Preliminary studies showed that winter wheat (Triticum aestivum L.) was losing relatively large amounts of N during the grain formation growth period. In order to further document this N loss, winter wheat plants were sampled at different times and at different locations before and after anthesis until maturity. The objective was to determine the nature and extent of dry matter and N losses that occur during the later stages of wheat development as influenced by N fertilization. While N is translocated rapidly from other plant parts to the grain after anthesis, total N losses ranged from 25 to 80 kg ha−1 in different experiments. These losses occurred during the grain filling period after anthesis. Dry matter and N losses were attributed primarily to the stems where 83 to 87% of dry matter losses occurred and 73 to 75% of the N. Dry matter and N losses from leaves and roots were relatively small. The N losses increased with increasing rates of N application. Plant N losses could account for much of the N losses found in soil N balance studies and certainly influence calculations involving fertilizer N efficiency. Grain protein could be doubled if plant N losses could be translocated instead into the grain.

Research monitoring N uptake by various agricultural crops has shown total N accumulations in the plant to increase prior to the growth stages around heading to flowering with a subsequent decrease in total N occurring after flowering. Volatilization of N from the plant may account for much of this loss as well as account for some of the deficits exhibited in N balance studies. Experiments were conducted in a gas‐tight growth chamber to determine what role plants alone may play in the overall loss of N from the soil‐plant system. Winter wheat (Triticum aestivum L.) was established, vernalized, and grown to maturity in the growth chamber. At first internode elongation, the chamber was closed and sealed for the duration of the experiment. Air supplied to the chamber during this period was bubbled through 1 N H2SO4 to remove ambient NH3 and through a reagent specific to NO and NO2 to remove these gases. Air samples were continuously drawn from the chamber and bubbled through 0.2 N H2SO4 to trap evolved NH3. These samples were collected weekly and analyzed using steam distillation. A second portion of the air sample was washed through the NO‐NO2 specific reagent and analyzed colorimetrically. Only trace amounts of NO and NO2 could be found at any time during the experiment leading to the conclusion that volatilization of these gases does not contribute significantly to the loss of N from the plant. Ammonia volatilized from the system at the rate of 0.34 to 0.89 ✕ 10−1 mg NH3‐N/m2/day prior to flowering. After flowering the rate of NH3‐N evolution increased to 1.03 to 1.32 ✕ 10−1 mg/m2/day. This dramatic increase in the rate of NH3‐N evolution at flowering coincides with the plant growth stage that researchers have begun to observe deficits in total N accumulations in the above ground portion of the plants. This data supports the hypothesis forwarded here, that volatilization of NH3 from plant tissue can partially account for the deficits in total N accumulation observed in plant tissue following flowering.

Consumptive use of water by alfalfa grown under two phosphorus fertility levels was measured in a 3‐year study at the University of Nebraska Scotts Bluff Station, located in western Nebraska. Soil moisture to a depth of 230 cm was measured with a neutron moisture meter at the start of the growing season, after each cutting, and after the last harvest. Irrigation water was delivered to the benches through an underground pipe and measured before flood irrigation. Alfalfa used 11.4 cm water per metric ton (4.95 in/T) of 88% dry matter hay. Alfalfa used water more efficiently in early May and June than July and August. Average water use per day was 4.1 mm (0.16 in) for the first harvest, 5.6 mm (0.22 in) for the second harvest, and 5.9 mm (0.23 in) for the third harvest. Average evapotranspiration ratios for the 3‐year period were 540 for the first cuttings, 630 for the second cuttings, and 860 for the third cuttings. The average evapotranspiration ratio for the three harvests over the 3‐year period was 680. Two levels of phosphorus applied to the soil did not alter water use nor total yields of hay.

Tie‐up of water‐soluble P is very rapid in calcareous soils. To determine the residual effect of high rates of applied P several experiments were established on soils ranging from 0.1 to 16.5% calcium carbonate equivalents (CCE). At each location an experiment was established with four rates of P (25, 50, 100, and 500 kg/ha). The soils were sampled annually for periods of up to 5 years. These soil samples were fractionated to determine the concentration of P in the various inorganic P fractions, using the techniques of Syers et al. (1972), as affected by rate of P application and time after application.Over time there was a decrease in the more soluble, plant‐available fractions indicating a shift of P from extractable to nonextractable forms. Also the various P fractions were correlated with two of the more commonly used soil methods, Bray and Kurtz no. 1 and the Olsen NaHCO3. As the CCE of the soils increased the correlation of the Bray and Kurtz no. 1 method with the fractions considered most available to plants decreased while the correlation of the Olsen method remained high.

The availability of residual N in the root zone greatly influences the amount of N fertilizer required to optimize winter wheat (Triticum aestivum L.) yields. In order to determine the availability of N at different depths in the root zone, and N placement study was conducted in the field on two soils in western Nebraska, a deep alluvial fine sandy loam (Entic Haplustoll) and a loess‐derived silt loam (Typic Arguistoll). Ammonium nitrate was placed on the soil surface and at depths of 30, 60, 90, 120, and 150 cm. Wheat plants were harvested six times during the spring growing season to determine N uptake. Soil moisture was at field capacity in the spring when experiments were established. While N uptake tended to decrease as the depth of N application increased, total dry matter production was not affected by depth of N placement. Wheat plants easily obtained N placed at depths up to 150 cm. The results indicate winter wheat roots are mostly established during the fall growing season and are in a position to provide N early in the spring for rapid above ground growth.