Nulex Liquid Zinc :: Effective Zinc Management

Effective Zinc Management

An infinitesimal amount of this mighty nutrient goes a long way in helping to produce yield gains. Reprinted from Fluid Journal, Volume 2, Number 4

Over the past three issues of the Fluid Journal, we’ve covered effective management of the primary nutrients NPK. In this issue, we will review the principles of effectively managing zinc—an element applied in micro amounts compared to its cousins NPK. How important is zinc? Well, it exists in all living things. It is the 24th most available element in the earth’s crust. Two ounces per ton of feed can prevent parakeratosis in hogs. Two ounces will promote healthy egg and chick development. Without it, no crop would grow. Zinc is involved in the necessary functions of plant growth. It helps produce auxins, a growth-promoting substance that controls growth of shoots. Zinc also forms enzyme systems, which regulate plant life. For a nutrient so vital to plant growth, its deficiency in most soils is one of the true ironies in U.S. agriculture. Surveys of the fifty states report that as high as 92.3 percent of soil samples taken show medium to serious zinc deficiencies! For a very small cost—less than a half bushel of corn per acre—these deficiencies could be corrected and add, as this article will show, substantial bushels per acre. For example, sufficient NPK may be applied to a corn crop to reach 175 bu/A. But, owing to a neglected zinc deficiency, only 150 bu/A are harvested. The penalties for insufficient zinc in this case are 1) wasted NPK that could have produced that other 25 bushels, 2) higher costs per bushel of corn grown and 3) lower net profit. This is what we call the "law of the minimum." Skimping on this micronutrient will cost you dearly in terms of yields lost and what you ultimately deposit in the bank. Just one quart/A of liquid zinc in a fluid starter applied on corn can avert this "law of the minimum."

Crop sensitivity

All plants require zinc, but their ability to use available zinc and extract zinc differs (Table 1). It should be noted however that variability is likely to exist within a given species. For example, the Sanilac variety of pea bean is highly susceptible to Zn deficiency whereas the Great Northern variety is quite tolerant. Similarly, Russet Burbank potatoes develop zinc deficiency under certain field conditions where White Rose show no symptoms. Researchers have demonstrated differential zinc uptake of inbred corn lines grown in nutrient solution, indicating genetic control of translocation, use, and requirements of zinc. Thus, the sensitivity of crops to zinc deficiency in the table should be taken as generally representative.

TABLE 1. Sensitivity of selected crops to zinc deficiency.
Very Sensitive	Mildly Sensitive	Insensitive
Beans–lima and peas	Alfalfa	Asparagus
Castor beans	Clovers	Carrots
Citrus	Cotton	Forage grasses
Corn	Potatoes	Mustard
Flax	Sorghum	Peas
Fruit trees	Sudangrass	Peppermint
Grapes	Sugar beets	Safflower
Hops		Small grains
Onions
Pecans
Pine
Soybeans

Soil testing

Soil tests for zinc are most often performed using an acid extract such as 0.1 N CHI or a chelating agent such as a DTPA extract. The DTPA with ammonium bicarbonate test is preferred for soils containing free CaCO3 and can be requested. Advantages of the DTPA extraction are that several micronutrients can be analyzed simultaneously and greater control can be exerted on sample longevity. Studies have shown that soils that may be high in total zinc may not be necessarily high in plant-available zinc, as indicated by the extract. Comparisons of five different extracts on Ontario soils, using corn as an indicator crop, showed that no single extract adequately represents all field conditions. This suggests that growers should use tests indigenous to their areas.

Deficiency symptoms

There are a number of visual symptoms in crops that will alert you to zinc deficiencies:

Corn–Yellow streaks between veins. Dead areas in older leaves. Shortening of the internodes. Stunting of the plant. Silking and tasseling delayed. Chalky kernels. Reddish-brown coloration on portions of plant.
Sorghum–Deficiency symptoms in grain sorghum are similar to corn, but less pronounced. Zinc deficiency appears to retard development and maturation of the heads.
Cotton–Delay in flowering. Reduction in boll size. Plant produces only a few squares and sheds them around time of anthesis.
Soybeans–Interveinal chlorosis. Necrosis of lower leaves. Poor pod initiation and development.
Wheat–Chlorotic and necrotic stripes along each side of midrib. Shortened leaves. Oil-soaked appearance in leaves, followed by collapse of leaves across middle.

Behavior in soil

One of the natural causes of zinc deficiency is tie-up in high alkaline soils—that is, calcareous or high-pH soils. Zinc deficiency is also found in soils high in organic matter. Sandy soils, soils high in clay content, and soils naturally high in phosphates (which tend to tie up zinc) are also causes of deficiencies. Surface soils contain a greater proportion of available zinc than subsoils. It is a general belief that surface accumulation of Zn is caused by subsurface mining by plant roots, decay of organic matter, and subsequent deposition at the surface. Cool, wet soils can cause zinc deficiency by reducing root growth Zinc is very sensitive to cold temperatures. The movement of zinc is slower in acidic soils, which may reduce crop absorption from spatial unavailability. Liming of soils raises the pH and may help eliminate some movement problems, but these gains are usually offset because the higher pH increases soil zinc-fixing capacity, especially in soils high in phosphate. Because of its high insolubility and immobility in the soil, zinc should be applied under the subsoil with a starter fertilizer or by root zone handing.

Man-made deficiencies

Cultural practices can also cause zinc deficiencies in soils.

Fertilization. Heavy applications of phosphate fertilizer several years running can induce a zinc deficiency. Crop uptake is reduced. This may be due to competitive ion effects, fixation of zinc in unavailable forms, or physiological imbalances. Growers should also be aware that N fertilizers can increase crop growth to a point where zinc requirement of plants exceeds availability in soil.
Land renovation. Field areas where top soil is removed can cause zinc deficiency because zinc is always concentrated near the surface.
Soil compaction. Compacted areas will cause zinc deficiencies because of zinc’s immobility—it doesn’t move with the soil water.
Depletion. High yields and heavy cropping can deplete soils of zinc.

Making it pay

As stated earlier, proper use of zinc in a fertility program can add substantial bushels per acre. We’ll look at several examples: Kansas–In this study, the land was low in P and Zn. Adding 80 lbs/A of a liquid phosphate without zinc actually depressed corn yields when compared to the cheek, as shown in Figure 1. But correcting the P/Zn imbalance by adding 80 Ibs/A of P with 10 lbs/A of Zn boosted yields over cheek by 62.2 bu/A! A good rule of thumb is: if you’re low in phosphorus and low in zinc, apply troth in your fertilizer program.

TABLE 2. Effect of zinc application in eliminating zinc/phosphorus imbalance and improving corn yield. Kansas Stae University.
	Yield–Bushels per Acre
Check	100.9
80 lbs/acre P2O5, no zinc	73.4
08 lbs/acre P2O5 + 10 lbs/acre zinc	162.6

Nebraska–The effect of different rates of zinc applied with a fluid starter on corn was shown in this study. Note how one pound of zinc increased corn yields by 29 bu/A over cheek in 1975 and 77 bu/A over check in 1976 (Table 3). The crop was grown in an irrigated field on a sandy soil having a pH greater than 7.

TABLE 3. Effect of rate of applied zinc on yield of corn on irrigated sandy soils having pH greater than 7.0.
	Yield–Bushels #2 Corn per Acre
Zinc Applied Pounds per Acre	1975	1976	Average
0	101	62	82
0.1	107	130	119
0.3	119	135	127
1.0	130	139	135
3.0	122	142	132

In another Nebraska study, it has been shown how even an infinitesimal amount of Zn banded near the seed in a fluid starter program can give spectacular responses. Note how only one-tenth of a pound of zinc applied per acre increased corn yield 57 bu/A when compared with cheek (Figure 3)! A mere dollars worth of zinc placed below and to the side of the seed nearly doubled the yield.

TABLE 4. Effect on corn yield when banding zinc near seed. University of Nebraska.
Zinc Applied–pounds/acre	Yield–bushels/acre
0	62
0.1	120
0.3	127
1.0	133

Zinc in fluids During the early period when fluid and suspension fertilizers began to gain in popularity, researchers Mortvedt and Giordano reported that ZnO in fluid fertilizers was more effective than ZnO incorporated with granular fertilizer. Distribution was markedly superior in fluids. Other studies in Kansas have shown 12 to 20 bu/A increases in corn yield where zinc was banded with polyphosphates at planting time, versus yield losses when zinc was added to dry fertilizers and broadcast. Superior distribution, placement, and incorporation paid off with an element whose nasty property is high insolubility.

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