Category Archives: Soil/Water Science


EcoGEM.  If considering a purchase of calcium sulfate dihydrate (gypsum), it is important to understand the multiple, different benefits and when they take effect. As both a soil amendment and a crop nutrient source, gypsum will remediate sodic soils, help manage saline irrigation waters, provide calcium and sulfur as crop nutrients, and improve soil structure. All of these benefits occur at different rates.

Gypsum works to improve drainage in soils dominated with dispersive clays in four ways. One is immediate, one nearly immediate, the third occurs with a flush of root growth and soil biological activity and the last is a change but sure change in structure. Continue reading THE MULTIPLE BENEFITS OF CALCIUM SULFATE (GYPSUM)

UC Findings: No-Till vs. Conventional Tillage Practices

UC Davis. 19 November 2014.  No-till farming, a key conservation agriculture strategy that avoids conventional plowing and otherwise disturbing the soil, may not bring a hoped-for boost in crop yields in much of the world, according to an extensive new meta-analysis by an international team led by the University of California, Davis.

As the core principle of conservation agriculture, no-till has been promoted worldwide in an effort to sustainably meet global food demand. But after examining results from 610 peer-reviewed studies, the researchers found that no-till often leads to yield declines compared to conventional tillage systems. It still shows promise for yield gains in dryland areas, however. Continue reading UC Findings: No-Till vs. Conventional Tillage Practices

When To Sample Manure For Analysis

Crop Life. 23 September 2014.  Collecting a representative sample for analysis is the single most important factor affecting the accuracy of manure nutrient content.  Obtaining a representative sample is also the most challenging aspect of the manure sampling process. Keep in mind that the sample must represent the actual manure being spread. If sampling is not done correctly, the results of the analysis can be worse than having no analysis at all.

Because only a small amount of manure is sent to the laboratory for analysis, it is imperative that the sample represent the average composition of the manure being applied. The two critical aspects of sampling are the timing of sampling with respect to the manure’s application and the ease or difficulty of the required sampling procedure. Both of these factors are related to variations in nutrient content that occur over time or are present in manure based on how the manure is stored and handled.

Even on a single farm, both weather and management can affect the nutrient composition of manure. Seasonal variations in temperature and precipitation can change nutrient content through dilution, evaporation and volatilization, particularly in uncovered storage and stacks. Manure stored in barns as bedded pack or litter or stored in covered stacks is typically not affected by weather, but there is often significant variation in nutrient content throughout the manure based on the uneven mixing of bedding, hay and/or spilled feed. Finally, a single liquid manure source can have a large variation in nutrient content if the manure is not thoroughly agitated and mixed before spreading.

When is the ideal time to collect a manure sample? Because the goal is to collect a sample that represents the manure actually being applied, the best time to sample is during loading or field application. The sample can be obtained during loading of manure application equipment or in the field as the manure is being spread. Sampling at this time has several advantages:

  • The time-related changes in nutrient content caused by management and weather are minimized.
  • The non-uniformity due to lack of mixing is reduced. Subsamples can be taken as the manure is loaded, which results in more representative samples.
  • The difficulty of collecting representative samples while manure is in the storage, barn, or stack is reduced.
  • The complexity of the sampling equipment required is reduced.
  • In some cases, the sampling procedure is safer,reducing the risk of falling in or being overcome by gases.

There is one disadvantage to sampling during spreading: the analysis results from samples collected at this time will not be available to calculate manure application rates for that application. However, the results can be used to calculate future application rates. It is recommended that the manure nutrient content values used in calculating manure application rates be based on running averages or baseline values. To obtain these values, each manure group should be sampled annually for three to five years. After the initial period, manure can be sampled periodically to monitor the nutrient values. If there are changes in feeding programs or manure storage and handling, the manure should be re-sampled. As long as no significant changes are made in the production system, the nutrient content of the manure should remain fairly constant.

Some states may have specific regulatory requirements related to manure sampling that may vary from the general guidance provided above and elsewhere in this fact sheet. When developing a manure sampling program, farmers, consultants, and nutrient management planners should learn and integrate their state regulatory requirements with the guidance outlined in this fact sheet.


EcoGEM Correcting poor soil structural conditions with an application of calcium sulfate (gypsum/anhydrite) can have a significant impact on soil tilth and crop yields. However many producers overlook this practice because they are not aware of the benefits to soil structure as well as a readily available source of calcium and sulfur.

One important aspect of calcium sulfate is that it is soluble and reacts quickly regardless of particle size. Compare that to lime that requires time since it is not very soluble. The general practice for lime is to apply in the fall, lightly incorporate and then during the next 6 to 8 months it will dissolve and react in the soil.

The exact amount of time it takes for lime to react is based on particle size and soil moisture. Smaller particles have more surface area, and react faster in the soil. For powdered ag lime, particles smaller than 60 mesh will dissolve and react within 30 days. As particle size increases, the dissolution rate slows, since the particle’s surface area decreases as particle size increases. Particles between 30 and 60 mesh take 1 to 2 years to react, while particles between 8 and 30 mesh take as long as 5 years. Powdered ag gyp (even when pelletized) is often smaller than 100 or 200 mesh and in addition it is soluble so gypsum’s solubility is measured in days if moisture is available, not weeks or months as is the case with lime.

You can’t base a calcium sulfate application on a routine soil test because they weren’t designed to make these recommendation. For lime, a soil test measures water pH and buffer pH and this information is used to determine a lime recommendation to correct an acid soil pH. A soil test can calculate a soil’s cation exchange capacity and that information can be used to set a calcium sulfate rate. A heavier soil with a higher CEC would require more calcium sulfate than a lighter (sandier) soil with a low CEC. A routine soil test will also measure calcium and sulfur but it doesn’t measure soil structure. Soil testing to determining a gypsum application rate is not a well-defined science yet.

Calcium sulfate can come from several sources including mined and synthetic by-products and all are substantially equivalent in turns of calcium sulfate but differ in purity. What about the calcium sulfate content? Most ag gyp products contain calcium sulfate in varying amounts from 60% to greater than 95% – this is referred it as purity. Deposits often contain some limestone and other minerals.

Applying calcium sulfate as a source of calcium and sulfur and to improve soil structure is a good practice. Determining the appropriate rate depends on economics and product type. By-products are usually applied at 0.5 to 1 ton per acre every 3 or 4 years while pelletized ag calcium sulfate is applied at 200 to 400 lbs. per acre every 1 to 2 years.

Global Slow-Release Fertilizer Market Growing

American Society of Agronomy. The global controlled-release fertilizers market was valued at $2,061.2 million in 2013 and is projected to grow at a CAGR of 6.5% from 2014 to 2019. Controlled-release or slow-release fertilizers (CRFs or SRFs) are also known as enhanced efficiency fertilizers. These fertilizers release nutrients slowly or gradually into the soil at a pre-determined time and rate. Controlled-release fertilizers are gaining importance due to the global awareness of sustainable agriculture which demands step-by-step reduction in the cost of farming and meets environmental safety standards. These fertilizers are applied by topdressing, or soil mixing prior to sowing.


Iron chlorosis is a yellowing of plant leaves caused by iron deficiency. However it is not always a true iron deficiency but rather an iron tie-up in plants and soil. Yellow leaves indicate a lack of chlorophyll, the green pigment responsible for photosynthesis (sugar production) in plants.The causes of iron chlorosis are complex and not completely understood. It could be a deficiency in the soil or the plant or an iron tie-up in the soil or plant. Many reactions govern iron availability and make iron chemistry in the soil complex. Iron chlorosis generally occurs in soils with a high pH and are calcareous. Even though these soils have plenty of iron, the high pH causes chemical reactions that make the iron unavailable to plant roots

Plants that are native to high pH soils have evolved and don’t illustrate symptoms of iron chlorosis, because they are efficient in iron use and can obtain iron from the soil. Recent research has discovered that bicarbonates (HCO3) plays a major role since they are readily produced in high pH soils, especially when more moist conditions limiting iron availability. Even in alkaline soils, bicarbonate is much higher in the calcareous soil than in the non-calcareous soil.

In calcareous soils, bicarbonate inhibits mobilization of accumulated irons from roots to foliage and affects availability of iron in the soil by buffering soil pH. When irrigation water high in bicarbonate is applied, iron deficiency is enhanced because bicarbonate is supplied to the soil. The adverse effects of high bicarbonate levels are exacerbated in saturated soils, very dry soils, or compacted soils, where bicarbonate levels increase, leading to diminished root growth and nutrient uptake.

By |September 2nd, 2014|

“Peak Soil” Threatens Future Food Security And Supply

Reuters. 17 July 2014.  The challenge of ensuring future food security as populations grow and diets change has its roots in soil, but the increasing degradation of the earth’s thin skin is threatening to push up food prices and increase deforestation.

    While the worries about peaking oil production have been eased by fresh sources released by hydraulic fracturing, concern about the depletion of the vital resource of soil is moving center stage.

    “We know far more about the amount of oil there is globally and how long those stocks will last than we know about how much soil there is,” said John Crawford, Director of the Sustainable Systems Program in Rothamsted Research in England.

    “Under business as usual, the current soils that are in agricultural production will yield about 30 percent less than they would do otherwise by around 2050.”

Surging food consumption has led to more intensive production, overgrazing and deforestation, all of which can strip soil of vital nutrients and beneficial micro-organisms, reduce its ability to hold water and make it more vulnerable to erosion.

Such factors, exacerbated by climate change, can ultimately lead to desertification, which in parts of China is partly blamed for the yellow dust storms that can cause hazardous pollution in Asia, sometimes even severe enough to cross the Pacific Ocean and reduce visibility in the western United States.

Arable land in areas varying from the United States and Sub-Saharan Africa, to the Middle East and Northern China has already been lost due to soil degradation.

    The United Nations‘ Food and Agriculture Organization (FAO) has estimated that 25 percent of agricultural land is highly degraded, while a further 8 percent is moderately degraded.


Crawford said the degradation of soil could in theory lead to more land being bought into agricultural production, which would deal a serious blow to efforts to stem climate change, since clearing forests for farmland leads to a heavy net increase in greenhouse gases.

    “If we keep treating our soil the way we do, we will have to convert about 70 percent of the earth’s surface into agriculture to meet demand for food by 2050 (from about 40 percent now),” Crawford said.

That is in part because there will be many more mouths to feed. The United Nations has projected that global population will reach 9.6 billion by 2050, up from 7.2 billion last year.

Emerging nations are also embracing Western diets that include more consumption of meat, which will add further to the strain on agricultural resources.

    Crawford also noted that moderately degraded soil could only store about half the amount of water of good soil, adding to pressure on limited water resources.

“We need to find ways of pricing the true cost into food, including the environmental cost of soil degradation,” Crawford added.

Food security became a hot topic after record high grain prices in 2008 marked the start of a period of volatility.

Agricultural markets are still unstable, after near-record prices in 2012 prompted increased production, which led to surpluses. [ID:nL6N0PM324]

Prices have since fallen back on the rebound in production and global stocks, with decent harvests expected in several major grain producers including the United States this year, but there’s a risk of complacency on the long-term outlook.

“We are trying to make sure when we talk about food security we talk about healthy soil. The link has been missing to some extent,” said Moujahed Achouri, Director of the FAO’s Land and Water Division.

    “We do believe there that now there is momentum (to tackle the soil problem).”

Price pressure and ultimately margin pressure can lead to farmers taking shortcuts to achieve something in the short term at the expense of the long term, said Nicholas Lodge, managing partner at Clarity, a Gulf-based agricultural investment firm.

“You can really have a harmful impact on soil in as little as one season,” said Lodge.

“If you happen to have damaged the soil and you’re losing the top soil, it’s not then an easy matter to repair that situation or replace that soil.”


    One of the main drivers of soil degradation has been the trend towards less diversity in agriculture.

    “In a lot of agriculture it has become a monoculture, so you just don’t get the diversity of plants that are necessary for healthy soil, and often the agricultural practices are all about mining the soil rather than managing it,” said Tim Hornibrook, head of Macquarie Agricultural Funds Management Limited.

    Vietnam is one example of a country where there has been an increased focus on one crop with a huge surplus of robusta coffee grown to export to the global market.

    The U.S. Department of Agriculture also estimates that corn will be harvested on around 177 million hectares this year, a rise of around 65 percent over the last 50 years.

    “Farming with monocultures leads to decreased productivity,” Hornibrook said.

Excessive use of fertilisers can also cause damage to soil, at times altering its acidity or salinity in ways that reduce microbial activity and therefore ultimately plant growth.

More education in the farming sector on how to conserve soils, along with better use of technology, is expected to help tackle the problem.

    “Technology which can help includes imagery which allows you to do soil mapping of what mineral and nutrients are in the soil and applying fertilizer according to the requirement of each individual area of the farm,” said Hornibrook, adding that investment was challenging as the sector was fragmented and capital starved.

    “The issue doesn’t get addressed without capital. Investing in your soil costs money and therefore the ultimate way to incentivise farmers to do it is higher food prices.”

But higher prices alone won’t encourage consumption patterns that provide a healthy balance for both people and soil.

“Consumers make choices largely on price, farmers make decisions largely on profit,” Crawford said, adding there was no clear incentive to encourage behavior that benefited health or the environment.

“We need to try and encourage better diets from a health and environment point of view.”


Christian Science Monitor. 15 July 2014. [NOTE: This article originally appeared at Food Tank, a think tank focused on feeding the world.]

One of the most overlooked ingredients in farming exists right beneath farmers’ feet—healthy, fertile soils. 
 Unfortunately, this vital ingredient is being degraded and eroded at unprecedented rates across the world. According to the U.N. Food and Agriculture Organization (FAO), 25 percent of the planet’s land is highly degraded, and only 10 percent is improving.
 All continents are experiencing land degradation, and the loss of soil quality is not only an issue for farmers, but for all of us.
 Deforestation, for example, is causing China‘s Loess Plateau to erode rapidly. Overgrazing of grassland in the Western United States is reducing soil depth and creating desertification. In India, overcutting trees and crops is reducing soil fertility and threatening wild medicinal plants. Farmland plowed for commercial agriculture around the world exposes topsoil and increases erosion. In fact, Brazil loses 55 million tons of topsoil every year because of soybean production.
 But agriculture doesn’t have to degrade soils—it is possible for food production to enrich the Earth, restore nutrients, conserve water, and prevent further erosion.
 This week, Food Tank is recognizing 14 exciting projects and individuals who are facilitating important dialogue about the importance of soil and actively addressing the threats of soil degradation and erosion around the world.
 1. The documentary film Dirt! The Movie creates a conversation about the under-appreciated source of life and material beneath our feet. The film brings together geographically diverse stories of soil restoration and connects the environmental, economic, social, and political importance of soil.
 2. Founded in Sarajevo, the Center for Forestry and Environmental Action works to rebuild and replenish areas in Bosnia and Herzegovina and the surrounding region. The organization provides practical and professional support to farmers and businesses, by promoting sustainable planting and agricultural practices.
 3. Perennial grain crops may also help prevent soil degradation, particularly in sub-Saharan Africa. Michigan State University is examining the ability of perennial grains to reduce soil erosion in five African countries including Ghana, Mali, Malawi, Tanzania, and Ethiopia.
 4. The Green Asia Network actively works to combat desertification across the expanses of northern Asia. In Mongolia, China, Russia, and other central Asian countries, this organization fund raises to reforest barren landscapes, educate local citizens and farmers on the detriments of soil degradation, and hosts festivals and cultural exchanges highlighting successful efforts being made to improve soil quality and farming practices.
 5. The Land Institute, based in Salina, Kansas, works to support sustainable farming and combat destructive agricultural practices while promoting polyculture systems. The Institute views the degradation of soil as a contributing factor to a host of other environmental problems, including declining crop yields, increasing greenhouse gas emissions, and dead and contaminated zones resulting from toxic runoff.
 6. The International Erosion Control Association (IECA) highlights solutions to slow soil degradation and erosion in Central and South America. Through education, public events, and on-site consultations, IECA promotes sustainable efforts to improve soil quality in the region.
 7. Matt Liebman, the Henry A. Wallace Chair for Sustainable Agriculture at Iowa State University, envisions a future for Iowa where farming practices protect soil and water quality. His research includes livestock reintegration and organic soil management. Liebman found more diverse and longer crop rotations can greatly reduce fertilizer, herbicide, and fossil fuel inputs while increasing crop yields.
 8. Agronomist Roland Bunch presents sustainable solutions to soil degradation through the use of cover crops and green manures in his book Restoring the Soil. Cover crops and green manures can improve soil fertility and control weeds by increasing organic matter in the soils without the use of expensive inputs.
 9. Sustainable Organic Integrated Livelihoods (SOIL) is a non-profit organization “dedicated to protecting soil resources, empowering communities and transforming waste into resources in Haiti.” Co-founded in 2006 by Dr. Sasha Kramer and Baudeler Magloire, SOIL utilizes EcoSan or ecological sanitation, a “low cost approach where human wastes are collected, composted, and recycled for use in agriculture and reforestation.”
 10. The Savory Institute supports sustainable grasslands through holistic management practices. Through research regarding productive methods of care, informing and shaping political policy, identifying and establishing market incentives, and increasing public awareness, the organization strives to remove global barriers to successful land management in order to support soil.
 11. In the United Kingdom, the Soil Association campaigns for humane, healthy, and sustainable food, farming, and land use. Founded in 1946 by a coalition of scientists, nutritionists and farmers, the Soil Association supports and promotes best practices by farmers and brings food systems closer to organic principles. The Association inspects and certifies organic farms and businesses.
 12. Scientists have compiled the first soil atlas of Africa to help the general public, policymakers, land users, and scientists understand and manage the continent’s key resource. The 176-page atlas aims to inform stakeholders of the continent’s varying patterns of soil, and the need to conserve and manage it sustainably.
 13. Rodale Institute is committed to research in organic agriculture, improving soil, and advocating for practices that support farmers. The Institute started the Farming Systems Trial (FST) in 1980: the United States’ longest running side by side comparison of chemical and organic agriculture. Results for more than 30 years have shown organic yields match or are greater than conventional yields.
 14. The International Fund for Agricultural Development (IFAD) implemented the Soil and Water Conservation and Agroforestry Program (SWaCAP) in the Kingdom of Lesotho, where most of the soil is derived from sandstone or shale. The objectives of SWaCAP are to promote soil and water conservation as part of farmer’s normal agricultural activities and in a way that increase yields and incomes.
 These projects show that the ground beneath our feet may be the most important ingredient in alleviating hunger and poverty across the world. What are other projects in your community protecting soil for future generations?