According to research, new strategies are needed to limit nitrogen and phosphorus losses from crop fields
Dairy farmers in the Northeast, Pennsylvania, US — facing a warming climate that exacerbates nutrient pollution but lengthens the growing season — can reduce the environmental impact of their operations and maximise revenues by double cropping and injecting manure into the soil, rather than broadcasting it, according to research.
A team of researchers, led by Penn State agroecologists, whose new study evaluated whole-farm production and the environmental and economic impacts of adopting these practises on a representative dairy farm in central Pennsylvania under recent historical and projected mid-century climate.
The research is important, according to Heather Karsten, associate professor of crop production/ecology in the College of Agricultural Sciences, because dairy farms — especially in the Northeast — are increasingly subject to more stringent regulations to reduce nutrient losses. With expected warmer conditions that will result in increased ammonia volatilisation from manure and more frequent and more severe storms that will cause more soluble phosphorus runoff, new strategies are needed to limit nitrogen and phosphorus losses from crop fields.
Double cropping offers the added benefit of keeping soil continuously covered by vegetation, reducing nutrient runoff, erosion and sedimentation. Winter small grains are seeded after corn for silage is harvested in September, and they germinate and grow until cold temperatures make them go dormant for the winter. They begin to grow again in late March and continue to develop until they are harvested in May, just before the corn crop is planted.
The researchers found that double-cropping increased and stabilised the farm’s feed production by providing forage from a winter rye crop with less dependency on the summer crops of corn silage and perennial cool-season grasses. Summer crops are susceptible to summer droughts, Karsten explained, which are expected to increase in this region due to warmer temperatures and increased evapotranspiration.
