the above-ground crop, including 64 % in grain. The proportion of labelled N recovered in the grain (92% of that in the above-ground crop) was slightly greater than with soil-applied N given earlier in the growing season. Recovery of foliar-applied N was slightly less for the earliest (growth stage 39) and latest (growth stage 73) times of spraying: 64% and 58% in above-ground crop, and 56% and 54% in grain, respectively. All of the foliar applications of 40 kg N ha^?1 increased %N in grain to the same extent as an additional 40 kg N ha^?1 applied to soil in spring.     

Relationship between N concentration of grain and grain yield in recent winter-wheat experiments in England and Belgium,some with large yields

Eight winter-wheat experiments conducted by Rothamsted on clay soils in 1980 and 1981 formed part of an inter-institute collaborative programme on yield variation. The tests included no N and four amounts of fertiliser N up to 200 kg ha^?1, with and without spray treatments to control pests and diseases. Large grain yields—in excess of 10 t ha^?1—were often obtained, mainly where losses had been limited by sprays. In Belgium, 10 experiments during the same seasons were on a wider range of soils and had spray treatments applied to all plots. Yields exceeding 10 t ha^?1 were obtained at one site. Graphs showing the inter-relationship between grain-N %, grain yield and N uptake are used to compare the recent results with those from a 20-year study of similar data from 124 earlier Rothamsted experiments. The envelope curve delineating the range of yield and grain-N % values from these older experiments enfolded most of the more recent data points, except those deriving from the largest yields which were associated almost entirely with grain-N % values below the minimum recommended for British breadwheat. The largest grain-N uptakes were 180–190 kg ha^?1 and 170–180 kg ha^?1 in the recent Rothamsted and Belgian experiments respectively, compared with 160-170 kg in the older experiments. The linear or near-linear relationship between grain-N % and amounts of fertiliser N, established in the 20-year study, was again observed in the recent Rothamsted and Belgian experiments, with about 38 kg of added N needed to increase grain-N concentrations by 0.1%.     

Interrelationship between nitrogen concentration in grain,grain yield and added fertiliser nitrogen in wheat experiments of South-east England

Results from 20 years of wheat experiments were used to compare responses of grain-N% and grain yield to increasing amounts of fertiliser-N. Grain-N% for both winter and spring wheat increased, mostly linearly, throughout the range, whereas many of the grain yield curves reached a maximum and then declined with further additions of N. Provided curve sections exhibiting dilution effects were excluded, the linear or near-linear relationship between grain-N% and fertiliser-N allowed linear regression models to be fitted. This showed that, over a range of 50-175 kg N ha^?1, an average of 32 kg ha^?1 of fertiliser-N was required for an increase of 0.1% N in grain dry matter of winter wheat or 56 kg N ha^?1 for an increase of 1% protein. Results from 3 years of experiments conducted by the Agricultural Development and Advisory Service (ADAS) agreed closely with those obtained from Rothamsted. Using the linear relationship between grain-N% and fertiliser-N, curves were plotted of grain yield against grain-N, adjusted for comparable additions of fertiliser-N (75, 100, 125, 150 kg ha^?1). The curves tended to have sections with rising yield for small applications of N, to exhibit a maximum in a central zone and descending sections for large applications. There was no well-defined ?critical level’? of grain-N%, beyond which this and grain yield were inversely related.     

Evaluation of physical and chemical characteristics of newly evolved wheat cultivars

Evaluation of quality characteristics of wheat provides significant feedback to breeders for selection/evolution of the most suitable varieties. Seven advanced wheat cultivars and two commercial varieties were studied for 11 physicochemical characteristics. These cultivars showed significant differences for all parameters except ash content, which showed no significant variation. Test weight ranged between 75.6 kg hl^?1 (NRL‐2005) and 80.5 kg hl^?1 (NRL‐2017). Kernel weight and volume were highest (4.0 g and 3.2 ml) for NRL‐9822 and lowest (3.3 g and 2.6 ml) for NRL‐2005. Biological yield was highest (14 040 kg ha^?1) for NRL‐9822 and lowest (12 380 kg ha^?1) for Takbeer variety. Grain yield varied between 4717 kg ha^?1 (NRL‐01‐7) and 4042 kg ha^?1 (NRL‐9736), non‐grain biomass between 9708 and 8083 kg ha^?1, protein yield between 614.3 and 480.8 kg ha^?1 and harvest index between 34.8 and 30.8%. Moisture content ranged from 7.46 to 9.07%. Gluten and protein contents were highest (39.69 and 13.81%) in NRL‐9736 and lowest (29.78 and 12.70%) in NRL‐9822. Test weight was positively correlated with kernel weight and volume and negatively associated with moisture, protein and gluten contents. Protein and gluten contents had a negative association with kernel weight and volume. Gluten content had a highly positive correlation with protein content. Grain yield was positively correlated with biological yield. Protein yield had a positive relationship with biological and grain yields and a negative association with harvest index. Copyright © 2005 Society of Chemical Industry     

Interrelationship of nitrogen nutrition with maize (Zea mays) grain yield,nitrogen use efficiency and grain quality

Eight maize (Zea mays L) hybrids were grown under five N levels with or without the nitrification inhibitor, nitrapyrin (2-chloro-[6-trichloro-methyl] pyridine), to evaluate N interactions relative to yield performance, N use efficiency, grain protein concentration, and kernel texture. Results indicate that maize hybrids can be grouped into three categories based on grain yield: (1) low N-responsive types which reach their maximum yield with 134 kg ha^?1 of applied N; (2) intermediate types that respond to moderate N levels (134 to 201 kg N ha^?1); and (3) high N-responsive types that respond to higher levels of N (201 kg N ha^?1). High N-responsive types, in general, increased yield with nitrapyrin treatment at all levels of N. Crop N utilisation efficiency for high N-responsive hybrids decreased, but was static for low N-responsive hybrids as N fertiliser increased. In general, as the grain yield of a hybrid increased in response to N, the concentration of protein in the kernel increased; although grain yields and protein concentration are negatively correlated among hybrids. Increased kernel translucence, an indicator of kernel hardness induced by N fertiliser, correlated highly positive with zein proteins. Isoelectric focusing analysis showed that increases in zein were primarily due to a quantitative increase in α- and γ-zein polypeptides. This study indicates that hybrids are different in their N requirements for maximum yield. Low N conditions not only restrict grain yield but also affect kernel textural quality.     

Interacting effects of tillage method,nitrogen fertiliser and secondary drainage on winter wheat production on a calcareous clay soil

The response of winter wheat to nitrogen fertiliser within the range 0–200 kg ha^?1 in 40 kg increments applied either in April or in May in two consecutive seasons (1976–77 and 1977–78) was tested in a field experiment on a calcareous clay soil that was either direct-drilled, shallow tine cultivated (5–8 cm), or mouldboard ploughed (23 cm). These cultivation methods had been used on the same plots in the four preceding seasons (1973 to 1976) in a comparison of cultivation systems. A comparison was also made with direct-drilling on land that had been deep tine cultivated (17 cm) during the 1973–76 experiment. In the second season (1977–78) effects were examined of newly drawn mole drains, on land that had been direct-drilled or ploughed. In both seasons the effect of cultivation method on grain yield was small when nitrogen fertiliser was applied at 80–120 kg N ha^?1. Nitrogen top dressings in April gave heavier yields than the equivalent dressings in May, partly because of dry weather after the May applications in both years. There was no interaction between method of cultivation and amount of nitrogen applied in 1976–77, but a significant interaction was detected in 1977–78 which was probably associated with less nitrogen being available in the uncultivated soil during the winter and spring. The results show that the potential yield of direct-drilled crops may have been underestimated in some earlier comparisons of different methods of cultivation where small uniform top dressings of nitrogen were applied to each cultivation treatment. Mole drainage increased yield especially at low rates of nitrogen and after direct drilling, These results indicate that direct-drilled and ploughed land may differ in their drainage requirements.     

Effect of drought and irrigation on the fate of nitrogen applied to cut permanent grass swards in lysimeters: Leaching losses

Nitrogen losses were measured in water draining from cut permanent grass swards growing in monolith lysimeters containing clay loam (Salop series) or silt loam (Bromyard series) soils. The swards were cut at 6-week intervals during the summer and were fertilised with calcium nitrate at rates of 0 and 400 kg N ha^?1 in each of five successive years (1977–81); in the first year the fertiliser was labelled with ¹⁵N. Four differing rainfall regimes were imposed from spring to autumn in each year. Mean annual losses of nitrogen by leaching from unfertilised swards were 3.8 kg N ha^?1 with mean nitrate-N concentrations in the water of about 1 mg N litre^?1. In fertilised lysimeters where rainfall distribution was that of the long-term average the mean annual total nitrogen losses were 41 kg N ha^?1 in the Salop soil and 15 kg N ha^?1 for the Bromyard soil; mean nitrate-N concentrations were 11.6 mg N litre^?1 and 5.1 mg N litre^?1, respectively. Losses of nitrogen and nitrate concentrations were similar to these quantities when irrigation increased the rainfall total to 120% of average. Where a drought was imposed for 2 weeks before and after each cut, mean nitrate-N concentrations increased to 20.3 mg N litre^?1 on Salop soil and 13.1 mg N litre^?1 on Bromyard soils; total annual nitrogen losses were 74 kg N ha and 33 kg N ha^?1, respectively. The largest losses were recorded when the drought period extended for four weeks before each cut and mean nitrate-N concentrations increases to 28.8 mg N litre^?1 on Salop soil and 34 mg N litre^?1 on Bromyard soil, with total annual nitrogen losses of 104 kg N ha^?1 and 109 kg N ha^?1, respectively. Losses of nitrogen derived from the fertiliser labelled with ¹⁵N were 7.3–8.4% of that applied in the Salop soil (29–33 kg N ha^?1), with little effect by the differing rainfall distributions. On the Bromyard soil, losses were 3.7% (14 kg N ha^?1) of the applied fertiliser in lysimeters not subjected to droughts. When the period of the drought extended before and after each cut, losses were 8.2% (32 kg N ha^?1) and increased to 17.9% (70 kg N ha^?1) when the drought period occurred entirely before each cut. Fertiliser nitrogen contributed 48–69% of the total nitrogen in drainage water from both soils in the first year.