Gypsum’s Role in Worldwide Rice Production

Brent Rouppet, Ph.D., Agronomist

Rice (Oryza sativa L.) is the most important human food crop in the world, directly feeding more people than any other crop. In 2012 (latest data) nearly half of world’s population, more than 3 billion people, relied on rice every day. It is the staple food across Asia where approximately half of the world’s poorest people live, and is becoming increasingly more important in Africa and Latin America. Ninety percent of the world crop is grown and consumed in Asia. Rice is the only major cereal crop that is primarily consumed by humans directly as harvested, and only wheat (Triticum aestivum) and corn (Zea Mays L.) are produced in comparable quantity (source: Infoplease.com).

Rice has fed more people over a longer time than has any other crop. It is especially diverse both in the way it is grown and how it is used by humans. Rice is unique because it can grow in wet environments that other crops cannot survive in. Such wet environments are abundant across Asia. The domestication of rice ranks as one of the most important developments in history and now thousands of rice varieties are cultivated on every continent except Antarctica. (source: ricepedia.org)

Though rice is a staple food for half of the world’s population, farmers need to produce more food in less area since agricultural land use is diminishing day by day. The world population is

expected to be exceeded 9 billion by 2040 with an increase of about 50% in less than 40 years (U.S census Bureau, Population Division, 2009). Therefore, production of enough food to feed the growing world population is a continuous challenge for farmers.

While the current world population is over 7.5 billion, it is projected to be 9.8 billion by the year 2050. Already of the 7.5 billion, 2 billion people suffer from malnutrition and hunger is soaring to levels without modern precedent. Now farmers, agronomists and soil scientists are being called upon to do an additional job of producing the extra food.

Among the yield limiting factors of rice, several soil conditions play an important role that affect the quality and quantity of all agricultural crops. In irrigated agriculture worldwide, the number one issue that growers are facing is soil structure related problems, and these problems are escalating. There are specific problems for plant growth and production in saline and sodic soils; especially poor soil structure which limits water and air infiltration, and root penetration into the soil. Reclamation of these soils requires the leaching of exchangeable sodium and other harmful salts from the root zone.

How Gypsum (CaSO4.2H20) Can Help Worldwide Rice Production:  The only way improved soil structure has been accomplished worldwide is with the application of calcium sulfate products, mainly gypsum. The calcium removes the sodium and magnesium from the cation exchange sites, and now these ions can be leached down through the soil profile. Other calcium products simply cannot supply enough calcium to get the job done. High levels of sodium and magnesium are especially detrimental to overall soil health.

Climatic changes, especially water shortage, have also driven agronomists and soil scientists to develop production technologies for cultivation of rice under limited water conditions. Developing technologies to save water such as cultivation of direct seeded rice by drum seeder, maintain of alternate wetting and drying condition in rice field, plus the use of gypsum have proved to make rice production much more productive under limited water conditions.

A field experiment was conducted on a zinc deficient highly deteriorated sodic soil of the Ghabdan soil series in Asia to determine the effect of different rates of gypsum and different rates of zinc on rice production. Gypsum application significantly increased yield and zinc uptake in rice due to a significant decrease in soil pH and increase in calcium and zinc supply. Zinc application alone significantly increased soil and plant Zn but yields were poorer than with gypsum application alone because of calcium deficiency and/or sodium toxicity. Zinc applied together with gypsum markedly increased yield and zinc uptake. (source: researchgate.net).

Also, investigations on the nutritional aspects of calcium in improving rice growth and yield were conducted in solution and soil cultures in naturally salt-affected fields. In the case of solution culture, gypsum was applied in the presence of sodium chloride salinity. Three rice cultivars of differential salinity tolerance were used. Application of gypsum proved to increase panicle length, number of tillers, paddy and straw yield under both saline and saline sodic soils as well as in naturally salt affected field. Also, seed setting was improved in all the three cultivars (Source: Soil Science Society of America Journal).

Gypsum has been proven to help soils and plants for myriad reasons since in nature it is unique and incomparably versatile and multifunctional. This naturally mined product serves without equal as a fertilizer, a soil conditioner and a soil amendment.

Major benefits of high-quality gypsum:

• An excellent fertilizer source for calcium and sulfur. With calcium and sulfur deficiencies appearing more and more frequently worldwide, gypsum is a practical and economical source of these essential nutrients.
• Improves soil structure and compacted soils. Water penetration problems cause ponding and runoff, depriving root systems of needed moisture and oxygen, and wastes irrigation water.
• Amends and reclaims soils high in destructive sodium and magnesium. Sodium and magnesium (to a lesser extent) act the opposite as calcium in soils by destroying structure and reducing water, air movement and root growth.
• Replaces harmful salts. Sodium, chlorine and many other salts in higher levels in irrigation water and soil are detrimental to plant growth.
• Helps with high bicarbonate irrigation water. Bicarbonates form free lime when water evaporates resulting in reduced available calcium and increased soil pH.
• Enhances water use efficiency. Twenty-five to 100 percent more water is available in gypsum treated soils vs. untreated soils; less irrigation water is required to achieve the same results.
• Reduces runoff, erosion and soil crusting. Aggregates stabilized by gypsum are less prone to crusting and erosion since there is limited runoff due to larger, more stable aggregates.
• Along with humic acid, composts, manures and other plant materials, use of gypsum helps rebuild the supply of soil organic matter.

It has been stated that gypsum’s routine and frequent application is actually necessary for the sustainability of all irrigated soils.

AG COMPANIES WILL START TO LOOK AT THEIR INVENTORY LEVELS GOING FORWARD.

With the recent closures of several meat processing plants (Smithfield Foods, JBS, Tyson, and Cargill, among others), what will it mean to the food supply system in America?

It could mean a significant change in how companies look at inventory, says Jack Bobo, the CEO of Futurity, a food and agriculture consultant. “There’s going to be a need to rethink what inventory means,” Bobo says.

Today, companies have evolved into a just-in-time inventory system, in order to reduce costs, they increase efficiency and speed to market. This could change in light of the COVID-19 pandemic and access to food supplies, according to Bobo. “There’s a real danger in not having inventory on hand,” he says. Bobo made his comments April 14 on a webinar entitled, “Food & Supply Chain in a COVID-19 World” that was sponsored by The Land Report and Peoples Company.

Companies will think long and hard about not having inventory vs. the reduced risks of having inventory on hand coming out of this pandemic, he says.

Bobo’s outlook isn’t dire, however, especially for the ag sector. We should assume that facilities will reopen, Bobo says. There will be continued consumer demand – even pent-up demand near the end of the year, since people have spent several months NOT spending.

Things will be better for the ag sector more than other sectors, Bobo said, because people need to eat.

PLANT-BASED FOODS

How will the current strain on the food supply system affect the plant-based movement in the United States? According to Bobo, “it’s definitely going to accelerate the conversation” but may not impact sales of alternative foods. As the price of beef rises, consumers may try protein alternatives, he says; on the other hand, animal products will become more in demand – a “premiumization” effect of the high-quality perception of meat.

SOURCE: Successful Farming 4/14/2020

Bobo does see a continued growth in sales of plant-based products, but farmers and the agriculture industry shouldn’t be too concerned. “Many people in ag feel they are under attack or under siege,” Bobo says. When we look forward to 2050, we need to double the amount of proteins produced on Earth, saying it could be a $4 trillion business in 2050. “There’s room for everybody in this.”

READ MORE: How organic and local food markets are affected by COVID-19

Hamburger is a good example in the U.S., where 50% of hamburger is imported. If the plant-based market grows, we would still produce 50% of the hamburger needed; it will just lower our imports, and not impact producers here.

The biggest impact may not be on the plant-based alternatives, Bobo says. “I don’t think there’s a great concern about it. But it is undermining the confidence in our food supply between food producers and plant-based producers,” he says.

“It undermines faith in our food system, generally, and that doesn’t help anybody.”

Experts predict that advances in science and technology will keep farmers and agriculture professionals on their toes.

By 2020 there will be an even higher demand for skilled people in the agricultural sector, with top careers including technologists, hydrologists, food scientists, agricultural communicators and precision agriculture technologists.

While the spectrum of opportunity is vast, the role of soil scientists, particularly in Africa where farmers are faced with serious health issues, remains critical. The UN Food and Agricultural Organisation (FAO) estimates that more than 50% of Africa’s agricultural land has serious soil problems, including nutrient depletion, soil acidity and erosion.

These challenges not only limit productivity, but also African farmers’ ability to produce enough food.

Laeveld Agrochem marketing director Corné Liebenberg points out that the African continent is the largest geographical area with growth opportunity.

“Africa is comprised of the most unused arable land of all the continents. The whole world is looking to Africa for adequate food production and to prevent a global food crisis,” he says.

For Laeveld Agrochem, this multiple challenge has led to the founding of Agri Technovation, a company that formulates and manufactures a range of specialised nutrition and soil health products meeting crop-specific nutrient, stimulant and energy requirements, while promoting plant and soil health.

According to the National Development Plan, the agricultural sector is expected to create about one million jobs by 2030.

This means there is a need and scope for innovative and motivated young people to become part of the agricultural sector, which continues to be an important pillar for economic growth for South Africa.

source: the Mercury 

As innovation, technology, and data assessment advance agricultural production, and as our scientific understanding of plant nutrition, soil health, and climate increases, the fertilizer industry’s farmer-customers require our professionals to have the knowledge and tools that will help them be productive and profitable.

The Fertilizer Institute (TFI), committed to being a resource for the industry by providing sound, science-based information to help fertilizer manufacturers and retailers serve their customers.

TFI in 2019 acquired several resources from the former International Plant Nutrition Institute (IPNI). This acquisition helps ensure that the wealth of information IPNI produced for agricultural production remains available for years to come. TFI provides a variety of resources:

• Several publications, including the newly revised Soil Fertility Manual and the CCA Study Guide, now available on TFI’s online store at store.tfi.org.
• TFI assumed leadership for the Foundation for Agronomic Research (FAR), which administers the 4R Research Fund. More information on FAR and the supported 4R research findings are available at 4Rresearch.org.
• The InfoAg Conference is now in TFI’s meetings portfolio. The conference focuses on sharing knowledge on advances in modern agriculture through innovative products, tools, and technology to implement 4R Nutrient Stewardship and enhance nutrient-use efficiency.
• Soil Test Survey and Nutrient Use Geographic Information System (NUGIS) help inform the fertilizer industry and our stakeholders about local- and state-level nutrient trends that are essential for advancing 4R Nutrient Stewardship. TFI is ensuring these IPNI-initiated programs remain available to the agronomy community.

The Soil Fertility Manual was recently updated in 2019. Since 1978 the manual has helped fertilizer retailers, crop advisers, extension agents, and agronomists give farmers sound agronomic advice. In addition, the manual is used on university campuses to educate tomorrow’s crop advisers on agronomic practices. While agriculture has changed since the manual was first published, the basic principles of soil fertility and agronomy have not. The book is a resource for implementing efficient nutrient management, such as the 4R Nutrient Stewardship principles (applying the right fertilizer source, at the right rate, at the right time, and at the right place).

Additionally, TFI has partnered with the American Society of Agronomy (ASA) to offer online learning opportunities for agronomists to learn more about nutrient management. There are a suite of classes relating to the 4Rs, along with several classes about integrating micronutrients, such as zinc and boron, into fertility management plans. A listing of classes is available at agronomy.org/education/classroom/classes. More webinars are planned for 2020, so follow the 4Rs on Twitter at @4RNutrients for the latest updates.

These ASA classes offer CCE credits for certified crop agronomists (CCA) to maintain their certification. TFI also makes credits available at two conferences throughout the year. More than 1,300 CCAs, crop advisors, and fertilizer retailers convene each July for the InfoAg conference. The 2020 conference will be held in St. Louis, MO, July 28-30. This year’s conference will feature new content focusing on in-field nutrient management and application decision making, economic analysis to support practice change, and integrating precision ag technologies into management plans that include new and emerging products and technologies. Attendees will also continue to hear about the latest in precision agriculture technologies, data management, and practice implementation that have long been topics at the conference. Information on the agenda and registration can be found at infoag.org.

Following InfoAg, TFI will present the T3 conference in November. Previously known as the Fertilizer Outlook and Technology Conference, T3 will educate attendees on the latest in fertilizer technology, trends, and transportation. This year’s T3 conference will be held Nov. 4-6 in West Palm Beach, FL. More information about this year’s conference will be available this summer at tfi.org.

The fertilizer industry is home to thousands of highly skilled professionals, but as the industry changes with new technologies and a deeper understanding of nutrient science, TFI is a trusted resource and source of information, ensuring success for years to come.

SOURCE: JENNIFER MARTIN CROPLIFE

Nitrogen Management Practices to Improve Crop Nitrogen Use Efficiency and Minimize Nitrogen Losses to the Environment

Basic recommended rates are determined based on your soil test report by looking at the planned crop and the expected yield for that crop. The amount of residual nitrogen in the soil must then be taken into account and subtracted from the recommendation. This includes previous manure applications and carryover N from previous legumes. Also, if fertilizer, such as a starter containing N, is applied regardless of manure applications, this N should also be taken into account. You need to account for these credits by subtracting them from the basic soil test recommendation (Figure 2). The resulting number will give you the rate you need to apply this year as fertilizer, manure, or other source of N.

Figure 2. Net crop nitrogen requirement.

• Do not apply nitrogen in excess of crop recommendations. Having an approved nutrient management plan can help you with this. See your soil test for the recommended rate and be sure to take into account the planned incorporation time, previous manure, and legumes.
• Manure application rates should be based on meeting the net crop need after all other sources of N either in the soil (legume N, manure residual N) or added N (starter fertilizer, N applied with herbicides) have been accounted for.
• Manure N availability to the crop is lower than the total amount of N in the manure. Thus, more total manure N must be applied to achieve the same results as would be needed using fertilizer to meet the same net crop requirement. However, manure N availability increases with optimum manure application management. The goal for optimum manure N management is to reduce the total N applied in manure to as close as possible to the amount that would be required as fertilizer.
• Best management such as applying manure in the spring, incorporating it immediately following application, and cover cropping will generally result in the highest manure N availability, less than two times the amount of fertilizer N that would be required to meet the net crop requirement. With good manure management, the total amount of manure N applied should be less than three times the fertilizer N requirement to meet the net crop requirement. Acceptable but less efficient manure N management may require more than three times the total manure N compared to fertilizer to meet the net crop requirement. See the Manure Nutrient Management section of the Penn State Agronomy Guide for information and instructions for making these critical calculations.
• Use the PSNT (pre-sidedress soil nitrate test) or chlorophyll meter to guide sidedress fertilizer nitrogen applications. The PSNT measures nitrate in the soil right before the highest amount of crop uptake. The chlorophyll meter test estimates the nitrogen status of growing corn by measuring the greenness of the leaves. Both of these in-season tests improve N recommendations significantly in most situations, particularly when manure is being used.
• Where appropriate, use new technologies such as on-the-go sensors and aerial photography that can provide useful information about the N status of crops, improve N recommendations, and enable variable-rate N application. Variable-rate N application has potential to improve crop yields and limit N environmental losses based on crop growth status and its interpretation for changing N rate application versus the traditional whole-field uniform-application-rate approach. Keep up on the latest technologies as they are developed and evaluated, and determine how they might fit into a program to improve N management on your farm.

SOURCE: PENN STATE EXTENSION

While farmers have used gypsum (calcium sulfate dihydrate) for centuries, it has received renewed attention in recent years. This resurgence is due in large part to ongoing research and practical insights from leading experts that highlight the many benefits of gypsum.

The latest information on gypsum has been covered in detail at past Midwest Soil Improvement Symposiums. The event — which has been held in conjunction with The Ohio State University’s Conservation Tillage and Technology Conference — typically includes presentations from industry representatives, scientists, consultants, and growers on the use of gypsum to improve soil structure, reduce nutrient runoff, and more.

Here are five key (and overlapping) benefits of gypsum highlighted at past symposiums:

1. Source of calcium and sulfur for plant nutrition. “Plants are becoming more deficient for sulfur and the soil is not supplying enough it,” said Warren Dick, soil scientist and professor, School of Environment and Natural Resources, The Ohio State University. “Gypsum is an excellent source of sulfur for plant nutrition and improving crop yield.”

Meanwhile, calcium is essential for most nutrients to be absorbed by plants roots. “Without adequate calcium, uptake mechanisms would fail,” Dick said. “Calcium helps stimulate root growth.”

2. Improves acid soils and treats aluminum toxicity. One of gypsum’s main advantages is its ability to reduce aluminum toxicity, which often accompanies soil acidity, particularly in subsoils. Gypsum can improve some acid soils even beyond what lime can do for them, which makes it possible to have deeper rooting with resulting benefits to the crops, Dick said. “Surface-applied gypsum leaches down to to the subsoil and results in increased root growth,” he said.

3. Improves soil structure. Flocculation, or aggregation, is needed to give favorable soil structure for root growth and air and water movement, said Jerry Bigham, Professor Emeritus, School of Environment and Natural Resources, The Ohio State University. “Clay dispersion and collapse of structure at the soil-air interface is a major contributor to crust formation,” he said. “Gypsum has been used for many years to improve aggregation and inhibit or overcome dispersion in sodic soils.”

Soluble calcium enhances soil aggregation and porosity to improve water infiltration (see below). “It’s important to manage the calcium status of the soil,” he said. “I would argue it’s every bit as important as managing NPK.”

In soils having unfavorable calcium-magnesium ratios, gypsum can create a more favorable ratio, Bigham added. “Addition of soluble calcium can overcome the dispersion effects of magnesium or sodium ions and help promote flocculation and structure development in dispersed soils,” he said.

4. Improves water infiltration. Gypsum also improves the ability of soil to drain and not become waterlogged due to a combination of high sodium, swelling clay and excess water, Dick said. “When we apply gypsum to soil it allows water to move into the soil and allow the crop to grow well,” he said.

Increased water-use efficiency of crops is extremely important during a drought, added Allen Torbert, research leader at the USDA-ARS National Soil Dynamics Lab, Auburn, AL. “The key to helping crops survive a drought is to capture all the water you can when it does rain,” he said. “Better soil structure allows all the positive benefits of soil-water relations to occur and gypsum helps to create and support good soil structure properties.”

5. Helps reduce runoff and erosion. Agriculture is considered to be one of the major contributors to water quality, with phosphorus runoff the biggest concern. Experts explained how gypsum helps to keep phosphorus and other nutrients from leaving farm fields. “Gypsum should be considered as a Best Management Practice for reducing soluble P losses,” said Torbert, who showed studies on how gypsum interacts with phosphorus.

Darrell Norton, retired soil scientist at the USDA-ARS National Soil Erosion Research Laboratory at Purdue University, added: “Using gypsum as a soil amendment is the most economical way to cut the non-point run-off pollution of phosphorus.”

SOURCE: CROPLIFE

NUTRIENT BUDGETING

Budgeting is fundamental to BMP for nutrients. First, the budget must take into account the amount of nutrients a grower expects the crop to take up and, subsequently, leave the system in the crop biomass. This amount will vary among crop species as well as among levels of productivity within the same species. For example, a corn crop that yields 100 bushels/acre (5600 lbs) will export (meaning that nutrients leave the field in the harvested portion of the plant) approximately 80 lb/acre of N in the grain and 60 lbs/acre of N in the stover (which is above-ground biomass that is not grain and includes stalks/stems and leaves). If the corn crop were to yield 80 bushels/acre, those numbers would be reduced by 20%. Compare that with an iceberg lettuce crop that yields 40,000 lbs/acre. This will export approximately 80lbs/acre of N from the field, all in the above-ground biomass (since the whole above-ground portion of the plant is harvested). How does one figure such numbers out? There is information available for prominent crops via extension services and other online tool. However, it is also possible to estimate these numbers by multiplying the concentration of a nutrient by the quantity of biomass that contains that concentration. (For example: Corn grain contains about 1.4% N at harvest. Therefore, for a 3 ton/acre crop, the amount of N leaving the field in the grain is 6000lbs x 0.014 = 84lbs/acre N.

In order to anticipate the amount of nutrients likely to be exported from the field in the crop biomass, a grower must consider in advance what a reasonable yield goal is for the crop s/he is growing. If the grower has had previous experience with the crop at the same location, this is often a good guide. Also, trying to get a general idea of typical yields for the crop and region in question can be an important step. This information might be gained by consulting with other growers, with a professional crop consultant, and/or a university extension agent, such as the UCANR Statewide Integrated Pest Management Program, the UC Vegetable Research and Information Center, the UC Manure Management Crop N Uptake Calculator and the UCANR Soil Fertility Management Guide for Fresh Market Tomato and Pepper Production. It is important that the yield goal not be a “yield wish”. Fertilizing for a crop yield that is not attainable in a given context (due to inherent biophysical and/or management constraints) is a very easy way to over-budget the fertility needed and create an opportunity for nutrient pollution in connected water bodies.

No crop will use fertilizers with 100% efficiency. In fact, 60-70% efficiency is generally as good as can be accomplished, and many of the most common crops grown in California are estimated to have much lower average efficiencies. The reasons are that 1) plants are often in competition for nutrients with the micro-biota in the soil and 2) nutrient losses via the movement of water and gas are an inherent part of a dynamic, productive biological environment. However, applied fertility that goes unused by a given crop can still be incorporated into the plant-soil system by using cover crops, rotating with crops that have distinct root systems and nutrient uptake patterns, and by other management practices that are soil building. A fertile soil with a high nutrient supplying capacity can compensate for a fertilizer deficiency in the short to medium-term. Conversely, a less fertile soil may require more applied nutrients than the above ground portion of the crop will use in order to account for the fertilizer use inefficiency and the low nutrient supplying capacity of the soil. For this reason, soil fertility testing is an important part of determining the right amount of nutrients to add. However, interpretation and application of soil tests varies greatly from crop to crop and across environments.

SOURCE: California Agricultural Water Stewardship Initiative

Nutrient management is among the most consequential decisions that a grower makes with respect to water quality and crop productivity. Because crops do not take up fertilizer with 100% efficiency, many growers apply organic and inorganic fertility in excess of crop demand to ensure that nutrients are not limiting to their crops. While this is often an economic decision, adding excess nutrients to the crop-soil system also creates an opportunity for nutrient losses from farms into the surrounding environment. One major loss pathway for excess nutrients is via nutrient-enriched water that drains from the surface of agricultural fields or percolates beyond the root zone of the crop and into groundwater storage. Nitrogen (N) and phosphorus (P) are generally the most limiting nutrients to crop growth, and are, therefore, added in the greatest quantities by growers and most frequently the nutrient constituents of concern in agriculturally connected waterways and aquifers. When present in excess, nitrates and phosphates can create environmental problems such as eutrophication of waterways, algal blooms, and contamination of drinking water. Recent research in the Tulare Basin and Salinas Valley has found that nitrate pollution of groundwater supplies is widespread and overwhelmingly the result of the agricultural activities in the area over the past six decades. As a result of this study, new regulations on N management have been introduced and are being phased-in throughout the state. The objectives of these regulations are to maintain crop productivity while also reducing environmental pollution due to the over-application of plant nutrients.

Fortunately, managing nutrients to optimize crop growth and water quality are not mutually exclusive. Applying the Right Amount of fertility, at the Right Time, to the Right Place, in the Right Form (4Rs) is likely to maximize the amount of fertilizer that is taken up by the crop and minimize the amount of fertilizer that is wasted or lost to the environment. Since the application of fertilizers is generally one of the highest input costs in agricultural systems, this approach saves farmers money while reducing their environmental footprint in surrounding bodies of water. However, such best management practices (BMP) tend to be highly specific to the crop and environment where they are applied. Further, they involve not only management of the nutrients themselves, but also the interaction of the nutrients with water that is added to the crop-soil system (whether via irrigation or rainfall). Therefore, BMP should be governed by a few fundamental principles, but adapted to the particular cropping context where they are applied. The objective of this practice page is to outline several of the key principles for managing nutrients to maintain water quality without sacrificing crop productivity. Also included are links to resources that will assist in better understanding and implementing BMP as well as links to case studies that exemplify context-specific applications of BMP.

SOURCE: The California Agricultural Water Stewardship Initiative

Nitrogen (N) makes up 78 percent of the air we breathe in the form of nitrogen gas (N₂), but this form is unable to be used by plants. In fact, there are 34,000 tons of N in the air above an acre of land, but none of it can be used by crops. Nitrogen must be fixed in order to become available, which is done through the process of making industrial fertilizers or through nitrogen-fixing bacteria associated with the roots of legumes. A significant amount of nitrogen occurs in the soil naturally (2,000–4,000 pounds per acre, lbs/A), but 98 percent of that nitrogen is in the organic form and also cannot be used by plants. This organic nitrogen is found in all living and previously living material in the soil. Nitrogen naturally becomes available in soil as organic matter is mineralized, which results in around 60–80 pounds of nitrogen per acre per year for crop uptake. Two forms of inorganic nitrogen are plant available: ammonium N (NH₄⁺) and nitrate N (NO₃^–). Ammonium N is held on the soil particles and can be exchanged with other cations in order for plants to take it up, but it does not leach easily from the soil. Nitrate N, on the other hand, is found in the soil solution and can be leached from the profile. Nitrogen leaching needs to be managed properly to ensure that plants have access to the nitrate and also to minimize the nitrate pollution in waterways. Understanding the nitrogen cycle thoroughly allows us to do that. The processes involved in the cycle are summarized below.

The forms of nitrogen, the transformations that it undergoes in the soil, and the nitrogen loss pathways are summarized in the N cycle (Figure 1). Most of the transformations in the N cycle are the result of microbial activity. Because these are biological processes, they are very sensitive to the environment where they occur. Major factors influencing these processes are temperature and moisture and thus the weather. The challenge with managing N is to achieve maximum N availability when crops need N and to reduce loss of N to the environment. The goal is to minimize soluble forms of N when at times of little or no crop uptake. This can be achieved by understanding the N cycle and managing inputs. The three main pathways of N loss are nitrate leaching, denitrification, and volatilization, discussed below.

Figure 1. Nitrogen cycle: Transformations between N forms.

SOURCE: Penn State Extension

A healthy lifestyle consists of a mixture of habits. Diet, exercise, sleep and other factors all must be in balance. Similarly, a sustainable farm operates on a balanced plan of soil, crop, and water management techniques.

Soil moisture sensors aid in advanced irrigation scheduling and help measure water consumption on farm fields. Photo credit: Matt Yost

The western United States is a region with scarce water resources. In this case, water management techniques make up a larger piece of a sustainability plan. There is mounting concern around the globe about water scarcity. This is due to urban sprawl, depleting water supplies in some areas, and predicted water shortages in the future with less snowpack.

Water management techniques that lead to the optimal use of limited resources are not well-identified. Yet. Matt Yost, a researcher at Utah State University, is working to find the best combination of practices to maximize yield, profit, and water efficiency.

“Most cropland in Utah and the western United States is irrigated,” explains Yost. “There are areas where groundwater from aquifers is being used faster than it can be replaced. Some of these areas are under intense pressure to conserve water.”

Water for irrigation comes from aquifers far below the farm’s surface. Aquifers are naturally refilled by water from the surface by precipitation. Increased water use can lower the water table. Eventually wells can go dry. These factors make water optimization crucial for food security.

Pivot technology trial in Central Utah. From left to right: low elevation spray application (LESA), mid-elevation spray application (MESA), and mobile drip irrigation (MDI). Photo credit: Matt Yost

Yost researches many water management techniques. These include using irrigation scheduling and advanced pivot irrigation technology. In addition, his team researches crop and soil management practices. They look at rotating in drought-tolerant crops, cover crops, and reduced tillage.

Yost’s team works together with many farmers across Utah to do farm-scale trials.

“Irrigation research is tough and costly on farmer’s fields,” says Yost. “It’s especially true when it comes to irrigation scheduling. Though difficult, this on-farm research and collaboration is crucial for the understanding and adoption of new water optimization techniques.”

So, what is the best combination of management techniques to maximize yield, profit, and water efficiency? The answer isn’t clear, yet. Results and analyses are still pending, but Yost offers some initial recommendations:

• Advanced pivot irrigation technologies, such as mobile drip and low-energy precision application or spray application, are beneficial. They can usually maintain crop yields with about 20% less applied water.
• Most farmers may be able to reduce irrigation rates by 10% without affecting crop yields.
• Biochar applications are showing few short-term crop yield or water saving benefits.

Advanced pivot irrigation systems such as mobile drip irrigation, low-energy precision application and low-energy spray application reduce wind drift and evaporation – allowing for reduced irrigation rates. Photo credit: Jonathan Holt

“We are beginning to answer questions about new irrigation techniques and scheduling approaches,” says Yost. “But many still exist for discovery.”

Next, Yost and his team hope to secure funding for long-term irrigation research sites. Water is a limited and vital resource. Strategies to optimize water use will be crucial to the sustainability of irrigated agriculture.

“In irrigated agriculture, agronomy and irrigation go hand-in-hand,” explains Yost. “Nearly everything about one influences the other. Most irrigation programs focus more on engineering than on irrigation science. With my original training in agronomy, I’ve noticed knowledge gaps and have identified opportunities to unite irrigation science and agronomy.” Yost’s unique perspective offers a holistic approach to integrated water, soil, and crop management.

SOURCE: Crop Science Society of America. Dec 2, 2019