Unit 2 - Agricultural Production, Pollutants, and BMP

Population growth is the _______.

largest factor for food demand

• More people = more demand for food production

97% of world’s population increase is in ______.

Asia, Africa, and Latin America

• Food supply problems in fast growing areas

Factors influencing Food Demand

• population growth

• increased wealth/incomes

Higher incomes means _______ .

increased demand for higher quality foods such as meats and dairy products

• More energy to produce animal meat, loss of energy as you go up food chain

• 1 lb of chicken requires 2 lbs of grain, 1 lb of beef requires 7 lbs of grain

• 40% of world grain production goes into livestock feed

Definition of Hunger in reference to the Basal Metabolic Rate (BMR)

Minimum amount of energy to power human body maintenance, not including energy for activity

• Under 1.2 BMR food intake/day is undernourished

• 840 million undernourished worldwide

• Most of world’s hungry live in southeast Asia, Africa (south of Sahara) and Andean region of South America

Causes of Hunger

Uneven distribution of food and poverty

Uneven distribution of food

• Global food production from farms, ranches and fisheries is enough to provide world’s population with 3,800 calories/day

• Countries with limited natural resources / technology for food production face widening gap between food needs and food production – rely on imports

• High-quality diets are less energy efficient:

- If all grains were rationed across countries evenly, without any livestock feed diversions, it would feed 6+ billion

- Diet with 15% animal products, rationed evenly would feed 4 billion

- Diet with 30% animal products would feed 2 billion

Uneven distribution of poverty

• Poverty – wealthy eat relatively well in all countries, poor do not

• Over 1 billion people live in absolute poverty, 2 billion more near poverty

• Increases in food supply will not mean much if there are not various social and economic improvements to increase their (poor) ability to purchase food

Prospects for reducing world hunger → more land where?

• By the 1950’s most of the better crop land was already in cultivation

• Marginal farmable land was cleared, ditched, drained, modified for increased crop production

• Since mid 1960’s total global acreage devoted to agriculture increased by only 8%, but population increased by 100+%, most in developing countries

• Finite supply of good farmland

• Production increases in 1970’s and 1980’s due to intensive management of marginal lands → helped fill the gap for land and population demands - Heavily subsidized irrigation (government financial support that lowers the cost of water and irrigation infrastructure) - not sustainable - depleting streams and aquifers

Prospects for reducing world hunger → agricultural production increase?

South America and Africa

• Good undeveloped land for agriculture

• Lack transportation infrastructure (Roads, Railways, Ports) to get products to markets

• No close markets

• Two most populous nations (China and India), no good farmland left

Loss of good farmland

• Urban development

• Erosion

• Desertification = land becomes desert-like due to water not being managed correctly

• Salinization = sea level rise & irrigation water adding salt content to soil

Prospects for reducing world hunger → Yield increases?

• Improving yield per acre

• Corn yields on farms quadrupled from 1940-1985 in US

1. Mechanized equipment

2. Soil conservation practices

3. Fertilizers

• Wheat, rice, barley, rye, peanuts and sorghum also increased

• Great Britan tripled wheat production from 1940-1984.

• Plant breeding, seed stock, fertilizers, equipment, herbicides (kill weeds), pesticides, etc.,

• Yield ceiling- no more gains/acre (you can only get so much from the land)

• Environmental impact of unused (by crops) fertilizers, chemicals → runoff containing these chemicals

Methods for Reducing Post-Harvest Food Losses

• Better methods of handling and protecting food between harvest and consumer plates → Much lost to rats, birds, insects and molds

• Refrigeration and better storage containers

• Discarding imperfectly looking food → 95 billion pounds of food thrown out /yr

• Eating Lower on the Food Chain

1. Eat corn, wheat, oats, not beef

2. Could increase food supply 20-30%

3. Not going to happen, meat production in developing countries now exceeds industrialized countries

The plant essential nutrients hydrogen, oxygen, and carbon come _________.

from the atmosphere

Primary macronutrients

Needed in relatively large amounts for crop growth

• nitrogen, phosphorus, and potassium (the big three → typically what limits crop yields)

Secondary Macronutrients

Needed in relatively large amounts for crop growth but are required in smaller amounts than primary nutrients

• calcium, magnesium, and sulfur

Factors Affecting Nutrient Use Efficiency

• Climate, precipitation, temperature (frost) etc.,

• Soil type - influences water movements and soil retention - sandy (not a lot of plant available water), clayey and organic both hold more soil moisture

• Crop type and variety - corn, soybeans, etc.,

• Nutrient application

- rate, timing, placement, source

• Cultural practices - standard tillage, rip, conservation tillage (minimizes soil disturbance), no-till (no soil disturbance)

Cation Exchange Capacity (CEC)

Sum of exchangeable cations that a soil can adsorb (cmol/Kg). Typically increases with increasing clay and organic matter content.

• Most soils’ have a slight negative charge → cations stick to soil particles

Nutrient Retention and Mobility

• cations will be held in the soil

• anions cannot stick to the soil surface (like charges repel) and are highly mobile

Soil pH

• Changes in pH affect nutrient availability → a neutral pH and slightly acidic pH maximizes the availability of the majority of essential nutrients

• Can limit root growth under extremely acidic conditions

• Can affect the microbial population in the soil

Pollutants in NC’s Surface waters

• Sediment → soil particles that wash off → consider the worst water pollutant by the EPA

• Nutrients → Phosphorus and nitrogen

• Bacteria → Potential bacteria that cause diseases

• Pesticides

• Low Dissolved Oxygen → Oxygen levels too low to support aquatic life

In Freshwater systems (ponds, lakes, streams), _______.

Phosphorus causes algae blooms

• Levels of phosphorus are as little as 0.03 ppm

In Saltwater systems (estuary, sounds) _______.

Nitrogen causes algae blooms

• Levels of nitrogen causing blooms are 0.1 to 1 ppm

Nitrogen

• Generally the most limiting nutrient for plant growth → needed in high quantities for plants

• 78% of all nitrogen is gas and unavailable to plants

• Ammonia (NH3) and nitrate (NO3-) are nitrogen sources for the soil

Volatilization of N

Loss of applied N fertilizer to the atmosphere- NH3 via atmospheric

deposition downwind of source, can cause contribute significant amounts

of N to surface waters

Nitrification

• Changing Ammonium to Nitrate

• Nitrate is an anion (negatively charged) and very mobile in most soils.

  It can leach into the groundwater system, move with GW and discharge

  Into surface waters. Nitrification requires aerobic conditions.

Immobilization/Plant Uptake

Incorporation of NH4 and/or NO3 into plants, microorganisms

Soil organic material

Nitrogen in organic matter that is bound/mixed in with mineral soil

Nitrate Loss to Drainage Waters from Cultivated N.C. Coastal Plain Soils

• moderately drained soils = loose more pounds of N per acre per year due to higher infiltration rates than poorly drained soils (N will actually get to plants)

Surface Runoff vs Subsurface Leaching Nitrogen Losses

Most nitrogen is transported to surface waters via subsurface flow (groundwater system) in the NO3-N form. Some organic matter may attach to sediment and

can be delivered to surface waters via erosion and overland flow.

• most loss is due to GW leeching not surface runoff

Differences in land-use and soil types can _________.

influence the amount of nitrate in GW

Phosphorus moves ________.

differently than nitrogen

How much phosphorus is lost depends on?

• Crop

• Tillage

• Slope

• Soil Texture

• Soil Test P = how much P is in soil to begin with

• Type of Applied P

• BMPs that limit loss

• Rainfall

Phosphorus movement

• P will sorb/temporarily stick to the soil → extracted by plants (diffused from high to low concentrations)

• P is mainly lost through overland flow (runoff)

• Practices that reduce erosion reduces P-attached sediment loss

• If all exchange sites in the soil are filled with P → will just leech through

• Soluble P → was sticking to an iron oxide → oxidized → releases P

• Water and sometimes P will move → goes through GW system

Soil Test Interpretation

When the PI exceeds 50 → no need to add more → will give no yield increase

Phosphorus

• loss Primarily overland (surface)

• Attached to soil

• Soluble forms

• Sometimes leaches when phosphorus levels are very high

Nitrogen

• Primarily leaches (subsurface)

- Nitrate-nitrogen → anion → repels soil particles → lost

• Sometimes flows overland (Mostly as organic nitrogen)

Water Erosion

Natural process of soil movement from higher areas to lower areas by action of water flowing downhill.

• When precipitation rates are greater than infiltration rates, overland flow occurs, Increasing potential for erosion.

• Activities which result in loss of vegetative cover over soil and disturbance of soil surface increase risk of erosion.

• Steep slopes, high runoff velocities also increase risk of erosion

Water erosion results from:

1)Detachment- soil detached when rain drops impact exposed soil

2)Transport- flowing water carries soil particles

3)Deposition – water velocity slows and soil particles settle

Sediment

A major water quality problem – EPA says the greatest pollutant in U.S.

• Prevents light penetration (increases turbidity)

• Coats aquatic vegetation

• Clogs fish gills

• Deposition can reduce reservoir life and for navigable channels dredging may be necessary

• Many chemical species sorb (heavy metals, phosphorous, etc) to sediment and are often transported with sediment.

BMPs for erosion

• Grassed waterway = water hits the grass → grass holds the bank in place

• Sediment basin = sediment will fall out in basin (traps it before it leaves the farm; placed in the lowest part of the farm)

• Conservation Tilling = during the off-season leave up old crops

• Riprarian Buffer and Fencing = Used to keep cows and livestock out of waterways → will eat the vegetation along the banks and their hooves can disrupt the soil

Agricultural Best Management Practices reduce transport of pollutants to surface and Groundwater by:

1) Minimizing availability of pollutants

2) Slowing the transport and/or delivery of the pollutant

3) Remediating or intercepting the pollutant before or after it is delivered to the water resource through chemical or biological transformation

Where Do Agricultural BMPs Control Nutrient and Sediment?

• At the source → nutrient management

• During transport → cover crops and controlled drainage

• At the water’s edge or in the water → buffers and controlled drainage

Nutrient Management

Development, implementation and periodic maintenance of a plan to apply nutrients at rates necessary to:

• Achieve realistic crop yields = only put a fertilizer amount that matches the crop yields

• Improve timing of nutrient applications = only put fertilizer out when crops need it during their life cycle

• Increase nutrient use efficiency (reducing susceptibility to loss)

Main elements of Nutrient Management

1. Source - fertilizers, manure, Legumes (often use as a fertilizer source for the next crop as it can take N2 from the atmosphere), etc.

2. Timing - apply in accordance with crop needs

3. Placement - availability, uptake, loss potent.

4. Amounts - soil potential (RYE - Realistic Yield Expectations and N factor)

For nutrient management, site assessment and Recommended Site Specific Practices ________.

vary by the site

Published soil surveys are a part of _______.

nutrient management plans

• include aerial photographs with overlays of the different

  soil series in the area

• Help understand soil types of the land

• Provide important information about soil properties such as depth to water table, permeability, and texture.

• Great resources for many different applications concerning

land use.

For a Nitrogen management plan, the LBS. N per acre is determined by:

RYE (Realistic Yield Expectations) x N Factor

Cover Crops

Planted after harvest → Uptake left over from previous crops and prevent loss during typical fallow periods. Also, provide ground cover, may help improve soil structure, OM content, and help reduce erosion (therefore reducing P, sediment, and chemical transport). 

Controlled Drainage

Water management practice that utilizes water control structures such as a flash board riser to adjust (raise or lower) the drainage outlet elevation, thereby adjusting the water level elevation of the area draining to the water control structure and outlet. 

• Flash boards dam the water → forces water levels in the field to the ground surface to get to the ditch and leave

• Changes the hydraulic gradient

• Dissolved oxygen will drop due to organic matter causing anaerobic conditions and then bacteria will break down nitrogen (denitrification) → N2 goes to the atmosphere

• Improves downstream water quality by holding back the water with fertilizers and pesticides

Controlled Drainage Design Specifications

• Used in geographic regions where the land is flat (typical slopes of ~0.5%) Tidewater regions of NC, and lower coastal plain

• Structure size depends on drainage area.

• Pipe diameter is directly related to the watershed size, riser height is

  dependent upon the depth of the ditch/channel.

• Bigger structures will have concrete/cement holding it in place

Outflow Monitoring on Controlled Drainage devices

Notches can be carved into the flashboards to function as weirs. With automated water level loggers, discharge can be calculated over time. Water level is manually checked using the stream stage gage. 

Controlled Drainage Benefits

• Reduces outflow by an average of 20-30%, but is greatly influenced by soil type, rainfall, type of drainage system and management intensity

• Provides a higher water table in the fields, promoting denitrification- NO3-N concentrations 10-20% lower (relative to conventional drainage) have been demonstrated.

• Combined effects of reduced outflow and reduced concentrations equate to an overall 45% N load reduction.

• Phosphorus transport reduced by 35% relative to conventional drainage

• Successful management of controlled drainage focuses on: 1) optimum production efficiency and nutrient utilization by crop and 2) maximum water quality benefits

Summary of Controlled Drainage

•Reduces the amount (volume) of water leaving the farm (N and P)

•Denitrifies the nitrogen at the ditch edge (N).

•Increases crop growth (N and P).

–Greater yields mean that more nitrogen and phosphorus is used by the crop.

Buffers

Vegetated areas adjacent to waterways, drainage canals, lakes, etc., that serve to reduce nutrient, sediment and other pollutant transport from uplands to surface waters → Combination grass, shrub and forested buffers work well

• Forested- woody vegetation, mostly trees adjacent to streams; deep tree roots can take up runoff

• Shrub- wax myrtles, elderberry, small, slow growing trees

• Grass- groundcover to stabilize soil, encourage sheet flow, reduces erosion

Riparian Buffer Zones

Requires 50 feet of riparian area be protected on waterways in the Neuse and Tar-Pamlico Basin.

• Zone 1 = If you have a forest management plan you can legally harvest trees for timber

• Zone 2 = You can thin trees in this zone

Buffer Effectiveness

The potential for buffers to reduce nitrogen loadings to streams is greatly dependent upon the groundwater depth and flow path relative to the riparian vegetation root zones.

• Groundwater well below → not as effective

• Groundwater closer to the root zone → more effective

Phosphorous Removal in Buffers

Phosphorus contributions to stream reduced due to sediment settling out in the buffer.  The vegetation slows the rate of overland flow, and the sediment falls and becomes buried in buffer. Also, some P may be Immobilized by microorganisms or used by plants if they are released from soil.

• As buffer width increases, sediment reduction % increases. However, increasing the buffer widths in coastal plains from 14 to 28’ does not provide as much incremental (% difference) benefits as in the piedmont.

• The piedmont region has sleeper slopes → surface runoff moves at a high velocity and carries a heavier sediment load

For Riparian Vegetation Storage of Nutrients, _______.

tree uptake and storage of nitrogen and phosphorus can be significant. However, nitrogen reduction potential is greatest via the denitrification pathway.

Buffer Width and Phosphorus Removal

• As buffer width increases, phosphorus deliver to waterways decreases.

  After 15 ft, the benefits of additional buffer width declines.

• 1 on y-axis → everything leaves a creek

Nitrogen Reduction Through Riparian Buffers (Subsurface)

After 65 ft, starts to taper off in the increase of %

Stream Restoration

Converting modified streams back to a more natural appearance/characteristics

• more meandering, planting vegetation, root wads for habitat and erosion control

• Natural characteristics to restore: 1) Stream sinuosity (meander) 2) Flood plain connectivity - overbank flow from stream to

  floodplain area adjacent to stream with wetland vegetation

  3) Aquatic habitat - structures in stream channel such as

  uprooted trees that provide shelter for aquatic organisms

  4) Ripple and pool complexes - stream bed features that provide

  areas of relatively deep water (pools) and small water fall like

  features that oxygenate the water

Stream Restoration Construction

• Stabilizing the stream bank with turf mats and root clusters

• Root wads for habitat and erosion control

• Pool - deeper area of water

• Riffle - area where water flow is turbulent and water becomes oxygenated

• Sinuosity- meandering or snaking of stream

• Root wads in the stream provide stream bank stability and aquatic habitat

Wetland Criteria

1. Wetland hydrology - The land must be saturated to the surface or be flooded (moving water) or ponded (stagnant water) during the growing season such that the wetness has an overriding effect on vegetation and soils.

2. Wetland soils - Formed under conditions of saturation, flooding, or ponding that lasted long enough during the growing season to develop anaerobic conditions in the upper part. Ex. Leaf, Rains, Pantego

3. Wetland vegetation - Plants that grow and reproduce in soils that

  are waterlogged and reduced. Ex. Cypress, Rush, Spartina and Water Tupelo

Wetland Restoration

The return of a wetland from a disturbed or altered condition by human activity to a previously existing condition.

• Restoring wetland hydrology through Wetland floodplain excavation → removing soil to get closer to water table and thus restore wetland hydrology

• Wetland planting → hydroseeding (wetland seed is mixed with water, fiber, nutrients and dye and sprayed onto the area on interest) and floodplain planting (people physically plant stuff in the soil)

After a wetland restoration, _______ is performed.

water quality monitoring

• Nitrogen, Phosphorus, and Sediment analysis from automated and manual water samples

• Bacteria analysis on manual water samples

BMP control pollutants when _______.

• You have selected the correct BMPs

• BMPs have been put in the most critical areas of a watershed or river basin

- Critical areas are the watershed areas that generate the greatest proportion of pollution

• Most of the critical areas have been treated with BMPs

• BMPs are managed and maintained

BMP Recommendations - Lower Coastal Plain

• Controlled drainage with 3-6 ft vegetated buffers along field ditches, nutrient management

• Riparian buffers along larger streams (25 ft of woody vegetation)

BMP recommendations - Middle and Upper Coastal Plain

• On average contributes most nitrogen/area

• Deeper ditches that intercept shallow subsurface flows have elevated N concentrations, shallow ditches lower concentrations

• Riparian buffers (25 ft + some grass), controlled drainage (flat fields), nutrient management and in-stream wetlands

BMP Recommendations - Piedmont

• Steeper slopes and more clayey soils increase risk of erosion relative to coastal plain.

• Planting on terraces, contour farming, conservation tillage, grassed waterways and field borders can also reduce erosion but not necessarily N transport. Therefore, riparian buffers (50 ft) recommended with 25 ft of grass and 25 ft of forest.

• May need a level spreader to prevent gullies and provide sheet flow into buffer.

BMP Recommendations - Mountains

Mostly pasture land - buffers (25 – 50 ft) with fencing to prevent cattle from degrading streams