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Water Today Title November 20, 2017

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Agriculture and Water


While it uses only 7% of Canada’s total land area, agriculture plays a major role in Canada’s economy. According to Statistics Canada 2011 Census, there are a total of 205, 730 farms in Canada, the sector provides one in eight jobs, employing over 2.3 million people, and accounts for 6.6% of Canada's gross domestic product (GDP).

As a point of comparison, in 2015 the Natural Resources Sector - Forestry, fishing, mining, quarrying, oil and gas - accounted for 1.77 million jobs in Canada and for 17 % of the national GDP.

The structure of agriculture has however dramatically changed over the last decades, seeing the number of farms and farmers decrease while the size of farms and the age of farmers increased. Agriculture and Agri-Food Canada (AAFC) anticipates that these trends will hold true in the years to come and that more consolidations will take place leading to less and larger farms.

    While there were 280,043 farms in 1991, that number had gradually declined to 205,730. Since 1991, the average farm area increased from 598 to 778 acres, while the number of farm operators decreased from 390,875 to 293,925, a 24.8% drop. Over the same period, the average age of farm operators increased, rising from 47.5 to 54.0 years. The trends of fewer operators and fewer farms show no signs of reversing and could indicate significant turnover in farm assets in the future. As the number of younger farmers continues to shrink, it is also reasonable to expect that significant amounts of farm assets will be bought by remaining farmers (increasing the number of larger farms) or may also be purchased by beginning farmers, private investors and immigrant farmers. - Statistics Canada

Agriculture is also the largest consumer of water and one of its major polluters. As early as 1994, US-EPA identified agriculture as the leading cause of water quality impairment of rivers and lakes in the United States , a situation which is replicated in Canada and around the world.
    The agricultural sector is by far the biggest user of freshwater. In Africa and Asia, an estimated 85-90% of all freshwater used is for agriculture. According to estimates for the year 2000, agriculture accounted for 67% of the world's total freshwater withdrawal, and 86% of its consumption. We use the water to irrigate crops and although a large percentage of the water returns from the fields, often it has been changed and is carrying soil and dissolved compounds.

    “While agriculture is not the only activity with the potential to affect freshwater negatively, it is a very important one. There may be surface runoff of pesticides, fertilizers and manure, or leaching of nitrogen into groundwater, the fate of which is discharge to surface water bodies. This means dissolved contaminants will eventually find their way into lakes, rivers or the ocean. Other activities that present risks to water include manufacturing, forestry, mining, waste disposal and runoff from urban areas." - AAFC

One of the major water quality issues is caused by high nutrient loads resulting from fertilizer overuse, particularly phosphorus which has resulted in the proliferation of algal blooms across Canada’s lakes and rivers, negatively affecting ecosystems, drinking water, and recreation.

The issue gained international attention in 2015 when the largest bloom of this century was recorded in Lake Erie, culminating in a city-wide Do Not Consume Advisory effecting 400,000 people in Toledo, OH and leading to a US-Canada agreement to reduce phosphorous by 40 percent to improve Lake Erie water quality, signed in February 2016. The widespread use of pesticides also poses a serious risk to our ecosystems. According to the Food and Agriculture Organization of the United Nations (FAO)
    The term "pesticide" is a composite term that includes all chemicals that are used to kill or control pests. In agriculture, this includes herbicides (weeds), insecticides (insects), fungicides (fungi), nematocides (nematodes), and rodenticides (vertebrate poisons).

    The use of pesticides coincides with the "chemical age" which has transformed society since the 1950s. In areas where intensive monoculture is practiced, pesticides were used as a standard method for pest control. Unfortunately, with the benefits of chemistry have also come disbenefits, some so serious that they now threaten the long-term survival of major ecosystems by disruption of predator-prey relationships and loss of biodiversity. Also, pesticides can have significant human health consequences.

The fact that many of Canada’s rivers and lakes are shared with the United States further exacerbates the agriculture/ water pollution nexus in Canada. There are no regulations in the US regarding water and measures to combat water deterioration are voluntary.

A 2014 Congressional Research Paper states: “Traditionally, farm and ranch operations have been exempt or excluded from many federal environmental statutes and regulations, and some point out that the relative number of environmental regulations affecting agriculture is small compared to other industries… Therefore, the current federal farm policy addressing environmental concerns is in large part voluntary; that is, it seeks to encourage agricultural producers to adopt conservation practices through economic incentives… While many of these voluntary programs and policies have been in place for decades and have had considerable success, some question whether a strictly voluntary approach to agricultural conservation generates sufficient environmental gains."

Recent efforts by the US EPA to regulate the agricultural sector have not been well received by many agricultural industry groups, many of whom have been vocal in their displeasure, claiming EPA is “overreaching" its regulatory authority.

There are many ways to manage agriculture’s relationship with water to increase its efficient use and enhance environmental protection. Best Management Practices (BMPs) - practical ways to ensure that risks to the environment are minimized without sacrificing economic productivity - technological innovations, governance strategies, and policy tools are some of the ways in which this can be accomplished.

It is part of Agriculture and Agri-Food Canada’s mandate to “work with provinces, territories, and other willing partners, to help the sector adjust to climate change and better address water and soil conservation and development issues." With a view to accomplishing this goal, AAFC is helped by an extensive team of scientists working in twenty Research Centres across the country.

For the purpose of this article, we approached three scientists working on specific research: Dr. Dan Reynolds, Managing Soils to Benefit Crops; Larry Braul, Water Quality Engineer, Limiting Contamination from Pesticide Spills; and Dr. Barbara Cade-Menun, Long-term Study of Legacy Phosphorus. A brief overview of each research project and an email interview with the scientists who worked on them follows.

Managing Soils to Benefit Crops
The first project Managing Soils to Benefit Crops aims to increase field crop yields and reduce soil and environmental damage with management practices suitable for all soil types. Headed by Dr. Dan Reynolds, working in collaboration with Ontario Soil and Crop Improvement Association (OSCIA), the research examined soil physical quality and resilience in two studies.

In the first study, in 2013, eighty intact soil core samples were collected and assessed for air capacity, plant-available water capacity, organic carbon content, and dry bulk density. These physical capacities indicate a soil's ability to store root-essential air and water, the amount of organic matter sequestered in the soil, and soil hardness or compaction. A second study in 2014, involved weekly field measurements of soil water content to assess soil resilience to heavy rains and drought conditions.

The research confirmed, among other discoveries, that organic amendments, multi-crop rotations, and cover cropping can improve the physical quality and resilience of virtually any soil; and that determining a soil's plant-available air and water capacities and monitoring root zone moisture content can provide early detection of onset of waterlogging and drought stresses, and improve irrigation scheduling of high-value horticultural crops.

Q&A Dr. Dan Reynolds
Watertoday - You state, "the combination of rotating crops, adding amendments and planting cover crops in the fall can improve the physical quality and resilience of soil. Can you explain what amendments and cover crops are?

Reynolds - Amendments" are essentially anything one adds to the primary crop root zone (top 15-30 cm of soil) to improve crop productivity. Examples of common amendments include commercial fertilizers, livestock manures, composts, lime (for pH reduction), gypsum (to improve soil aggregation), and various “green manures" which are usually cereal crops (e.g. rye, oat, wheat) grown briefly in the fall or spring and then plowed down before the main crop is planted.

“Cover crops" are crops that are planted in the fall after harvest of the main crop (e.g. corn), or in the late spring between the rows of the main crop (e.g. corn). The main purpose of cover crops is to protect exposed soil from wind and water erosion during the non-cropping (over-winter) period after the main crop has been harvested. A secondary purpose of cover crops is to “scavenge" or “collect" crop nutrients that were left-over in the root zone after harvest of the main crop, and thereby prevent these left-over nutrients from leaching into tile drainage water or ground water during the non-cropping (over-winter) period. The cover crops are then plowed down or chemically killed in the spring before planting the main crop, which causes the cover crops to gradually release their stored nutrients for use by the main crop. Common cover crops for Southern Ontario include red clover, crimson clover and hairy vetch.

Watertoday - Does the research you're doing on soil take into account different fertilizers?

Reynolds - Most of the amendments and cover crops mentioned above improve crop productivity by increasing both soil fertility and soil quality/resilience.

Watertoday - It seems to present that the research is done on "intact soil core samples', was this on purpose?

Reynolds - Yes. The soil parameters we need to measure (i.e. parameters quantifying water/air storage capacity) are best done in the laboratory using intact soil core samples collected from the fields being examined.

Watertoday - When you say different soils have different percentages of water/air absorbency, it's not clear from what I can see that there is an end to this research. What ideally would be the end run of this research?

Reynolds - The objective of this research was to measure the amounts of crop-available water and air the soils at the various field sites can retain, and compare these values to “optimal" or “preferred" values established in the scientific literature. This comparison can then be used to determine if the soils need (or could benefit from) improvement with respect to water/air storage capabilities. The ultimate goal is to maximize the soil’s ability to store crop-available water and air, and thereby increase the soil’s resilience to water excesses (waterlogging) and deficits (droughts).

Watertoday - Study 1 examined samples for air capacity, plant-available water capacity, organic carbon content, and dry bulk density, concluding that all 10 soils tested 'had insufficient organic carbon and excess bulk density for optimal field crop production'. Can you briefly explain in layperson's terms what this essentially means and how the different deficiencies can be remediated?

Reynolds - Insufficient organic carbon (or insufficient organic matter) and excess bulk density (or excess soil hardness) essentially means that the soil’s natural fertility and ability to store crop-available water and air are below their ideal or preferred levels. Ways in which these deficiencies can be remedied (at least partially) include application of organic amendments (e.g. composts, green manures) and use of cover crops.

Watertoday - Study 2 states that medium textured loam soils have the best combination of air and water capacity for field crop production, You say, 'Both coarse- and fine-textured soils tend to have lower physical quality and lower resilience than medium-textured soils'. What measures can be taken to alleviate this?

Reynolds - At present, improving the physical quality and resilience of coarse- and fine- textured soils mainly involves application of amendments and use of cover cropping. Essentially one needs to increase the storage capacity of plant-available water in coarse soils (by, for example, increasing organic matter levels through addition of organic amendments), and increase the storage capacity of plant-available air in fine-textured soils (by, for example, increasing soil structure through proliferation of cover crop roots).

Watertoday - How is the knowledge gathered from these studies transferred to the farming community? Do you work with farm groups? And lastly, does your know-how benefit other countries as well? is that part of your mandate? I'm thinking of Sudan, Kenya where they seem to be overwhelmed with growing issues.

Reynolds - This work was done in collaboration with Ontario Soil and Crop Improvement Association (OSCIA), who interface directly with farm groups. Yes, this work will potentially benefit agricultural production in other countries.

Watertoday - With more and more of our population moving into urban areas, how is all of the knowledge gathered in this space get protected, passed on to new farmers? After talking to farmers at various conferences, it's clear that they (the old farmers) are worried about succession on the farm, the know-how the labour force and the advent of multi national farm consortiums.

Reynolds - Accrued knowledge is “protected" through publication of reports and scientific articles, and it is passed on to farmers through producer groups (e.g. OSCIA), the Knowledge and Technology Transfer (KTT) division of AAFC, provincial extension groups (e.g. OMAFRA), and university extension activities (e.g. University of Guelph).

Long-term Study of Legacy Phosphorus
Phosphorus is a chemical element essential for life. Without adequate phosphorus, plant growth and crop yield are reduced. However, fertilizer phosphorus added beyond the crop’s yearly needs can remain in the soil, and can become more tightly bound to soil than recently added fertilizer. Because it is more tightly bound, it may not show up in “soil test phosphorus" analyses that measure readily available soil inorganic phosphorus to determine fertilizer requirements. So researchers at Agriculture and Agri-Food Canada (AAFC) are investigating legacy phosphorus in studies at various locations across Canada, through a phosphorus project led by Dr. Noura Ziadi at AAFC-Ste. Foy.

One study in this phosphorus project is led by Dr. Barbara Cade-Menun at the Semiarid Prairie Agricultural Research Centre (SPARC) in Swift Current, Saskatchewan. Her team is studying a set of agricultural plots that were established in 1967. Until 1995 these plots received both phosphorus and nitrogen fertilizer, but then each was split in two so that phosphorus treatments could be stopped on one half of each plot. The result is a long-term, controlled study of legacy phosphorus.

What has surprised the researchers is the growth of the wheat plants on the plots not fertilized by phosphorus: although tests showed very low concentrations of soil test phosphorus on the no-phosphorus plots, there was no difference in yield, or in grain phosphorus concentration as compared to the fertilized plot.

While this research will need to be replicated with other crops in other soil and environmental conditions, it suggests that farmers might be able to change the way they think about phosphorus fertilizer. Accessing existing phosphorous from the soil would be a cost saving for the farmer and potentially reduce the risk of phosphorus loss into nearby water bodies.

Q&A - Dr. Barbara Cade-Menun
Watertoday - The report says that legacy phosphorus may not show up in “soil test phosphorus" analyses done to determine the level of fertilizer needed. Are these soil tests always performed in the farming community or is the same amount of fertilizer always applied? Can you explain 'tightly bound'?

Cade-Menun - The measures of soil test phosphorus that we used are common soil tests in Canada. It is generally advised that farmers conduct soil testing regularly, and most do. Some farmers conduct soil testing every year, some every few years; it varies with location, crop and producer. Some apply the same amount of fertilizer every year without soil testing, based on what is estimated in crop removal.

In soil, phosphorus is bound to soil mineral particles and needs to be moved into the soil solution (the liquid between the soil particles) for roots to take it up. Loosely bound phosphorus moves readily from the soil particles to the soil solution, usually just to maintain soil solution concentrations in response to plant uptake. Tightly bound P doesn’t move as easily into the soil solution. It usually requires something else to release it to the soil solution, such as the production of organic acids or enzymes by plants and microbes.

Watertoday - The project timeline was 1995 2010: Have any other locations, crops been tested since?.

Cade-Menun - I haven’t tested any other locations specifically in Canada with these methods with and without P fertilization, but have been involved in other studies in other locations (China, Idaho, Ireland). And other scientists are using these methods in other locations in Canada and elsewhere. The timeline of that study was 1995 and 2010 because the plots were converted to stop applying P in 1995, although the plots were originally established in 1967. We have archived soil samples back to 1995, but nothing older than that. .

The plot treatments themselves have continued since then, so we have more recent results. However, we haven’t analyzed everything with these advanced methods as yet. For that project, we just looked at the continuous wheat rotation. However, we have other rotations and crops for those plots and are working on analyzing those too. The advanced methods (NMR, P-XANES) are expensive to use and time-consuming, so we will probably not be able to analyze everything. We are currently working with the soil microbiologist here to try to understand more about how the plants are getting P from the plots with no fertilizers, testing enzyme and organic acid production among other things..

Watertoday -The results in the Saskatchewan area were compelling, has this concept been adopted by farmers in the area?.

Cade-Menun - The producers here are interested in the results. However, we all recognize that crops here in this part of Saskatchewan are limited by water first and nitrogen second, and then maybe P depending on past land management and fertilizaton. There is also recognition that these were done on small plots at the research station. So I’m not sure how widely this has been adopted..

Watertoday - Is there interest in the farming communities in opting for best management practices or is it a battle?.

Cade-Menun - I have only worked here since 2008, so don’t have too many years of experience. However, the producers I have worked with throughout the province have all been interested in finding the best management practices and using them when the scientific results are clear. .

Watertoday - What was the role of the Canadian Light Source in this project?.

Cade-Menun - The P-XANES work was done at the Canadian Light Source.

Limiting Contamination from Pesticide Spills, Splashes and Rinses

Pesticides are commonly used on most traditional farms around the world to control harmful insects and weeds. While farmers take great care in using pesticides, runoff from mixing and rinsing locations has become an area of environmental focus as up to 80 percent of contaminants found in water bodies trace back to on-farm activities. Europe has been using a system called a biobed to capture and degrade the unintentional release of pesticides into the environment.

Larry Braul, Water Quality Engineer, AAFC Regina, and Dr. Claudia Sheedy, Research Scientist, AAFC Lethbridge, are co-leading a project to develop a biobed model to support Canadian farmers.

Key findings in this research project indicate that a biobed, used to absorb and degrade pesticides from sprayer rinsate, can be a very effective tool for reducing a significant source of on-farm pesticide contamination.

Q&A - Larry Braul, Water Quality Engineer

Watertoday - AAFC does not provide a timeline for this project? When was it started? Is it still ongoing?

Braul - Background research was completed by Tom Wolf between 2007 and 2010. The present project runs from 2013 to 2017.

Watertoday - The report says that up to 80 percent of contaminants found in water bodies trace back to on-farm activities, does this refer to pesticides only?

Braul - We are talking about pesticides.

Watertoday - Can you explain how biobeds actually break down pesticides?

Braul - It is a complex process but to simplify it, the organic matter absorbs the pesticides and microbes (fungi or bacteria) use pesticides as an energy or nutrient source thereby degrading the structure of the pesticides. Would this work with all pesticides? This process works to some extent for all pesticides but better for some pesticides than others. Overall we have removed over 98% of the pesticides with the double celled biobed in each of the last two years.

Watertoday - Has a solution been found to keeping the beds warm in Canada? Have both electrical and solar solutions been tried?

Braul - We have tested both electrical and solar solutions and both work well. As microbes are much more active in warmer temperatures, we expect a significant benefit for heated biobeds.

Watertoday -Has this experiment been tried in other locations?

Braul - Biobeds are common and successful in Europe and South America. They do not use a heating source in these locations.

Watertoday -Has there been other developments?

Braul - Researchers are working on determining the best temperature range for efficient pesticide removal, developing options for reuse of the effluent, determining the benefit of addition of nutrient and inoculants (microbes found to be prevalent in biobeds) to accelerate decomposition and studying degraded compounds (metabolites). We will be producing a construction, operation and maintenance manual for pesticide biobeds in 2017.

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