The impact of mineral fertilizers on P intake and balance in winter and spring wheat was studied on experimental farm "Peterlauki" of the Faculty of Agriculture, Latvia University of Agriculture. The experiments were carried out on sod-pseudogley sandy clay loam soil in 1999-2001. Potassium fertilizer rate K90 was constant over the entire experiment, but phosphorus rates were as follows: P0, P60, P90 and P120 for winter wheat, and P0, P45, P60, P90 for spring wheat. Two different nitrogen levels N60 and N120 for winter wheat, and N60 and N90 for spring wheat were used. Meteorological conditions during the experimental years were quite different. The experiment showed that P content in the grain of winter wheat changed depending on fertilizer rate and meteorological conditions. More significant P changes were observed at a lower nitrogen rate (N60). Growing fertilizers rates for winter increased N utilization coefficient from 0.64 to 0.93 at N60K90, but at N120K90 - from 0.59 to 0.63. In spring wheat, growing P fertilizer rates increased N utilization coefficient from 0.52 to 0.56 at N60K60, but at N90K60 - from 0.47 to 0.49. All P fertilizer rates applied in winter wheat and spring wheat provided a positive total P balance.

The use of winter wheat (Triticum aestivum L.) as a dual-purpose forage and grain crop is important to the agricultural economies of the Southern Great Plains of the USA. Planting date is an important management factor in determining the economic success of a dual-purpose winter wheat enterprise. The overall objective of the research reported in this paper is to determine the economic optimal planting date for dual-purpose winter wheat production. The specific objectives are to determine wheat fall–winter forage yield, wheat grain yield, and wheat test weight response to planting date for dual-purpose winter wheat production. Field studies were conducted in north central Oklahoma from 1991–1992 through 1999–2000. The impact of alternative planting dates on dual-purpose wheat fall–winter forage yield, grain yield, and test weight was estimated. Estimated response functions illustrate that delaying the planting date from 10 to 30 September resulted in an 18% increase in expected grain yield, a 68% decrease in expected fall–winter forage yield, and only a 0.5% increase in expected test weight. Optimal planting date is sensitive to the relative value of wheat fall–winter forage and wheat grain, but not sensitive to wheat test weight discount schedules. When the value of wheat forage is high relative to the value of grain, it is more profitable to plant early to increase expected forage yield. Alternatively, when the value of grain is high relative to the value of forage, later planting generates greater net returns.

The influence of cold hardening on heat generation in winter wheat seedling shoots during cold stress is discussed. In seedling winter wheat shoots, the temperature of "living" plants was higher, than in the ones "killed" during short-term low-temperature stress (cold shock). The study of the influence of cold shock intensity has shown that an increase in cold shock intensity caused a larger temperature difference between "living" and "killed" seedling shoots and resulted from an increase in thermogenesis in winter wheat seedling shoots. Cold hardening reduced this temperature difference between "living" and "killed" winter wheat seedling shoots. Treatment of winter wheat shoots by an uncoupling agent (CCCP) caused both an increase in temperature and survival during cold shock.

A database was compiled from the results of field N effect experiments on winter wheat published in Hungary. A total of 65 winter wheat experiments were included in the evaluation. A medium correlation was found between the organic matter content of the soil in N control plots and the N effects on winter wheat. The organic matter (humus) contents in the experiments included in the database were determined using the method described by Tyurin (1937).

Durum wheat (Triticum durum Desf.) produced in the northern Great Plains and the Pacific Southwest of the United States is primarily of spring growth habit. The objective of this research was to determine the feasibility of winter durum production in Virginia, typically a soft red winter wheat (T. aestivum L.) production area. Adaptation and yield potential of 19 winter durum lines were evaluated at locations in different regions of Virginia: the northern piedmont plateau (1995–1998), the northern ridge and valley (1995–1998), the southern ridge and valley (1995–1998), and the northern coastal plain (1996–1998). Durum lines were planted in replicated trials along with soft red winter wheat in late September to early October and harvested in late June to early July, depending on location. Durum yields were highest and the yield advantage of soft red winter wheat lowest in the 1996–1997 growing season, which was drier than the 1995–1996 and 1997–1998 growing seasons. The highest yields and test weights of durum wheat were obtained at the northern piedmont plateau location. Winter durum lines from the Ukraine were best adapted to the Virginia climate. Winter durum yields averaged 30 to 40% less than soft red winter wheat. Test weights of most durum lines met the required minimum for grade U.S. no. 2 or better only in 1997. The results demonstrate that durum production in Virginia is possible, but inconsistencies in yield and test weight indicate that durum may be a relatively high-risk alternative to soft red winter wheat production.

A normalized quadratic input distance system is applied to estimate inverse demand relationships for wheat by class. Semi-nonparametric and Bayesian estimators are used to impose curvature on inputs and outputs. Price flexibilities are estimated for hard red winter, hard red spring, soft red wheat, soft white winter, and durum wheat. Durum wheat is found to be the most price flexible. Economically and statistically important differences in price formation across classes of wheat are found and are supportive of government programs differentiating wheat by class.

Rhizoctonia oryzae (teleomorph = Waitea circinata) causes sheath spot of rice and root rot of wheat and barley. R. oryzae commonly is isolated from barley, wheat, and pea plants in eastern Washington and Idaho. Eight representative isolates were tested for virulence on spring barley (Hordeum vulgare cv. Baronesse), soft white winter wheat (Triticum aestivum cv. Madsen), and hard red spring wheat (cv. Scarlet) planted in natural soil in the greenhouse and maintained at 16°C. All isolates caused significant reduction of emergence in barley, but only seven of the eight isolates and one of the eight isolates reduced emergence of winter wheat and spring wheat, respectively. All isolates caused significant stunting and reduction in the number of seminal roots, root length, and number of root tips on wheat and barley. Some isolates also reduced the frequency of fine secondary roots, resulting in a reduction of the average root diameter. Spring barley was more susceptible to R. oryzae than winter or spring wheat. The main effects of both cultivar and isolate were significant, and there was a significant isolate-cultivar interaction. R. oryzae isolate 80042 was the most virulent on barley, whereas R. oryzae isolate 801387 was the most virulent on wheat. The two isolates from pea were intermediate in virulence on wheat and barley. When screening germ plasm for potential resistance, isolates exhibiting the maximum virulence for each host should be used.

The split-plot design experiment, in four replications, investigated 2 variables: I - fertilization - postharvest residues and postharvest residues with straw, II - liming - 00.71.42.1 (CaO t/ha). The winter wheat cultivated after underploughed winter rape straw, as compared to that without straw, showed a lower number of overwintered plants, of grains per ear, grain weight per ear, grain yield, protein yield and crop energetic value. Liming did not compensate for the yield decrease caused by a negative effect of underploughed winter rape straw on winter wheat grain yield

The split-plot design experiment, in four replications, investigated 2 variables, I - fertilization - postharvest residues and postharvest residues with underploughed straw, II - ammonium nitrate - 0255075 (N kg/ha). The winter wheat cultivated after underploughed winter rape straw, as compared to that without straw, showed a lower number of overwintered plants, of grains per ear, grain weight per ear, grain yield, protein yield and crop energetic value. Nitrogen fertilization did not compensate fully for the yield decrease caused by a negative effect of underploughed winter rape straw on winter wheat grain yield