environmental effects of agriculture (non-point source pollution)

Environmental Effects Environmental Effects of Agricultureof Agriculture

(Non-point Source (Non-point Source Pollution)Pollution)

Introduction

• Agriculture generally behind the times (1990 –> USDA decided that water quality is a problem in the US - doh!)

• Can cause severe environmental impacts

• Agro-pollution hard to address – farming historically seen as stewardship of the land (actually stewardship of farmland)

Why agriculture?

• The Need to Feed

• Unpredictable services offered by unmanaged system (natural environment)

• Agriculture = managing environment

Pollution from Agriculture

• Agriculture often considered a life-style

AR is a large exporter of pollution – Gulf of Mexico

• Agriculture is hardest non-point source problem to solve

• Only significant progress pesticides (but not a big problem anyway)

The Process of Agriculture

A. Crop selection 1. based on high yield and market need (exception –

dairy farmer growing corn for cattle)

2. 350,000 spp. of terrestrial plants , < 2,000 ever cultivated or used for food

3. Wheat, corn, rice meets most of worlds caloric needs

4. US uses only about 25 crops -> low exploitation of plant resources

The Process of Agriculture (con’t)

B. Propagation1. Tillage – prepare soil

to receive crop

2. Nutrient management

The Process of Agriculture (Con’t)

C. Protection

Pest management

Note: pesticides

synthesized to kill, then

quickly breakdown into

“harmless” residues

III. Modern Production Agriculture

A. Use of energy in agriculture to increase yield

1. Agriculture is an extremely E. intensive (HO Table 18.2)

2. Ways to save E. in agriculture

a. Better herbicides (more specific)

b. Better irrigation (polypipe)

c. Alternative N2 inputs

d. Fuel (avg fruit travels 1,300 miles to market increase regional markets

Modern Production Agriculture (con’t)

B. Other factors affecting yield

1. Environmental conditions (HO) a. Spring - increasing temp, water needs

b. Summer – need 25% light for max. Ps

Note: often water stressed get decr. in mass because using stored E. to survive

c. Fall – plants start to die harvest just before

Modern Production Agriculture (con’t)

B. Other factors affecting yield (con’t)

2. Manipulation by farmer

a. tillage (plowing) manipulates soil, air, water

b. altered nutrient cycles

- bury dead organic matter

- “ weed seed bank deep so no germinate

- fertilization N, P, K

Modern Production Agriculture (con’t)

C. Chemical fertilization

1. Forms of chemical fertilizers

a. Nitrogen (N)NH4NO3 (ammonium nitrate) – cheap but explosive

NaNO3 (sodium nitrate) good but expensive

CO(NH2)2 (urea) expensive, effective but may scorch

NH3.H2O (anhydrous ammonia) cheaper, high loss by leaching

NH4.OH (aqueous ammonia) less cheap, less “ “ “

Modern Production Agriculture (con’t)

2. Phosphorous (P)

Phosphate rock – grind into powder, cheap but very water insoluble

CaH2PO4 (superphosphate) together make up

Ca(H2PO4 )2 ( “ ) 50% of all P used

H2P2O4 (phosphoric Usually extract from rock,

H3PO4 acid) treat with H2SO4 use

Modern Production Agriculture (con’t)

3. Potassium (K)KCl (potassium chloride) – most widely

used K fertilizerK2SO4 (pot. sulfate) – expensive, but S has

some fertilizer valueK2NO3 (pot. nitrate) – expen, mainly used

for vegetablesPotash (K-oxide) – v. good for certain crops

(potatoes)

Modern Production Agriculture (con’t)

2. Ratio and Use of Fertilizers

N : P : K

10 : 10 : 10 <-- % by weight

Above is very soluble to increase movement into plants but also increases runoff OH