Nutrient Management

INTRODUCTION

Nutrients, whether in fertilizer or other materials, are both an essential input and a major cost for crop production. In Ontario, commercial fertilizer and lime applied to cropland cost farmers almost $275-million annually. The manure from about 2-million cattle, 3-million hogs, and 37-million chickens and turkeys is also applied to cropland.
Some farmers apply nutrients in excess of recommended rates in hopes of attaining higher yields. This is not a best management practice if it ignores costs, profits, and environmental quality. Neither is it a best management practice to apply too few nutrients. Yield and profits will drop.

Livestock are an important part of the nutrient cycle in Ontario.	Growing crops with insufficient nutrients will lower yields and profits.

Over time, poor nutrient and soil management practices can impair your land's ability to produce crops.
Poor nutrient management can also be costly to the environment. Applying more nitrogen than the crop can use will increase the risk of nitrate-nitrogen leaching from the soil, thereby polluting precious ground water resources.

Nutrients must be managed wisely to preserve the quality of our soil, air, and water. Essential Nutrients from the Soil Macronutrients Symbol Nitrogen N Phosphorus P Potassium K Magnesium Mg Calcium Ca Sulphur S Micronutrients Zinc Zn Manganese Mn Boron B Iron Fe Copper Cu Molybdenum Mo Chlorine Cl Nickel Ni Cobalt Co

Runoff from snowmelt or heavy rains can carry nutrients such as phosphorus to streams, drains, and rivers. Eroding cropland can pollute surface waters with sediment and nutrients attached to soil particles. By adopting best management practices, you can do your part to reduce environmental risks. This booklet will help you plan and implement a nutrient management strategy to use nutrients profitably while protecting the environment. More specifically, Nutrient Management will help you increase your understanding of: the importance of nutrients to your crops the behaviour of nutrients in soil sources that add nutrients to soil factors that influence the supply of nutrients available to your crops the effects of poor nutrient management. This booklet also describes best management practices for: determining the amount of nutrients to apply applying nutrients. Throughout the booklet, we'll be referring you to other Best Management Practices booklets, especially Soil Management, Livestock and Poultry Waste Management, Water Management, Field Crop Production, and Horticultural Crops. We urge you to read these companion booklets: they'll help you see your nutrient program in the big picture of resource management on your farm.

WHAT ARE NUTRIENTS?

Plant nutrients are chemical elements, or simple compounds formed from them, needed by plants. The most common elements in plants are carbon, hydrogen, and oxygen, obtained from air and water. All other nutrients are available in soil.

Green plants convert light, water, air, and plant nutrients into forms useful to people and animals.

Six nutrients are required by crops in relatively large amounts. These are often referred to as macronutrients. The other nutrients are required in quite small amounts – often less than one kilogram per hectare per year. These are called micronutrients. Nutrients exist in either organic or inorganic (mineral) form. Organic compounds are produced by living organisms and contain carbon. Inorganic compounds result mainly from chemical reactions and do not contain carbon. For example, protein is an organic form of nitrogen; ammonium-nitrate is an inorganic or mineral form. Nutrients are naturally present in soil in inorganic forms, as the result of the weathering of soil minerals. Nutrients taken up by living organisms may be converted to organic forms to make up the bodies of plants, animals, and micro-organisms. Organic forms of nutrients in living organisms return to inorganic forms when these organisms die and decompose.

Nutrient and Soil Management: The Best Combination

Nutrients are essential for plant growth and reproduction, but they are only one of the essential inputs needed by crops. Take another look at your present soil management program: if it considers only the amount of nutrients available to crops, it's probably unsatisfactory. Bear in mind that your soil's ability to support plants and to supply water, oxygen, and heat to plants is also important. A lack of any one of these directly affects plant growth, and can impair your crop's ability to use nutrients present in the soil. For available nutrients to be used efficiently, soil must have good structure, proper drainage, and good moisture-holding capacity. See Best Management Practices booklets, Soil Management, Field Crop Production, and Horticultural Crops for more information. DEVELOPING A NUTRIENT MANAGEMENT SYSTEM Profitable, sustainable crop production depends on proper nutrient management. Your nutrient program should meet the following goals: satisfy crop nutrient requirements for profitable yield and quality minimize the risk of damage to the environment minimize the cost of supplying nutrients be practical and feasible with current resources use manure and other organic materials to best advantage. These goals are not incompatible. When all the nutrients available on your farm are used efficiently in meeting crop needs, the risk of damage to the environment (water quality in particular) should also be reduced.

Plants also take up nutrients that they don't need, but animals do: Iodine I Chromium Cr Sodium Na Selenium Se Crops cannot obtain sufficient nutrients from soil that is in poor physical condition. NUTRIENT MANAGEMENT AFFECTS CROP: Growth Maturity Reproduction Harvestability Insect Tolerance Disease Tolerance Winter Survival Profitability Standability Quality Yield

Meeting Crop Nutrient Requirements

When developing a nutrient management system, keep in mind the needs of all of the crops in your rotation.
Here are some reminders about yield, quality, and nutrients:

• final yields are not determined by fertility alone: remember soil management, climate, plant population, timing, pest and weed management, and variety selection
• some high-value crops have unique fertility requirements for quality, e.g. boron in rutabagas and potassium in tomatoes
• some legume crops provide some nitrogen for crops in following years – plan for and estimate the amount
• it may not be desirable to supply all of a crop's requirements from organic sources (manures, sludges, legumes, etc.), as some nutrients may be oversupplied
• you need to know fertility levels and crop requirements to apply appropriate rates
• timing is everything – if a crop can access nutrients when needed, quality and yields are higher
• the maximum yield that you can obtain will usually not be your most profitable yield.

Nutrient Deficiencies

No nutrient is more important than another – all are essential. The majority of soils can supply most nutrients to most crops. Generally, a nutrient management program is only concerned with nitrogen, phosphorus, and potassium. However, deficiencies of other nutrients do occur. Some soil types are prone to deficiencies of certain nutrients, because of the way in which the soils were formed. Similarly, some crops have a higher requirement for specific nutrients than do other crops. The chart on page 21 lists the nutrient deficiencies most commonly encountered in Ontario and the situations in which they are most likely to be a problem. For more information on nutrient deficiencies, see "Nutrients in the Soil and in Plants", page 17.

The lack of a nutrient can limit crop growth and quality.

 

Nutrient Toxicities

If available at excessive levels, some nutrients are potentially toxic to plants. For example, the margin between boron deficiency and toxicity is quite narrow, and varies among crops. Cole crops and alfalfa have relatively high requirements for boron. In the year following application, however, boron applied for cole crops can cause damage to sensitive crops such as soybeans, field beans, and cereal grains.
For more information on nutrient toxicities, refer to "Nutrients in the Soil and in Plants", page 17.

Minimizing Costs of Applying Nutrients

A well-planned nutrient management system can save you money in many ways. Putting one together will help you:

• save time and money by purchasing and applying only what's needed
• make better use of on-farm nutrients
• identify opportunities for using lower-cost alternative sources of nutrients, e.g. manure from a neighbouring farm, sewage sludge, other forms of commercial fertilizers
• consider more efficient fertilizer application practices
• use rotations, cover crops, residue management, and sound soil management practices to conserve the nutrients in the soil.

Keeping It Practical

Be practical and work within existing resources: make sure the changes fit the rest of your crop production system use local sources of nutrients and equipment whenever possible cooperate with neighbours and dealers for special equipment needs.
	Keep it practical – use existing equipment whenever possible.

Nutrients and the Environment

Nutrients can pollute water. Nitrate-nitrogen can leach into ground waters. Phosphates can run off land to surface waters such as drainage ditches, streams, and rivers. Concentrations of these nutrients in water above tolerable limits are harmful to humans, livestock, and wildlife. Agriculture is one of the sources of nutrient pollution in rural areas.

Phosphorus and Water Quality

In unpolluted waters, growth of aquatic plants, including algae, is limited by the low level of phosphorus. When phosphorus is added to water, more plants are able to grow.
In recent decades, abundant plant growth has made the water in many lakes and rivers in Ontario unsuitable for drinking or swimming. Excessive plant growth has also led to the death of fish and other aquatic animals from lack of oxygen in the water. (Oxygen is used by plants for respiration and by micro-organisms in breaking down plants after they die.)
Phosphorus is a major pollutant in the Great Lakes–St. Lawrence River watershed.

Phosphorus pollution comes from many sources in urban areas, mainly sewage treatment plants, storm sewers, and industrial sources. Most of these are point sources (i.e. easy to locate). In rural areas, the sources are sewage treatments from small towns, improper septic systems, storm sewers, manure runoff, nutrient runoff, milkhouse wastes, and eroded soil. Most of these are non-point sources (i.e. harder to pinpoint). Phosphorus from farmland has three sources: the farmstead pastures near watercourses cropland.

High phosphorus levels in water allow excess growth of aquatic plants

PHOSPHORUS POLLUTION SOURCES IN RURAL AREAS

	A 1986 study compared county fertilizer sales data with provincial soil test recommendations. It estimated that fertilizer application rates exceeded recommended rates in several Lake Erie counties.
Rural surface waters can also be polluted by runoff (soil particles and attached phosphates) from croplands.

Some phosphates and other pollutants are discharged to rivers from sewage treatment centres in small towns.	Waste washwater containing phosphate-based detergents from some dairy farms reaches surface waters through direct hookups to tile lines.

Illegal or improper hookups from septic systems can deposit phosphates and nitrate directly into ditches, streams, and rivers.	Manure can run overland or through tile drains to contaminate surface waters. This is especially true if your pastures or yard areas are located near watercourses.

The risk of contaminating surface water is increased when nutrients are applied in excess of recommended rates. This is of particular concern when soils are in the High (H), Very High (VH), or Excessive (E) fertility ratings of phosphorus. The Best Management Practices booklets, Livestock and Poultry Waste Management, Water Management, Field Crop Production and Horticultural Crops also have information to help you minimize the risk of phosphorus pollution.

Phosphorus pollution has contributed to the regular closings of rural beaches. Results from the Fanshawe Reservoir Clean Up Rural Beaches study shown above indicate the relative annual contributions of total phosphorus.

Nitrogen and Water Quality

STANDARDS FOR NITRATE- NITROGEN LEVELS IN WATER Intended Use Acceptable Concentration LIVESTOCK* 100 mg/L HUMANS 10 mg/L * producer experience suggests that the nitrate level in water for white veal calves should be similar to that for humans. A survey conducted in 1992 of 1,300 rural wells in Ontario found 15% with unacceptable levels of nitrate. In the same survey, ground water quality was tested in cropped fields adjacent to 141 of the wells. Of these sampled sites, 21% had an average level of nitrate that was unacceptable.

Nitrogen, in the nitrate form (NO3), can be leached from the soil into ground water. The amount of nitrate that's leached depends on: the amount of water draining through the soil the amount of nitrate-nitrogen in the soil the type of soil materials sandy and gravelly soils are more prone to leaching, as are soils that are shallow to bedrock. (This is compounded when soils have a naturally high water table.) Excess nitrate-nitrogen in the soil – from fertilizer, livestock manures, or legume plowdown crops – can make ground water unsafe to drink, especially for infants, the elderly, and young animals. Nitrate will also enter surface water through tile drainage systems. Nitrogen, in the ammonia form (NH3), is very toxic to fish. Contamination of watercourses with materials containing large amounts of ammonia, such as liquid manure, can kill large numbers of fish.

There are three main sources of nitrogen pollution in rural areas: faulty septic systems nitrate from household and human wastes can contaminate ground and surface waters livestock wastes bacteria, nitrate, and ammonium-nitrogen from improperly handled, stored, or applied manure can run off to surface water or infiltrate soils and leach to ground water resources cropland some of the nitrate from commercial fertilizers and manures can run off to surface water or leach into ground water crop residues. Ground water contamination by nitrate needs more research to determine the effect of nutrient management practices and site conditions.

Nitrate-nitrogen leached from soil can make drinking water unsafe.

Energy Use

Much of the cost of supplying nutrients stems from the energy required to manufacture, refine, transport, or apply them. Efficient use of nutrients helps reduce both the cost of crop production and the consumption of non-renewable resources.

Making a Nutrient Management Program Work

Nutrient management programs are often viewed on a field-by-field basis. This ensures that each field can supply the nutrients needed by the crops to be grown there. However, in planning a nutrient management program, you must consider the production system of your entire farm. The method you choose to supply nutrients can have an impact on other farm operations. Similarly, changes in other farm operations (e.g. tillage) can affect the way in which nutrients must be managed. Take all factors into account before making a change. Unless you're deliberately building up or drawing down the level of nutrients in specific fields, the amount of nutrients on your farm will remain about constant over time.

Consider all factors affecting the nutrient balance on your farm in your management program.

Source: Our Land and Its Care, The Fertilizer Institute.