A Field and forage crops

Manure and sewage have been used for centuries as fertilizers and soil amendments to produce food for human and animal consumption. Generally, manure and sludges are applied to crops that are most responsive to nitrogen inputs. Field crops that are responsive include corn, sorghum, cotton, tobacco, sugar beets, and cane.

Sewage sludge should not be used on tobacco. The liming effect of the sludge can enhance the incidence of root diseases of tobacco. It can also elevate cadmium levels in tobacco leaves, rendering it unfit for marketing (USDA 1986).

Cereal grains generally do not receive fertilizer application through manure because spreading to deliver low rates of nitrogen is difficult. Small grains are prone to lodging (tipping over en masse under wet, windy conditions) because of the soft, weak cell walls derived from rapid tissue growth.

Legumes, such as alfalfa, peanuts, soybeans, and clover, benefit less by manure and sludge additions because they fix their own nitrogen. The legumes, however, use the nitrogen in waste products and produce less symbiotically fixed nitrogen. Alfalfa, a heavy user of nitrogen, can cycle large amounts of soil nitrogen from a depth of up to 6 feet. Over 500 pounds per acre of nitrogen uptake by alfalfa has been reported (Schuman & Elliott 1978; Schertz & Miller 1972).

The great danger of using manure and sludges on legume forages is that the added nitrogen may promote the growth of the less desirable grasses that are in the stand. This is caused primarily by introducing another source of nitrogen, but it can also be a result of the physical smothering of legume plants by heavy application cover of manure.

Grass tetany, a serious and often fatal disorder in lactating ruminants, is caused by a low magnesium content in rapidly growing cool season grasses. Cattle grazing on magnesium deficient forage develop health problems. High concentrations of nitrogen and potassium in manure applications to the forages aggravate the situation. Because of the high levels of available nitrogen and potassium in manure, early season appli cations on mixed grass-legume forages should be avoided until the later-growing legume is flourishing because legumes contain higher concentrations of magnesium than grasses.

Table 6-3

General effects of trace element toxicity on common crops (Kabata & Pendias 1984)

Table 6-3

General effects of trace element toxicity on common crops (Kabata & Pendias 1984)

Element

Symptoms

Sensitive crop

Al

Overall stunting, dark green leaves, purpling of stems,

Cereals.

death of leaf tips, and coralloid and damaged root system.

As

Red-brown necrotic spots on old leaves, yellowing and

(No information.)

browning of roots, depressed tillering.

B

Margin or leaf tip chlorosis, browning of leaf points, decaying

Cereals, potatoes, tomatoes,

growing points, and wilting and dying-off of older leaves.

cucumbers, sunflowers, mustard.

Cd

Brown margin of leaves, chlorosis, reddish veins and petioles,

Legumes (bean, soybean), spinach

curled leaves, and brown stunted roots.

radish, carrots, and oats.

Co

Interveinal chlorosis in new leaves followed by induced Fe chlorosis

(No information.)

and white leaf margins and tips, and damaged root tips.

Cr

Chlorosis of new leaves, injured root growth.

(No information.)

Cu

Dark green leaves followed by induced Fe chlorosis, thick,

Cereals and legumes, spinach,

short, or barbed-wire roots, depressed tillering.

citrus, seedlings, and gladiolus.

F

Margin and leaf tip necrosis; chlorotic and red-brown

Gladiolus, grapes, fruit trees, and

points of leaves.

pine trees.

Fe

Dark green foliage, stunted growth of tops and roots, dark brown

Rice and tobacco.

to purple leaves of some plants ("bronzing" disease of rice).

Hg

Severe stunting of seedlings and roots, leaf chlorosis and

Sugarbeets, corn, and roses.

browning of leaf points.

Mn

Chlorosis and necrotic lesions on old leaves, blackish-brown

Cereals, legumes, potatoes, and

or red necrotic spots, accumulation of MnO2 particles

cabbage.

in epidermal cells, drying tips of leaves, and stunted roots.

Mo

Yellowing or browning of leaves, depressed root growth,

Cereals.

depressed tillering.

Ni

Interveinal chlorosis in new leaves, gray-green leaves, and

Cereals.

brown and stunted roots.

Pb

Dark green leaves, wilting of older leaves, stunted foliage,

(No information.)

and brown short roots.

Rb

Dark green leaves, stunted foliage, and increasing amount of shoots.

(No information.)

Se

Interveinal chlorosis or black spots at Se content at about

(No information.)

4 mg/L and complete bleaching or yellowing of younger leaves

at higher Se content; pinkish spots on roots.

Zn

Chlorotic and necrotic leaf tips, interveinal chlorosis in new leaves,

Cereals and spinach.

retarded growth of entire plant, injured roots resemble barbed wire.

Perennial grasses benefit greatly by the addition of manure and sludges. Many are selected as vegetative filters because of their efficient interception and uptake of nutrients and generally longer active growing season. Others produce large quantities of biomass and thus can remove large amounts of nutrients, especially nitrogen, from the soil-plant system.

Bermudagrass pastures in the South have received annual rates of manure that supply over 400 pounds of nitrogen per acre without experiencing excessive nitrate levels in the forage. However, runoff and leaching potentials are high with these application rates, and they must be considered in the utilization plan.

Grass sods also accumulate nitrogen. An experiment in England carried out for 300 years at Rothamsted showed a steady increase in soil nitrogen for about 125 years before leveling off when an old plowed field was retired to grass (Wild 1988). However, where waste is spread on the soil surface, any ammonia nitrogen in the waste generally is lost to the air as a gas unless immediately incorporated.

Grass fields used for pasture or hay must have waste spread when the leaves of the plants are least likely to be contaminated with manure. If this is done, the grass quality is not lessened when harvested mechanically or grazed by animals (Simpson 1986).

Spreading wastes immediately after harvest and before regrowth is generally the best time for hay fields and pastures in a rotation system. This is especially important where composted sludge is applied on pasture at rates of more than 30 tons per acre. Cattle and sheep ingesting the compost inadvertently can undergo copper deficiency symptoms (USDA 1986).

Some reports show that manure applied to the soil surface has caused ammonium toxicity to growing crops (Klausner and Guest 1981). Young corn plants 8 inches high showed ammonia burn after topdressing with dairy manure during a period of warm, dry weather. The symptom disappeared after a few days with no apparent damage to the crop. This is very similar to corn burn affected during sidedressing by anhydrous ammonia. Liquid manure injected between corn rows is toxic to plant roots and causes temporary reduction in crop growth. Warming soil conditions dissipate the high ammonium levels, converting the ammonium to nitrates, and alleviate the temporary toxic conditions (Sawyer and Hoeft 1990).

Table 6-4 Interaction among elements within plants and adjacent to plant roots

Major

Antagonistic

Synergistic

Trace

Antagonistic

Synergistic

elements

elements

elements

elements

elements

elements

Ca

Al, B, Ba, Be, Cd, Co, Cr,

Cu, Mn, Zn

Cu

Cd, Al, Zn, Se, Mo, Fe,

Ni, Mn, Cd

Cs, Cu, F, Fe, Li, Mn, Ni,

Ni, Mn

Pb, Sr, Zn

Zn

Cd, Se, Mn, Fe, Ni, Cu

Ni, Cd

Mg

Al, Be, Ba, Cr, Mn, F,

Al, Zn

Cd

Zn, Cu, Al, Se, Mn, Fe,

Cu, Zn, Pb,

Zn, Ni, Co, Cu, Fe

Ni

Mn, Fe, N

P

Al, As, B, Be, Cd, Cr,

Al, B, Cu, F,

B

Si, Mo, Fe

Mo, Fe

Cu, F, Fe, Hg, Mo, Mn,

Fe, Mn, Mo,

Al

Cu, Cd

(No evidence.)

Ni, Pb, Rb, Se, Si,

Zn

Pb

---

Cd

Sr, Zn

Mn

Cu, Zn, Mo, Fe, Ar, Cr,

Cu, Cd, Al,

K

Al, B, Hg, Cd, Cr, F,

(No evidence.)

Fe, Co, Cd, Al, Ni, Ar, Se

Mo

Mo, Mn, Rb

Fe

Zn, Cr, Mo, Mn, Co, Cu,

Cd, B

S

As, Ba, Fe, Mo, Pb, Se

F, Fe

Cd, B, Si

N

B, F, Cu

B, Cu, Fe, Mo

Mo

Cu, Mn, Fe, B

Mn, B. Si

Cl

Cr, I

(No evidence.)

Co

Mn, Fe

(No evidence.)

Ni

Mn, Zn, Cu, Cd

Cu, Zn, Cd

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