Strengthening legumes to tackle fertilizer pollution

e! Science News reports on research which shows that by boosting the nitrogen-fixing capacity of leguminous crops such as peas and beans, the environmental impacts of using artificial nitrogen fertilisers can be reduced.

 

Legumes use iron in the soil to carry out a complex chemical process called nitrogen fixation, which collects atmospheric nitrogen and converts it into organic forms that help the plant grow. When the plant dies, the excess nitrogen is released back into to the soil to help the next crop.

But often legumes are grown in areas with iron-depleted soil, which limits their nitrogen fixation. That's where research can lend a hand. The research team has created the world's first model for how iron is transported in the plant's root nodule to trigger nitrogen fixation. This is the first step in modifying the plants to maximize iron use.

"The long-term goal is to help sustainable agriculture practices and further diminish the environmental damage from overuse of nitrogen fertilizers," said Manuel Gonzalez-Guerrero, lead author of the paper from the Technical University of Madrid (UPM). "This can be done by maximizing the delivery of essential metal oligonutrients to nitrogen-fixing rhizobia."

Read more here.

Deep, permeable soils buffer impacts of crop fertilizer on Amazon streams, MBL study finds

Science Codex reports on research carried out in the Southern Amazon showing that some of the damaging impacts of agriculture on fresh water may be buffered by the very deep and highly permeable soils that characterize large areas of the expanding cropland.

The researchers looked specifically at the impacts of soybean agriculture on water quality and quantity at Tanguro Ranch, a 200,000-acre farm similar in climate and geography to large tracts of the Amazon where soybean production, largely for export as animal feed, is expanding rapidly. The ranch has watersheds that are entirely forested, as well as watersheds that are now entirely soybean cropland, allowing for a comparison.

"We were surprised to find that, despite intensive agriculture at Tanguro Ranch, the streams do not appear to be receiving a significant amount of either nitrogen or phosphorus, despite a high application of phosphorus fertilizer to adjacent cropland," says lead researcher Christopher Neill, director of the Ecosystems Center at the Marine Biological Laboratory (MBL).

This is in contrast to many Northern Hemisphere cropland areas where fertilizers are known to add nutrients to the soil that, with rainfall, run off into freshwater streams and rivers, leading to over-fertilization and low-oxygen conditions that endanger fish and other aquatic life.

At Tanguro Ranch, however, "the soils are old and highly weathered, very deep, and likely to be fairly uniform over great depths," Neill says. "Water infiltrates the soil very rapidly, and the soil has a great capacity to absorb the nutrients. It appears to act as an enormous buffer."

Read more here.

 

Beneficial exception to no-till rule

A strategic, one-off cultivation may be a viable option for no-till farmers battling to control herbicide-resistant weeds yet retain the long-term benefits no-till farming has brought them.

So says Queensland Country Life, reporting on a three–year research project in the state which has been set up to gauge the impact of a single tillage operation on no-till systems and determine the best timing of such an operation.

Queensland Department of Science, Information Technology, Innovation and Art senior soil scientist Dr Yash Dang, Toowoomba, said the growing incidence of herbicide-resistant, hard-to-kill weeds was one of the biggest threats to no-till farming systems.

“Many weeds have developed resistance to many herbicides,” he said. “With the narrow range of herbicide groups we have, they have developed herbicide resistance and farmers are finding it very difficult to manage.

Trials held in the first stage of the project last year showed that a one-time tillage with chisel or offset disc in long-term no-till helped control winter weeds and slightly improved grain yields and profitability while retaining many of the soil quality benefits of no-till.

Read more here.

 

Unearthing the Value of Soil

The UK version of the Huffington Post carries a fascinating feature on the importance of healthy soils to help us cope with climate, food and biodiversity challenges.

Soil is the most diverse ecosystem on the planet. Just one teaspoon contains as many as one billion bacteria, which provide vital services to support the growth of plant species and the myriad creatures who feed on them. Without healthy soil, everything from human health and food security to the resilience and biodiversity of the planet is at risk. The earth beneath our feet is so important that geomorphologist David R. Montgomery, author of Dirt: The Erosion of Civilizations, regards its quality and abundance as a measure of whether societies flourish or flounder. In the past, those with poor quality earth typically faced the prospect of dwindling in power or moving on to better lands.

"In today's world we're running out of places to move on to", says Montgomery. "The only option is to develop resilient soils."

The article describes the conventional approach to maximising returns from soils depleted by modern food production has been to turn to outside inputs, like greater amounts of fertiliser and irrigation, to induce crops to grow against the odds. These strategies may increase production and profits in the short term, but, says soil scientist Rattan Lal of Ohio State University, any effective solution requires a long-term perspective.

Lal maintains that it's not only possible to restore our "abused and taken-for-granted" soils - but that efforts to conserve and revive the earth benefit far more than just our own food chain. Healthy soils also deliver a range of essential ecosystem services, high among them being the absorption of atmospheric carbon dioxide. When it comes to strategies for solving the complex equation of climate change mitigation, biodiversity preservation, and safeguarding human security, soil conservation and restoration are "low-hanging fruit", says Lal.

Read the feature article here.

Winter crops protect, improve soil

Galesburg.com reports on how a growing number of farmers in Illinois are growing cover crops to improve their soils.

The reports says that the concept seems one of the hottest topics in the agriculture industry, said Russ Higgins, commercial agriculture educator with University of Illinois Extension and a representative of the Midwest Cover Crops Council.

Cover crops, such as radishes and ryegrass, are a secondary crop planted in the fall to protect and improve soil conditions during the period of time when crops normally wouldn’t grow, he said. Illinois farm fields, unless planted to harvestable crops like winter wheat or multiple seasons of alfalfa hay, generally rest unused in a six- to seven-month window of cool or cold weather.

Cover crops have the ability to take up essential nutrients, including nitrogen, phosphorous and potassium. As the cover crop decomposes, the nutrients become available to benefit the next crop, Higgins said. Cover crops limit soil erosion and improve water quality as they provide a matt of residue to filter surface water. The cover crop can break weed and disease cycles. And some, including root crops like radishes and deep-rooted grasses, can alleviate soil compaction. All of this can lead to greater corn and soybean yields in certain fields.

Read the full article here.

Nitrogen key to uptake of other corn nutrients, study shows

No-Till Farmer reports on research that higher maize (corn) yields in the USA are partly due to modern hybrid varieties taking up more nitrogen after flowering than their older counterparts.

Researchers found that modern hybrids (post-1990) took up 27 percent more total nitrogen from the soil after flowering than pre-1990 corn plants. In fact, nitrogen uptake after flowering in post-1990 hybrids averaged 56 percent of the total grain nitrogen at the end of the season.

Primarily, more grain nitrogen came from new nitrogen uptake from soil during grain filling, as opposed to nitrogen being remobilized from plant leaves and stems. The higher amount and duration of nitrogen uptake contributed to superior grain yields even as actual grain nitrogen concentrations declined.

Optimum nitrogen levels increased plants' abilities to absorb phosphorus, potassium and sulphur. Part of the corn plant's response to receiving adequate nitrogen is that progressively higher percentages of total plant phosphorus, potassium and sulfur end up in the grain fraction at harvest.

Read the full report here.

 

Land degradation causes up to five percent loss in farm output

The Business Recorder reports on a study presented at a recent UN conference which has found that loss of land through desertification and drought costs up to five percent of world agricultural gross domestic product (AGDP), or some $450 billion (340 billion euros), annually.

Each year an area roughly three times the size of Switzerland is lost through soil degradation, it said, as 870 million people suffer from chronic hunger. Between four and 12 percent of Africa's AGDP is lost due to degraded land annually, and in Guatemala the figure is 24 percent, the report said.

The Business Recorder report can be found here and more informaiton about the UN conference is available here.