Seasonal Growth and Accumulation of Nitrogen, Phosphorus, and Potassium by Orchardgrass Irrigated with Municipal Waste Water

Abstract

AbstractA 2‐year field study was performed to determine the seasonal growth and nutrient accumulation of a forage grass receiving 7.5 cm/week of domestic primary‐treated waste water. The average N and P concentrations in the waste water were 31.5 and 6.1 mg/liter, respectively. An established sward of ‘Pennlate’ orchardgrass (Dactylis glomerata L.) was managed on an annual three‐cutting system. Grass samples were taken periodically during the growing season to determine plant dry matter accumulation and uptake of N, P, and K.Plants accumulated dry matter and P up to 31 days during the initial harvest period or between the early and late heading stages of growth. Plant accumulation of N and K also leveled off after 31 days in 1978, but continued to increase until the end of the period in 1979. Nutrient and dry matter accumulation increased up to 35–40 days growth during the second harvest period. During the third harvest period in 1979, plant growth was similar to the second harvest period; while in 1978 accumulation slowed after 15 days and then increased again after 29 days. Changes in nutrient uptake within a harvest period were related to both changes in dry matter accumulation and plant nutrient concentration. For maximum yields and nutrient removal, it is recommended that orchardgrass be initially harvested at the early heading stage of growth in the spring. Subsequent harvests should be performed at 5‐ to 6‐week intervals.Average daily dry matter, N, and P accumulation were highest during the first harvest period which occurred primarily during May in Hanover, New Hampshire. Therefore, this time would be the most appropriate to increase the application rate, thus utilizing the excess waste water which otherwise would have to be stored during the winter season.