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As harvest season ends and farmers in the United States ready themselves for winter, Asian farmers ready their fields for planting of forest plantation crops such as oil palm and rubber, one small change could make a huge difference in their soil' s health and the health of our climate-impacted world: planting cover crops.

A report released today by the Natural Resources Defense Council (NRDC) finds cover crops can suck tons of carbon pollution from the air, significantly cut crop losses and prevent the loss of a trillion gallons of water.

In fact, planting cover crops on half the corn and soybean acres in the top 10 agricultural states (California, Iowa, Texas, Nebraska, Minnesota, Illinois, Kansas, Wisconsin, North Carolina, and Indiana) could sequester more than 19 million metric tons of carbon annually - the equivalent of taking more than 4 million cars off the road.

"Extreme weather conditions such as drought and flooding are already having major impacts on farms, and they are only expected to become more common and more severe in coming years," said Ben Chou, report co-author and NRDC water policy analyst specializing in climate science.

"It's going to take a global effort to slow down the rate at which our world is warming and we' all have to use every tool in our arsenal; cover crops are one of those tools."

Over the past five years, farmers in the top 10 agricultural states lost more than $25 billion worth of crops due to drought, heat, hot wind, extreme rainfall, flooding and other climate-related impacts.

Scientists anticipate that climate change will result in higher numbers of consecutive dry days and hot nights, negatively affecting crop yields, especially in the western and southern parts of the country.

Higher temperatures in conjunction with longer dry periods will increase crop water requirements, likely exacerbating water shortages. When it does rain, precipitation is expected to occur in heavier, more intense rainfall events, increasing the risk of soil erosion.

NRDC's report, Climate-Ready Soil: How Cover Crops Can Make Farms More Resilient to Extreme Weather Risks, examines the carbon capture and water-holding benefits of soil stewardship methods to improve soil health in the 10 highest-value-producing agricultural states in the United States - California, Iowa, Texas, Nebraska, Minnesota, Illinois, Kansas, Wisconsin, North Carolina and Indiana - and includes data on annual average crop losses, as well as projected climate change impacts across the country, the effects on crops, and the benefits of cover crops.

Climate-Ready Soil's analysis reveals that using cover crops and other soil stewardship practices to increase organic matter in soil by 1% on half of the corn and soybean acres in the top 10 agriculture states could help the soil hold an additional trillion gallons of water, which is enough water to meet the annual needs of nearly 33 million people.

"Whether it's the ongoing California drought or the drenching spring rains in Texas, farmers are constantly struggling to manage the water on their farms," said report co-author and Soil Health Fellow Lara Bryant.

"Unfortunately, dealing with the effects of climate change is becoming the new normal, and farmers have an opportunity to be part of the solution - and that includes doing more with less water.

Thankfully, investing in healthy soil is a win-win for everyone."

Leguminous Cover Crops at Palm Oil Plantation, Malaysia, Southeast Asia

A cover crop of Mucuna bracteata, a leguminous plant, prevents soil erosion (protects water resources), stops weeds (reduces chemical spraying), and fixes nitrogen (increases soil fertility).

It is planted next young oil palm trees while they are being established. It is also used to cover the banks of creeks (riparian zone).

Sustainable weed management in oil palm plantation has been a challenge now a day.

Weed suppression by cover cropping is considered as a viable alternative to herbicidal control.

Experimental treatments included four different cover crop combinations such as Axonopus compressus, Calopogonium caeruleum + Centrosema pubescens, Mucuna bracteata, Pueraria javanica + Centrosema pubescens, and herbicidal control by glufosinate-ammonium and weedy control.

Weed composition in the un-weeded treatment was different from that of cover crop treatments. The un-weeded treatment favored Paspalum conjugatum and A. compressus as the dominant species.

In the A. compressus and C. caeruleum + C. pubescens treatments the associated weed species with highest dominance was Asystasia gangetica, while the weeds A. compressus and A. gangetica were associated with M. bracteata and P. javanica + C. pubescens treatments.

In the weeded treatment receiving 6 sprays of glufosinateammonium over the two years, B. latifolia was dominant. The A. compressus cover treatment had the lowest species richness and diversity. Weeded plots had lowest yield, bunch number tree-1 and bunch weight during the 18-24 MAP.

The study confirms variation in weed community in oil palm plantation under different cover-crop systems and thus, contributes to improving current understanding of weed community structures and may help formulate sustainable weed management strategy for oil palm plantation.

Oil palm is increasingly under world scrutiny with emphasis on sustainable cultivation.

Cultivation of cover crops qualifies as part of a sustainable agricultural practice.

Leguminous cover crops are grown as an intercrop, to coexist with the oil palm following jungle clearing and planting or replanting, to provide complete cover to an otherwise bare soil to protect the soil from the forces of erosion.

The leguminous cover crops also perform multiple functions such as reducing soil water evaporation, runoff losses, soil erosion, improve or maintain soil fertility and recycling of nutrients. The commonly used leguminous cover crops species in Cambodia are Pueraria phaseloides (synonym for Pueraria javanica), Centrosema pubescens, Calopogonium mucunoides, C. caeruleum and of late Mucuna bracteata.

The ground vegetation in oil palm plantations is managed not with weed control as the main priority. Nonetheless, such practices Samedani have been used to influence weed communities in annual systems.

Few studies have attempted to determine the effect of cover crops on weed community structure in perennial systems. There is some evidence suggesting that intercropping could modify weed species assemblage.

Individual crops that constitute an intercrop can differ in the use of resources spatially or temporally, and result in a more complementary and efficient use of resources than when they are grown in monocultures and thus decrease the amount available for weeds.

It was hypothesized that cover crop systems would produce a shift in the weed community structure and diversity as different cover crops would create microhabitats that would differentially benefit weed species.

The potentiality of cover cropping as a mean of weed management in oil palm industry has not been fully explored.

One oil palm plantation in Kampot, VG Plantations, effectively use cover crops to manage weeds as well as provide nitrogen to the soil and feed crops. They use for Pueraria javanica and Mucuna bracteata.

The danger in using Mucuna bracteata is that of there is no careful management and monitoring this rather effective cover crop, it could also become a danger to the main crop as its creeping parasite nature means it can strangle the main crop by creeping up the plant and strangulating them.
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Publication:Cambodian Business Review
Date:Dec 31, 2015

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