Nitrogen was applied in single and split applications at rates of 0, 300, and 600 mg per pot (equivalent to 0, 50, and 100 pp2m) to rye grown in a growth chamber at 10 and 21 C. Low and high soil moisture levels were maintained by watering to field capacity when soil moisture reached 15 and 60% of field capacity. Responses to these variables were measured by forage yields, total N uptake, and percent N in the plants.
With either low temperature or low soil moisture, higher forage yields were obtained with single N applications. Only under both high temperature and high soil moisture was it advantageous to split N. With high soil moisture, split N improved yields in the second harvest. This would, in effect, extend the grazing period. Soil moisture was more limiting to growth in the first harvest, while temperature was more limiting in the second harvest.
When N was applied in a single application, plant uptake (rag N per pot) was usually greater than or equal to treatments with split apnlications.
Plant N content at 21 C was higher with single N applications but at 10 C was higher with split applications. Generally, low soil moisture increased N content of the forage compared with high soil moisture.
The variable responses to N obtained under different temperatures and soil moisture levels will aid in interpreting field results.