PS 19-18
Intercropping for on-farm grain production and environmental quality in dairy pasture systems
In New England, the production of annual grain crops can be accompanied by environmental tradeoffs in terms of soil and water quality, particularly during extreme weather events. Intercropping annual grain crops with perennial forage crops such as alfalfa may be an approach to reducing the environmental impacts of annual crop production but may also decrease annual grain yields. This field experiment evaluated alternative approaches to establishing feed corn within a mature alfalfa stand. Nine treatments were replicated four times in a randomized complete block design in summer 2013 at the University of New Hampshire Kingman Research Farm in Madbury, NH. The treatments included an alfalfa control (no corn), a conventional full-tillage control (no alfalfa), and seven intercropping treatments differing in alfalfa disturbance intensity. The intercropping treatments utilized a variety of approaches to establishing corn within the alfalfa stand including mowing, strip-tillage, undercutting, and herbicide (glyphosate) application. No additional fertilizers or herbicides were applied following corn planting. Response variables measured during the study included soil quality, grain yields, weed communities, and alfalfa stand persistence and recovery the following season.
Results/Conclusions
Corn grain yields differed across treatments (P < 0.0001) and were lowest in those where the alfalfa was flail mowed. These treatments also had high weed abundance and low corn leaf chlorophyll contents. In contrast, corn grain yields in several of the intercropping treatments that did not involve flail mowing (i.e., the strip-till and no-till treatments with a single pre-plant application of glyphosate) were comparable to the conventionally-tilled control. These results suggest that corn can be successfully intercropped with alfalfa with minimal or no tillage, as long as the alfalfa stand can be managed in a way that does not stimulate weed emergence from the soil seed bank. While flail mowing alfalfa prior to corn planting consistently resulted in high weed biomass and low corn yields relative to the control, several alternative methods appear to be viable options for balancing grain yield with longer-term pasture management and environmental quality goals.