In 1970–71, five N‐rate field experiments were conducted with fall‐seeded soft red winter wheat (Triticum aestivum, L.) on limestone‐derived soils in Pennsylvania. Varieties ‘Blueboy’ and ‘Redcoat’ were compared at two locations. At three locations, only Blueboy was grown. Redcoat is widely grown in Pennsylvania, but Blueboy was only recently introduced. The relative nitrogen requirements of these varieties, therefore, was essentially unknown when these studies were begun. Fall and spring applications of 0, 34, 67, 101, 135, and 168 kg/ha of N as ammonium sulfate were compared at each location. The nitrogen content of grain plus straw associated with maximum attainable yield of dry matter was similar among locations and varieties, the mean percent N and its standard deviation being 1.38 ± 0.06%. Yields of grain invariably were depressed when nitrogen in grain plus straw exceeded the mean value of 1.22 ± 0.06% (S.D.). The latter value is considered to represent the internal N requirement of the wheat associated with optimum production of grain, and it corresponds to the percent N in grain plus straw associated with 95 to 98% of total dry matter production. Recovery of fertilizer N was significantly greater for spring than for fall applications, although differences were small (means were 56 and 48%, respectively, for all locations). Yields of Blueboy were substantially greater than those of Redcoat at locations where these varieties were compared. Interactions of rate and time of N application on yields of grain and dry matter and N yields were not significant. Total uptake of N required per unit of wheat grain for maximum attainable yield is almost twice that required for corn.

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The effects of N fertilization in the northeastern states on percent protein in soft winter wheat (Triticum aestivum L.) need to be evaluated in relation to time and rate of application and variety as a basis for developing practices that achieve the desired range in wheat protein. Fall and spring applications of different N rates to ‘Blueboy’ and ‘Redcoat’ varieties of soft winter wheat were compared at five locations on limestone‐derived Pennsylvania soils. Average protein contents were increased from 10.9!)% with no N applied to 14.3% with N fertilizer. The optimum rate of N for maximum grain yield often resulted in higher protein content than is considered desirable in grain used for pastry making. Under comparable conditions, the average protein contents of Redcoat and Blueboy wheats, respectively, were 13.3 and 11.8%. Spring application consistently gave higher protein contents than fall application, although the average difference was small (0.6%). Yields of protein were higher for Blueboy than for Redcoat, despite higher percent protein in the latter, because grain yields of Blueboy were substantially greater than yields of Redcoat. The importance of soil N as a source of N in these experiments was illustrated by the significant correlation that existed between relative N mineralization rates of soils from zero‐N plots and corresponding protein yields.

Corn seeds were germinated near bands of fertilizer containing urea, biuret, cyanuric acid, ammonium, and certain other materials in sand‐solution cultures varying in urea and biuret, in closed systems containing gaseous NH3, and in soils with varying amounts of exchangeable NH4. Seeds were also soaked, before germination, in solutions of urea, biuret, (NH4)2SO4, or NH4OH. Germination was greatly inhibited by gaseous NH3 in closed systems, by more than 32% NH4‐saturation of the soil, and by soaking seeds in NH4OH; seeds that did germinate produced normal plants. In the field, germination was not affected but seedlings were injured by 1.5 lb or more of biuret‐N per acre (38‐inch rows); up to 1.5 lb cyanuric acid per acre had no harmful effects. Seed injury by NH3 released from urea is dependent upon hydrolytic activity, soil aeration, rate of nitrification, exchange capacity, and volume of soil between fertilizer and seed. Germination is affected by NH3; biuret principally affects seedling development after germination.

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