Nutrient Placement and Movement Under Zero-till Conditions

Illinois Fertilizer Conference Proceedings
January 25-27, 1993

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Nutrient Placement and Movement Under Zero-till Conditions

Lyle Paul¹

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Introduction

As more grain producers change their operations to include reduced or no tillage, there is less opportunity for mixing nutrients into the soil. Some advocates of zero-till have said that the benefits of zero-till are increased if the soil is left undisturbed for a period of time (several years). They feel that this benefit is greater than any negative effect from the lack of mixing the fertilizer into the soil. There has been a concern by others that occasionally, fertilizer and especially lime need to be mixed into the soil to get maximum yields. This study attempts to answer the question of whether mixing of fertilizer and lime into the soil will benefit corn and soybean yields.

Materials and Methods

This study is a randomized complete block design with four replications with corn and soybeans being planted each year in a corn-soybean rotation. The initial treatments were to raise the pH to 6.5, P₁ to 50, K to 300, leave them untreated, use maintenance applications of fertilizer or 1/3 of the needed lime. One-half of the plots were plowed after liming and fertilization and one-half were untilled. In succeeding years all plots will be no-tilled.

These plots were established on Flanagan silt loam and Drummer silty clay loam. The average initial soil test levels were pH-5.6, P₁-39, and K-225. This field has been in a corn and soybean rotation with minimal fertilizer added over a number of years.

Powdered limestone that would pass a 200 mesh screen was applied to the individual plots according to the experimental plan and to the average of the four incremental soil tests of the individual plots. Fertilizers in the forms of 0-46-0 and 0-0-60 were also applied to the individual plots according to the plan and design. After fertilizer application in the spring of 1991 the plots selected for incorporated fertilizer were disked once and moldboard plowed. After plowing, the incorporated plots were disked twice and field cultivated once before planting. After planting the only additional disturbance to any plots was a row cultivation. The entire plot area was row cultivated using a zero-till cultivator. Plant samples during the summer and grain samples at harvest were collected from all of the plots. All plots were machine harvested and yield measurements were taken.

In 1992, corn (Pioneer Hybrid 3417) was planted on May 4 at 29,100 seeds per acre in 30 inch rows. Nitrogen was applied on June 10 at 180 lb N/acre as UAN. The UAN was injected at a depth of 3" inches using a knife applicator with knives on thirty inch centers.

The soybean crop was planted on May 13th. The variety was DeKalb Plant Genetics variety CX259. The beans were planted with a Tye No-till drill in eight inch rows at a seeding rate of 90 pounds per acre. Herbicides were used in both crops and adequate weed control was achieved.

Results and Discussion

The yield differences in 1991 were due more to tillage operations and their effects than to rate or placement of fertilizer. A confounding factor was the difference in weed control under the different systems. All plots were treated with herbicides, but the efficacy of weed control was not the same for all plots.

The analysis from the plant and grain samples taken during the 1991 growing season (Tables 3, 4, 5, 6, 7, and 8) show that some of the nutrients were below the critical levels suggested in the Agronomy Handbook. The levels of liming and fertilization and incorporation affected the relative percentages of some nutrients more than others.

Corn plants had lower than critical levels of nitrogen, phosphorus, potassium and boron. Soybean plants had lower than the critical level of potassium. In both crops tillage made more of a difference in nutrient levels than did fertilizer or liming treatment. This difference may have been due to positional availability of the nutrients or the ability of the root to more easily grow through the tilled soil profile.

Nutrient removal in the grain from the study areas was lower than the amount that should have occurred according to nutrient removal tables. This may have been a reflection of the plant samples being below the critical levels or have been a reflection of the low yields.

Yields in 1992 (Tables 1 and 2) responded to fertilizer and lime applications, and continued to show some of the effects of the tillage operation that incorporate the fertilizer and lime in 1991. This occurred in both the corn and soybean crops, but to a greater degree in the corn crop. The plots that received no lime and fertilizer should have had the same yields, but there were differences in these yields and that would be the result of the tillage operation in the spring of 1991.

Given the low pH and fertility levels at the start of the study there was a benefit to the application of lime in the soybean crop and to the application of fertilizer in both crops. In corn with surface application of lime and fertilizer, increasing levels of fertilizer will show stronger results immediately.

Additional study will be necessary to determine if the original placement and amounts of fertilizer and lime will make greater differences in the results over time.