Low Nitrogen Rates Research Articles

A survey of farmer practices and attitudes to nitrogen management in the northern New South Wales grains belt

Summary. The use of nitrogen fertilisers to arrest the decline in soil nitrogen fertility in the northern grains belt of New South Wales has been the subject of many years of research, however, little is known about how farmers make decisions about nitrogen fertiliser. A survey of 400 wheat farmers in northern New South Wales in April 1997 revealed that many have recently changed their fertiliser practices. Although most respondents had been growing wheat since the 1960s, regular applications of nitrogen only commenced in the mid 1980s. Initially only low rates of nitrogen were applied, but in the last 2–5 years, the nitrogen rates have substantially increased. These changes are notable because until this decade, most were content to rely mainly on mineralisation of soil organic nitrogen, whereas, now, half the respondents in the survey plan to add as much nitrogen in fertiliser in 1 year as was removed in the previous year’s wheat crop. Farmers were asked to rate the importance of a number of factors that have been promoted as means of tactically adjusting fertiliser rates. This study found a disparity between the level of measurement and precision suggested by the majority of research, development and extension programs compared with the methods used by farmers. In general, the respondents to the survey have rejected, or are yet to adopt, regular soil testing, the use of climate forecasts and decision support programs. Rather, they rely on simple rules of thumb based on readily accessible data such as past grain protein content and cropping history.

Nitrogen fertilization and aspects of fruit yield in a Missouri black walnut alley cropping practice

Increasing nut production through cultural practices is important to landowners for maximizing economic gain from agroforestry plantings. This project studied the effects of applying low rates of nitrogen (N) fertilizer during either the spring or late summer, on pistillate flowers formed, fruits retained, and fruit quality (percentage kernel) in black walnut (Juglans nigra L.) grown under alley cropping management. Treatments consisted of two forms of nitrogen fertilizers (NH4NO3 and NaNO3) applied in mid-April, or mid-August of 1995 and 1996, and a nonfertilized control group. Pistillate flowers counted in May, 1996, showed that fertilized trees, regardless of timing or form of N applied, produced from 2.3 to 3.4 times the number of pistillate flowers as unfertilized control trees. Through the season, the fertilized trees had greater fruit retention, and ended with 2.9 to 4.8 times more walnuts (on a whole tree basis) than nonfertilized control trees. In addition, all fertilizer treatments resulted in increased nut yields from 1995 to 1996, while unfertilized control tree yields decreased approximately 70%. Summer application of fertilizer showed the greatest benefit to kernel weight. Average kernel weights of nuts from the summer-fertilized trees increased from 1995 to 1996, while kernel weight averages from spring-fertilized and nonfertilized trees remained unchanged or decreased.

Influence of cropping system on sharp eyespot in winter wheat

Wheat was assessed for sharp eyespot in three field trials using factorial designs which investigated preceding crops and soil tillage effects (inversion vs non-inversion), soil structure (compacted vs non-compacted) and wheat management techniques (sowing date and density, nitrogen fertiliser rate and form, removal or burial of cereal straw). A previous host vs non-host crop increased sharp eyespot. The effect of soil tillage depended on crop succession: if the previous crop was a host, soil inversion vs non-inversion decreased disease by burying infectious host crop residues; if the previous crop was a non-host itself preceded by a host, soil inversion vs non-inversion increased disease by carrying infectious material back to the soil surface. Uncompacted vs compacted soil increased sharp eyespot, but only at early stages. Early sowing always increased disease. High plant density (giving rise to low tillering) increased early and decreased late disease levels. A high vs low nitrogen rate and a low vs high ammonium content of the fertiliser slightly increased sharp eyespot. Removal or burial of straw did not affect disease. A hierarchy of the factors was established: crop succession and soil tillage were dominant factors; among the wheat management practices, only sowing date and plant density had important effects.

Grain nitrogen content of winter bread wheat ( Triticum aestivum L.) as related to crop management and to the previous crop

Low-input management for wheat production (less fungicide, low nitrogen rate) could affect grain protein content. The impact of the previous crop could also be a determining factor for wheat quality. A long-term field experiment located near Toulouse (southwestern France), comparing different rotations and management schemes from 1984 to 1993, was used to assess the effect of N availability and diseases on grain nitrogen concentration (GNC) of wheat. GNC ranged from 1.6 to 2.8%, increasing with the input level in 5 years out of 10, as the result of higher nitrogen levels and crop protection with fungicides. Leaf brown rust, high temperatures and water shortage, which affected dry matter accumulation during grain filling, were responsible for high GNC. GNC was generally correlated with N uptake when nitrogen availability was the main limiting factor and to the nitrogen harvest index (NHI) when foliar diseases or drought limited grain production. N uptake in the absence of N fertiliser ranged from 20 to 200 kg ha −1 depending on the previous crop. GNC was closely related to the nitrogen nutrition index (NNI) at anthesis.

Influence of cropping system on foot rot of winter wheat in France

Wheat was assessed for foot rot and the responsible species ( Microdochium nivale, Fusarium spp.) identified at key stages on three different field trials: (a) the first comprised plots cultivated with cereals for a variable number of years after four years of non-cereals; (b) on the second, wheat was grown on compacted and uncompacted soil structure; (c) the third studied the effects of five wheat management techniques (sowing date and density, nitrogen fertilizer dose and form, removal/burial of cereal straw) on various sites. Microdochium nivale (which was predominant at early stages) and Fusarium spp. (which was predominant at later stages) were shown to behave very differently: the former was increased and the latter decreased where wheat was a previous crop, whereas foot rot as a whole was not affected by crop succession. Uncompacted vs compacted soil only increased foot rot at an early stage when M. nivale was predominant. Early sowing and high plant density (giving rise to low tillering) increased early foot rot and levels of M. nivale and decreased late foot rot and levels of Fusarium spp. A high vs low nitrogen rate and a low vs high ammonium content of the fertilizer increased foot rot; removal or burial of straw did not affect disease.

Effect of treated effluent irrigation and nitrogen on yield and nitrogen use efficiency of wheat

Yield and nitrogen use efficiency (NUE) of wheat was investigated under field conditions using two types of irrigation waters with and without nitrogen on a sandy-loam to loamy-sand soil during 1992–1993 and 1993–1994. Depending upon different nitrogen treatments, the mean crop yield ranges in 1992–1993 were: grain yield 6.19–6.87 Mg ha − and biomass 15.41–16.34 Mg ha −1 receiving treated effluent. The mean crop yield ranges in 1993–1994 were: grain yield 0.46–3.23 Mg ha −1 (well water) and 5.20–6.54 Mg ha −1 (treated effluent); and biomass 1.84–10.80 Mg ha −1 (well water), and 16.00–19.29 Mg ha −1 (treated effluent). The NUE for grain yield in 1992–1993 was between 16.70–50.23 kg kg −1 N (well water) and 20.65–91.56 kg kg −1 N (treated effluent). Whereas the NUE in 1993-94, varied between 10.49–32.13 kg grain kg −1 N (well water) and 21.30–72.93 kg grain kg −1 N (treated effluent). The NUE for total biomass in 1992–1993 varied between 46.54–130.32 kg kg −1 N (well water) and 53.66–158.77 kg kg −1 N (treated effluent). Similarly, the NUE in 1993–1994 varied between 35.99–102.1 kg biomass kg −1 N (well water) and 59.27–161.89 kg biomass kg −1 N (treated effluent). A significant decrease in NUE was observed with increasing nitrogen application both for grain and biomass production. In conclusion, a higher grain yield and NUE of wheat crop can be achieved with low application rates of nitrogen if the crop is irrigated with treated effluent containing nitrogen in the range of 20 mg L −1 and above.

Effects of Rice Quality on Profit-Maximizing Ratoon Crop Nitrogen Decisions

Optimal nitrogen rates for the ratoon crop are derived utilizing estimated production functions for rice grain quantity and quality. Field-level data for 464 ratoon rice-cropped fields representing more than 50,000 acres were collected in Texas during 1987 to 1989. Returns above variable costs (RAVCR) are calculated using both a non-quality-dependent rice price and a price based on grain quality factors. When considering quality, maximization of RAVCR requires lower nitrogen rates and realizes lower RAVCR per acre than are projected based on non-quality dependent prices. Results reinforce existing recommendations and cast doubt on decisions to exceed recommended rates.

Preconditioning effects of nitrogen relative addition rate and drought stress on container-grown lodgepole pine seedlings

Five-week-old Pinuscontorta var. latifolia Engelm. seedlings were subjected to 6 weeks of preconditioning with four combinations of watering and nitrogen fertilization, followed by a second 6-week period to evaluate the continuing effects of the preconditioning treatments. In both phases, the seedlings were fertilized with nitrogen at either 3 or 6%•d−1 relative addition rate and were either subjected to drought or well watered. Preconditioning treatments were crossed with second-phase treatments to give a 24 factorial design. Nitrogen and watering preconditioning effects on biomass, water relations, nutrients, and metabolic constituents persisted at least 6 weeks regardless of the second-phase treatments. Interaction between nitrogen and watering treatments applied simultaneously was found only in relative growth rate and foliar potassium concentration. Interactions between preconditioning and second-phase treatments were found in foliar nitrogen, potassium, and α-amino nitrogen concentrations, root water content, and xylem pressure potential. Foliar starch concentration increased when either nitrogen or water were limiting, but showed no evidence of interaction or preconditioning effect. Preconditioning at the lower nitrogen rate resulted in elevated reducing sugar concentration in the leaves, which persisted during the second-phase period. We did not detect an effect of increased reducing sugars on osmotic potential. Preconditioning at the lower nitrogen rate increased subsequent root weight ratio and reducing sugars concentration, which could contribute to drought resistance. Turgor regulation occurred via changes in cell wall elasticity rather than osmotic adjustment.

CROP ROTATION AND NITROGEN RATE INFLUENCE PROCESSING TOMATO QUALITY

A study was conducted from 1989 to 1991 to examine the effects of continuous tomato cropping, short-term crop rotation and, nitrogen fertilization rates on processing tomato quality. Research was conducted at two sites in southwestern Ontario, Leamington and Dresden, in split-plot experimental design. The rotations included tomato (Lycopersicon esculentum) - winter wheat (Triticum aestivum) (underseeded with red clover (Trifolium pratense), tomato-winter wheat-soybean (Glycine max), tomato-alfalfa (Medicago sativa), and tomato-rye (Secale cereale). Nitrogen fertilization rates of 0, 45, 90 and 135 kg/ha were used. Processing tomato cv. Heniz 9230 and Nabisco Brands Ltd. 7107 were assessed for colour, % soluble solids and total solids, and blossom end rot [BER]. In most instances, continuous tomato [C-T] had significantly poorer colour, soluble solids, and total solids than fruit from the various crop rotations. High nitrogen rates for C-T at Leamington, resulted in improved soluble solids and total solids, but had no significant effect on colour. A lower incidence of BER consistently occurred with low rates of nitrogen. Our results indicate that short-term crop rotation and nitrogen management in processing tomatoes can enhance fruit quality when compared to C-T.

ALTERNATIVE APPROACHES TO SOIL EROSION, FERTILITY, AND PEST MANAGEMENT OF CABBAGE

Raised beds (0.9 m wide, 1.8 m centers, 6.1 m long) were formed in Oct. 1988. Beds were either left bare or seeded with rye (Secale cereale) or hairy vetch (Vicia villosa). Plots were sprayed with glyphosate in April, 1989. Rye was completely killed, but hairy vetch was not. Bed height was maintained best with beds covered with rye. In a 3 by 4 factorial, four rates of nitrogen (45, 90, 134, and 179 kg/ha) were applied to each soil cover treatment. On April 17, cabbage (Brassica oleracea cv. Solid Blue 760) was transplanted two rows per bed, with 30 cm spacing in rows and between rows. There was no mowing or cultivating prior to transplanting. A linear increase in yield was observed with increasing applications of nitrogen. The cabbage yield was less in rye than in vetch orbare soil. The yield difference between rye and bare soil was more pronounced at the low rates of nitrogen than at the high rates of nitrogen. Cabbage grown in rye had significantly fewer aphids, thrips, and cabbage loopers than did cabbage grown in bare soil.

A comparison of the effects of liquid manure (urine and water) and nitrogen fertilizers applied to a grass-clover sward on soils of different pH value

SummaryIn a 3-year plot experiment on a perennial ryegrass plus white clover sward the pH of the soil on the main plots was adjusted to, and maintained as nearly as possible at, target levels of 5·25, 6·00 and 6·75 by applying either sulphur or lime. Within the main plots the effects on herbage yield, clover content and crude-protein content of applying four fertilizers were compared at nitrogen rates of 225 and 450 kg/ha annually. The fertilizers were liquid manure (urine plus water), prilled urea, a urea solution and an ammonium-nitrate fertilizer. The applications of the urea and the ammonium-nitrate fertilizers were accompanied by dressings of a potassium fertilizer which supplied the same weights of potassium as in the liquid manure. On average the smallest yields of dry matter and crude protein were associated with the lowest soil pH with no significant interactions between pH and fertilizer treatment. The liquid manure gave slightly smaller total yields of mixed herbage dry matter than the other fertilizers, particularly at the low nitrogen rate. The herbage from the liquid manure treatment had a higher clover content and produced a greater total yield of clover dry matter. The effects of the liquid manure on the clover agree with those noted in previous experiments, but no evidence was found that these effects resulted from the liquid manure increasing the pH of the soil and improving the conditions for clover growth. Similarly, no proof was obtained that the clover effects were due to the nitrogen in the liquid manure being wholly in the ammonium form. However, the value of liquid manure as a fertilizer for grassland was demonstrated clearly.

Soyabeans as Green Manure in a Maize Intercropping System

SUMMARYTwo experiments were conducted over a two year period at the International Rice Research Institute (IRRI) in the Philippines to evaluate the effect of a soyabean green manure intercrop on the grain yield of maize. Three rows of soyabeans were interplanted at 50 cm spacing between maize rows 1.5 m apart. Forty two days after planting the two outside soyabean rows were ploughed into the maize rows in a traditional ‘hilling up’ operation. At the zero and lower nitrogen rates, the soyabean green manure resulted in significantly larger maize yields than when maize was grown without green manure, providing the equivalent of 28 kg N ha−1 on the zero nitrogen plots. A response to green manure was also seen at 25 and 50 kg N ha−1. Allowing the central soyabean row to grow to maturity provided additional yield and protein.

A comparison of the yield responses of four grasses to a wide range of nitrogen application rates

SUMMARYThe yield results are reported for an experiment in which 21 rates of nitrogen fertilizer were applied on pure-sown swards of four grasses, S. 24 and Barvestra perennial ryegrass, S. 37 cocksfoot and S. 53 meadow fescue. Growth curves fitted to the herbage yield data for each grass in each year are presented. On average the total dry-matter yield curves for the two ryegrasses were similar to one another, but showed a slightly smaller response to nitrogen rates below 300 kg/ha than did S. 23 ryegrass in an earlier experiment, and a more rapid decrease in response at higher rates. S. 37 cocksfoot had a similar dry-matter yield response to the ryegrasses at the low nitrogen rates, but the response decreased more rapidly at nitrogen rates over 250 kg/ha. The dry-matter yield response of S. 53 fescue decreased even more rapidly with nitrogen rates over 200 kg/ha. The mean estimates of the optimal nitrogen rate for each of the four grasses, i.e. the nitrogen rate at which the dry-matter response had decreased to 10 kg/kg N, was 380, 372, 357 and 327 kg N/ha for S. 24, Barvestra, S. 37 and S. 53 respectively, compared with 409 kg/ha for S. 23 ryegrass in the earlier experiment.

Alleu cropping sequentially cropped maize and cowpea with Leucaena on a sandy soil in Southern Nigeria

The potential of alley cropping maize and cowpea with the giant Leucaena (Leucaena leucocephala (Lam) de Wit) cultivar K-28 was studied on an Entisol (Psammentic Ustorthent) in Southern Nigeria. In this trial the crops were grown in 4 m wide alleys formed by periodically pruned leucaena hedgerows. The effect of application of leucaena prunings, nitrogen fertilizer and tillage was studied. Despite the very intensive pruning regime (five prunings/year) for a six-year period, the leucaena hedgerows continue to produce substantial amounts of prunings, nitrogen yield and stakes. Application of nitrogen to the maize crop increased dry matter and nitrogen yield from the leucaena prunings. Although high nitrogen yield was obtained from the prunings, the application of low nitrogen rates was still needed for obtaining a high maize yield. Maize grain yield can be sustained at about 2.0 t/ha with continuous application of leucacna prunings only. Without application of leucaena prunings and nitrogen maize yield continued to decline with subsequent croppings. Cowpea grain yield was not affected either by leucaena prunings or by residual nitrogen. Tillage (rototilling) resulted in either higher or the same maize and cowpea yields as compared with no-tillage. Application of leucaena prunings resulted in higher soil moisture retention, organic matter, exchangeable K, Ca, Mg, and also nitrate levels in the soil solution. Leucaena and maize appear to extract soil moisture from different zones in the soil. Timely pruning of hedgerows is necessary to minimize shading.

Sulfur-coated urea as a source of nitrogen for cereals in Western Australia

The effects of four grades of sulfurcoated urea (SCU1, 35.1% nitrogen (N) and dissolution rate in water at 38�C of 10.5%; SCU2, 36.3%N and 25.9% dissolution rate; SCU3, 36.2%N and 1 1.2% dissolution rate; SCU4, 36.8%N and 15.4% dissolution rate) were compared with those of uncoated urea as sources of nitrogen for cereals in nine field experiments in two years. In five experiments at five sites in 1978, and in two experiments at two sites in 1979, comparisons were made between fertilizers topdressed either after sowing (1978) or before sowing (1979). In two further experiments in 1979, comparisons were made between fertilizers banded with the seed or topdressed immediately before or after sowing. Supplementary data on the effect of banding were obtained from a glasshouse experiment. There were no differences between sources in three of the five 1978 experiments. At the other two sites urea was superior to SCU when 50 kg N/ha was applied 2 weeks after sowing. Applications of urea 4 or 6 weeks after sowing gave grain yields, at these sites, up to 69 and 57% higher, respectively, than earlier applications. Apparent recovery of fertilizer nitrogen in one experiment in which it was measured was greater for two SCUs (13.1 and 2l.6%, respectively) than for urea (6+9%), but this was true only for applications at sowing. Urea applied 4 and 6 weeks after sowing resulted in much higher recoveries of fertilizer nitrogen (33.9 and 49.3%, respectively) and was more effective in overcoming leaching losses than was the slow-release SCU. There were no effects of time of application before sowing in the two 1979 experiments, indicating little or no loss of ammonia through volatilization, which precluded a comparison of the effects of the three nitrogen sources used. However, uncoated urea outyielded two SCUs in these experiments, by 7.5 and 6.5% in the first experiment and 5 and 2% in the second, respectively. When uncoated urea was banded with the seed at the equivalent of 70 or 140 kg N/ha all plants in the glasshouse experiment died. SCU at the lower nitrogen rate did not affect wheat emergence or survival but a 30% reduction in plant numbers resulted at the higher rate of SCU2. In one field experiment, uncoated urea reduced plant numbers by 96% compared with 20 and 13% for SCU3 and SCU4, respectively, when applied at 75 kg N/ha. Overall, this study showed no reason to use these grades of SCU in preference to uncoated urea, except where there is a need to band urea-containing fertilizer with the seed.

Rhizobium japonicum, nitrogen and phosphorus effects on nodulation, symbiotic nitrogen fixation and yield of soybean (Glycine max (L.) Merrill) in the Southern Savanna of Ghana

Abstract An experiment conducted in 1976 on a Nyigbenya-Hatcho soil tested the effects of Rhizobium japonicum inoculation, nitrogen and phosphorus on nodulation, symbiotic nitrogen fixation and yield of soybean (Glycine max (L.) Merrill) in the southern savanna region of Ghana. The treatments significantly increased plant height, node number per plant, pod number per plant, leaf area index, total dry matter per plant, grain yield and seed weight. Low rates of nitrogen and medium to high rates of phosphorus promoted nodule number, dry weight and leghaemoglobin content. Rhizobia inoculation and applied nitrogen increased protein in seed while the application of phosphorus was beneficial to oil formation. The data indicate that inoculation with Rhizobium japonicum could increase soybean yield on the Nyigbenya-Hatcho soil. Contrary to our expectation, rhizobia and nitrogen or phosphorus application did not cause further yield increases.

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

AbstractThe 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 NITROGEN SUPPLY ON THE SEED SET OF SPRING WHEAT AND BARLEY

Applications of NO3-N increased seed set of wheat grown under hot, moist conditions. An attempt was made to determine whether this improvement in seed set was due to improvement in plant nutrition or to NO3 poising the soil Eh above that at which phytotoxic ethylene is produced. Two pot experiments were carried out in a controlled environment chamber at diurnal temperatures 27/12 °C and slightly above field capacity. NO3-N or NH4-N with N-Serve ® were applied to Manitou wheat at rates of 45, 90, 135, and 180 kg N/ha in the first experiment, and to Manitou wheat and Conquest barley at rates of 23, 45, 90, 180 and 360 kg N/ha in the second. N-Serve successfully maintained the nitrogen in the NH4 form throughout the experiment. In both experiments, the seed set of the primary and secondary florets of wheat was directly proportional to the NO3-N rate. Wheat plants fed NH4-N exhibited significantly higher seed set than the NO3-N-fed plants at the low nitrogen rates. Seed set of lateral spikelets of barley was unaffected by rate, but the NH4-N-fed plants tended to produce slightly higher seed set. Ethylene was not detected in any of the soils. Since NH4-N corrected the seed set problem even at low levels of nitrogen, it was concluded that poor nitrogen nutrition and not the production of soil ethylene was responsible for poor seed set of wheat.

The Utilization of Endosperm Reserves During Early Growth of Barley Cultivars and the Effect of Time of Application of Nitrogen

The cultivars Akka and Hiproly with high grain nitrogen and Julia and Foma with low grain nitrogen and Proctor containing high or low nitrogen were compared. The high nitrogen forms germinated more rapidly and by day 6 had a higher axis dry weight than the low nitrogen types. By day 6 dry weight of tops and roots was similar in the high nitrogen cultivars but that of the tops was less in the low nitrogen forms. Analyses of the partition of nitrogen from endosperm to axes confirmed that for all types this was maximal after 48 h from planting and occurred at a similar relative rate so that 50 per cent of the endosperm nitrogen was translocated by 84-96 h from planting. Loss of endosperm dry weight was much slower and here high nitrogen forms translocated dry matter at a significantly faster relative rate than the low nitrogen types. Nitrate supplied at planting or on day 2 increased the rate of endosperm depletion in the low nitrogen types and resulted in their achieving similar axis dry weights to high nitrogen forms which were largely unaffected by nitrate supply. Delay in nitrate application had progressively less effect on endosperm breakdown. There was a greater uptake of nitrate by the low nitrogen forms and rate of uptake was rapid. Uptake of nitrate by high nitrogen types was initially rapid but was followed by a much slower phase. The results indicate that endogenous and exogenous sources of nitrogen are equally suitable for seedling growth. The significance of grain nitrogen content in relation to endosperm breakdown is discussed as is the strategy of partition of endosperm reserves between root and shoot.

Comparison of four wheat cultivars for yield and protein response to nitrogen fertilizer

Four wheat cultivars were compared for grain yield and grain protein response to nitrogen fertilizer at rates up to 135 and 336 kg N ha-1, in two field experiments, All varieties showed large responses to nitrogen in both years. The Mexican semi-dwarf WW15 and its white-grain derivative, Condor, yielded more than the standard cultivars Timgalen or Gatcher. Semi dwarf cultivars were found to respond significantly more to nitrogen than either Timgalen or Gatcher in the first year of these trials. Protein percentage of the grain was depressed by low rates of nitrogen in one year but increassd at higher rates. Gatcher and Condor had similar protein percentages; WW15 had the lowest and Timgalen the highest. Only Timgalen with high nitrogen reached a protein level for premium payment in the first year. In the second, all cultivars when fertilized qualified for similar premium payments per unit of land area. A simplified economic analysis showed that it was more profitable to grow and to fertilize the higher-yielding cultivars.