Submitted to: Grass and Forage Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/2/2002
Publication Date: N/A
Interpretive Summary: Most dairy farms in the Northeast use both fertilizer and animal manures to fertilize grass hayfields. We conducted a study for six years in Maine that compared four nutrient strategies (no fertilization, N fertilizer alone, NPK fertilizer, and liquid dairy manure), assessing the effects of these treatments not only on forage yield, but also on forage species composition, forage nutrient concentration and removal, and soil nutrient levels. Productivity was increased by up to 50% by making regular applications of either fertilizer or manure nutrients. We also found that forage nutrient concentration, especially for forage K, could be manipulated using different fertility regimes; regular application of K increased forage K concentration, and regular application of N fertilizer alone reduced forage K concentration. Forage P concentration was much more econsistent across nutrient treatments, but was lower where N fertilizer wa used alone. Crop removal of N, P, and K was influenced by differences in both forage nutrient concentration and forage yield. The balance between P and K input and removal shows that soil nutrient pools can supply P and K for an extended period. Phosphorus application from fertilizer or manure exceeded crop removal, while K application (N fertilizer and manure) approximately equaled crop removal for most of the experiment, due to the ability of the plant to continue to take up K beyond that needed for optimal yield. This research confirms that both fertilizer and manure nutrients can be efficiently used in forage production, and demonstrates the potential of these crops to cycle large amounts of N, P, and K.
Technical Abstract: Many long-term forage stands are not managed to their full potential, and their role in recycling on-farm nutrients is often overlooked. This 6-yr study was conducted to determine the capacity of a long-term, mixed-species hayfield in Maine, USA, to respond to commercial fertilizers and liquid dairy manure, including the effects on forage species composition and soil nutrient levels. The experiment was initiated in Stillwater, Maine, USA, in 1995, on a Lamoine silt loam soil. Nutrient treatments included N fertilizer, NPK fertilizer, liquid dairy manure (LDM), and an unamended control. Application rates of plant available N, P, and K were constant across treatments. Application of nutrients in any form increased forage yield, generally by 2-4 Mg ha-1 yr-1. Yield from NPK fertilizer was 5-25% higher than from LDM, a significant increase in three of six production years. Lower yields from LDM are attributed to N loss via volatilization. The forage sward became increasingly dominated by grass species as the experiment progressed. Forage N concentration increased by 2-4 g kg-1 when N was applied, regardless of N source (fertilizer or LDM). Forage P and K concentration was influenced by the application of each, and also by N application. Application of P and K increased soil nutrient level, and application of N decreased soil P and K, compared to the control. Forage nutrient removal accounted for all applied N and K, and nearly all applied P throughout the study period. This research confirms that both fertilizer and manure nutrients can be efficiently used in forage production, and demonstrates the potential of these crops to cycle large amounts of N, P, and K.