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Archive | December, 2013

Synthetic Nitrogen Lingers for Decades

Runoff_of_soil_&_fertilizerNitrogen fertilizer applied to crops lingers in the soil and leaks out as nitrate for decades towards groundwater — “much longer than previously thought,” scientists in France and at the University of Calgary say in a study.

Thirty years after synthetic nitrogen (N) fertilizer had been applied to crops in 1982, about 15 percent of the fertilizer N still remained in soil organic matter, the scientists found.

After three decades, approximately 10 percent of the fertilizer N had seeped through the soil towards the groundwater and will continue to leak in low amounts for at least another 50 years.

The findings show that losses of fertilizer N toward the groundwater occur at low rates but over many decades, says Bernhard Mayer, U of C professor of geochemistry and head of the Applied Geochemistry Group.

That means it could take longer than previously thought to reduce nitrate contamination in groundwater, including in aquifers that supply drinking water in North America and elsewhere, he says.

“There’s a lot of fertilizer nitrogen that has accumulated in agricultural soils over the last few decades which will continue to leak as nitrate towards groundwater,” Mayer says.

Canada and the United States regulate the amount of nitrate allowed in drinking water. In the 1980s, surveys by the U.S. Environmental Protection Agency and the U.S. Geological Survey showed that nitrate contamination had probably impacted more public and domestic water supply wells in the United States than any other contaminant.

The study, “Long-term fate of nitrate fertilizer in agricultural soils,” was published in the Proceedings of the National Academy of Sciences.

This summary appears in the December 2013 issue of Acres U.S.A.

Vetch Cover Crop Recommended for Organic Zucchini

Illustration_Vicia_sativa0In a new study, the popular cover crop vetch (Vicia sativa L.) was used in a two-year field experiment designed to determine the effects on organic zucchini yield and quality of vetch residue management strategies incorporating green manure using a roller-crimper (RC) and organic fertilizers.

To allow for timely crop rotation in organic farming, the growing cycle of cover crops is often terminated before natural maturity using mechanical chopping and/or plowing, field disking, mowing or crushing with a roller-crimper. Innovative conservation tillage production systems using RC technology to end cover crops are gaining popularity. The technique uses one or two passes of the RC to flatten the cover crops, leaving a thick mulch layer into which the next crop is sown or transplanted. The thick mulch hinders the development of weeds during the critical growing period, contributes to reduced soil erosion and increases soil moisture and fertility.

Researchers used municipal solid waste compost, anaerobic digestate and a commercial organic fertilizer in the field experiments designed to determine yield, yield components, crop quality, and soil nutritional status in organic zucchini fields in southern Italy.

“Our results showed that zucchini yield was influenced positively by the vetch residue management strategy, although the response was significantly different between years,” the scientists said. “The vetch cover crop increased marketable zucchini yield in the first year by 46.6 percent compared with the fallow treatment, indicating that this fertility-building crop could reduce off-farm nitrogen (N) fertilizer input for subsequent crops. Averaging over two years of the experiment, marketable zucchini yield increased by 15.2 and 38 percent with the roller-crimper mulch and green manure plow-down, respectively, compared with the fallow treatment, although differences were significant only in the first year.”

The application of organic fertilizers in vetch management plots increased marketable zucchini yield by 21.8 percent in the first year compared with the unfertilized control.

This article appears in the December 2013 issue of Acres U.S.A.

High-Tunnel Strawberry Production

strawberry d3401-1At a time when Arkansas-grown summer strawberries are a happy memory, Elena Garcia and her team are just gearing up for their growing season. Garcia, a professor and extension fruit and nut specialist for the University of Arkansas System Division of Agriculture, is studying the use of high tunnels for winter and early spring strawberry harvest in Arkansas. Her research, which aims to extend the short, but sweet, strawberry growing season in Arkansas, is one of 18 nationwide to earn a grant as part of the National Strawberry Sustainability Initiative. Arkansas once ranked among the nation’s top strawberry growers, but California and Florida have taken over the majority of production. Total U.S. strawberry production was valued at $2.4 billion in 2011.

This article appears in the December 2013 issue of Acres U.S.A.