WW-06702-GO     July 2009  

For Ridge-Till and No-Till Corn Production

Postharvest to Postemergence
Fertilizer Management

Copyright ©  2002  Regents of the University of Minnesota. All rights reserved.

Efficient and effective fertilizer use is one management practice that is essential for profitable corn and soybean production in ridge-till and no-till planting systems. With the popular corn/soybean rotation, planning for fertilizer use with either of these tillage systems should start prior to soybean harvest. Application of phosphate and/or potash fertilizers should be completed in the fall of the soybean year, and application of nitrogen fertilizers should be completed in the early part of the growing season during the following year. This publication describes fertilizer management practices that should be used for profitable corn and soybean production in these two tillage systems.

Begin with a Soil Test

As with all other crop production systems, soil testing is the important "first step" for economic fertilizer management in both no-till and ridge-till planting systems. Current University of Minnesota fertilizer recommendations are based on the combination of an individual producer's yield goal and the results of the analysis of a representative soil sample. Yield goals vary with individual producers and are affected by personal knowledge of the production potential of soils, individual management skills, and optimism. Therefore, yield goal should vary with each producer as well as among individual fields farmed by each producer.

Analytical procedures used in the various soil testing laboratories are standardized. Procedures used for collecting soil samples can also be standardized. This standardization in sampling and analysis should provide the grower with reasonably accurate information about the soil fertility status of the production fields. Sampling procedures, however, differ for the various nutrients. Recommended soil sampling procedures are described in the sections that follow.

Sampling for Immobile Nutrients:

Phosphorus, potassium, and zinc are relatively immobile in soils and move very little from the point of application. Relative levels of these nutrients are determined by analyzing soil collected from a depth of 0 to 6 inches. For the ridge-till system, the sample should be taken from the shoulder of the ridge (see Figure 1 ). For no-till planting systems, the sample should be taken at a distance of 6 inches from the row if row spacing is 30 inches. When soybeans are planted without tillage in narrow rows, a random collection of samples would be appropriate.

If potash and/or phosphate fertilizer is applied in a band and the location of the band is known, the collection of samples from the zone where the band is applied should be avoided. Soil test values for potassium as affected by three repeated annual applications of relatively high rates of potash fertilizer are shown in Figure 2 . The highest soil test values for potassium extend to approximately 6 inches from the row and to a depth of 3 to 6 inches. Research has also shown that a substantial portion of the corn root system develops in the ridge when the ridge-till planting system is used. Based on the information available at this time, the collection of the soil sample from the shoulder of the ridge (6 to 9 inches from the row) to a depth of 6 to 8 inches should be satisfactory for an accurate evaluation of the relative level of phosphorus, potassium, and zinc.

Sampling for Nitrogen:

Except for the sandy soils (sandy loams, sands, loamy sands), a soil test for nitrogen is available to help with fine-tuning nitrogen recommendations for corn in most of Minnesota. Collection of soil samples to a depth of 24 inches is necessary for an accurate measure of residual or carryover nitrate-nitrogen (NO ₃ -N).

This fall nitrate test is appropriate for western Minnesota. Collection of the sample at or near planting is suggested for southern and southeastern Minnesota.

Soil samples collected following soybean harvest in three ridge-till fields in central Minnesota showed that measured nitrate-nitrogen (NO ₃ -N) can vary ( Table 1 ). In each field, the amount of NO ₃ -N found below the row was less than the amount measured in the middle of two rows where the row spacing was 30 inches. In both cases, soil was collected to a depth of two feet. The lower values between the rows are probably a consequence of greater soybean root activity directly below the row.

Table 1. Concentration of nitrate-nitrogen in the fall for three ridge-till fields that had been planted to soybeans. Samples were collected to two feet.

		Location of Sample
County		Row	Middle of 2 Rows
	lb. NO 3 -N/acre
Renville - A		48	110
Renville - B		68	75
Kandiyohi		48	67

The optimum rate of nitrogen fertilizer at each site was predicted by averaging the NO ₃ -N concentrations found below the row and in the middle of two rows. Therefore, when sampling for nitrogen, collect ½1/2 of the soil cores from under the row of the previous crop and ½ of the cores from the middle of two rows. Mix all cores together before submitting the sample for analysis.

This same procedure can be followed if no-till corn follows soybeans planted in 30-inch rows. When no-till corn follows soybeans planted in narrow rows, a random sampling pattern collecting soil to a depth of two feet would be suggested.

Fall Banding

Results of several research projects have shown that the banded placement of both phosphate and potash is superior to broadcast applications for both ridge-till and no-till planting systems. These nutrients are not mobile in soil. If broadcast, there is very little, if any, opportunity for incorporation into the root zone. If placed in a band below the seed, these nutrients are in a position when they can be used effectively by the growing crops.

In Minnesota, the ideal time for band application of phosphate and potash is in the fall following soybean harvest. This band can be applied under the row of the previous crop or on the shoulder of the ridge. Placement below the row disturbs a smaller portion of the ridges and will not cause problems with planting in the following spring. There are various coulter and knife assembles on the market that can be used to band the fertilizer.

The banded application of phosphate and potash in the fall will substitute for the use of starter fertilizer at planting. There is no benefit from using a combination of a fall band and starter fertilizer at planting. There is also no need to combine the use of a fall band with "pop-up" (seed-placed) fertilizer in the spring. If the fall band is placed 3-½ to 4 inches below the soil surface, the fertilizer should be below the seed at planting unless a large portion of the ridge is removed in the planting operation. The general location of the banded fertilizer before and after planting is shown in Figure 3.This band below the seed is an ideal location for phosphate and potash to stimulate the early growth and development of the corn crop.

The banded application of phosphate and potash in the fall is also appropriate for no-till planting systems. If possible, the band should be placed 3-½ to 4 inches below the soil surface. The corn can be planted on top of this band.

Research projects conducted in the fields of several ridge-till farmers have shown that the banded application of potash has a positive economic effect on corn yield. Research at the West-Central Experiment Station at Morris has shown that rates of potash used in a band for ridge-till production are also appropriate for no-till production systems.

A rate of 40 to 50 lbs. K ₂ O per acre is suggested for corn production when corn follows soybeans even though soil test values for potassium are in the medium or high categories. This rate should be increased to 60 to 80 lbs. K ₂ O per acre when the soil test for potassium is in the low category and is adequate for corn following soybeans. These rates should be doubled if the banded fertilizer is to be applied once in two years for a corn-soybean rotation.

The rates of potash, suggested above, are the results of several research trials conducted in ridge-tilled fields. It's important to emphasize that small rates of K ₂ O (10-20 lbs. K ₂ O per acre) applied in a starter at planting are not adequate for optimum yield in these planting systems.

Suggested rates of phosphate for band application vary with yield goal and the soil test value for phosphorus. These suggested rates are summarized in Table 2. These rates are also appropriate for no-till production systems.

Phosphate fertilization for soybean production is different from phosphate use for corn. Phosphate fertilizers will not be needed for soybeans if the soil test value for phosphorus is higher than 10 ppm (Bray procedure) or 8 ppm (Olsen procedure). Therefore, it's important to use a regular soil testing program to measure the relative level of phosphorus before fertilizer is applied in a band in the fall of the soybean year.

Table 2. Phosphate recommendations for banded application in ridge-till and no-till planting systems.

		Phosphorus (P) Soil Test (ppm)*
Yield	Bray:	0-5	6-10	11-15	16-20	21-25	26+
Goal	Olsen:	0-3	4-7	8-11	12-15	16-19	20+
bu./acre	P2O5 to apply (lb./acre)
70-90		25	20	15	10-15	10-15	0
91-110		30	20	20	10-15	10-15	0
111-130		40	25	20	10-15	10-15	0
131-150		45	30	25	10-15	10-15	0
151-170		50	35	30	10-15	10-15	0
171-190		55	40	30	10-15	10-15	0
191+		60	45	35	10-15	10-15	0

Fertilizer Applied At Planting

The application of phosphate and potash as a starter at planting is a good alternative for growers who do not apply these nutrients in a band in the fall. The traditional placement at 2 inches to the side of, and 2 inches below the seed is not a requirement. It is important that the starter fertilizer be placed at or below seed level. To be most effective, however, the starter fertilizer band should be no further than 3 inches from the seed. These placement suggestions are appropriate for both ridge-till and no-till planting systems. The rates of phosphate and potash suggested for use in a starter fertilizer are the same as those suggested for the fall banded application.

It is possible to apply some fertilizer in contact with the seed at planting. This placement is frequently referred to as a "pop-up." However, rates are limited with this placement option. High rates of nitrogen, potash, or nitrogen-potash combinations could reduce germination if this placement option is used. This method of fertilizer application is not satisfactory for the rates of potash required in ridge-till and no-till planting systems.

Nitrogen Application After Planting

Options for fertilizer use after planting in these tillage systems are restricted to the use of nitrogen. Nitrogen is mobile in soils. Therefore, any source can be managed in a variety of ways to have an equal effect on yield.

Broadcast application of urea (46-0-0) or liquid nitrogen (28-0-0) without incorporation is not recommended either before or after planting. When broadcast in these tillage systems, these sources are placed in contact with crop residue. The nitrogen can be lost by either volatilization or immobilization in the crop residue. If nitrogen is lost, there can be a substantial reduction in yield.

The application of a preemergence herbicide with 28-0-0 in a band over the row at planting is a popular option for many who use the conservation tillage planting systems. This weed and feed option can supply some of the nitrogen needed by the actively growing corn crop early in the growing season. If used with a herbicide in a band, the band width should be adjusted so that contact of crop residue with liquid nitrogen is kept at a minimum.

Application of nitrogen fertilizer in combination with cultivation for weed control is a good option for the ridge-till planting system. It is possible to adapt cultivators so that any nitrogen source can be applied in this way. Split applications of nitrogen fertilizers are suggested for corn production on sandy soils (sandy loams, loamy sands, sands).There are a number of choices to use for a split application. All have advantages and disadvantages. Therefore, the management of split applications of nitrogen on sandy soils varies with the individual grower.

Split applications of nitrogen are not necessary for ridge-till corn grown on soils that are not sandy. Research conducted in Kandiyohi County showed some advantage for split applications when the rates of applied nitrogen were low (60 lb. nitrogen per acre, see Table 3 ). This advantage, however, disappeared when more common economical rates were used.

Table 3. The effect of rate and frequency of nitrogen fertilizer application on corn yield in a ridge-till planting system.

N Applied
Preemergence	1st Cultivation	Yield
- - - - - - - - - - - - - - - - lb./acre - - - - - - - - - - - - - - -		bu./acre
0	60	139
30	30	154
0	120	158
30	90	160
0	150	164
30	120	163

Application of nitrogen fertilizer with a cultivator is not an option for no-till planting systems. For these systems, the nitrogen fertilizer should be knifed below the residue remaining from the previous crop. Using this equipment, nitrogen can be applied in this planting system in the fall, in the spring before planting, or as a sidedress treatment.

George Rehm is professor and extension soil scientist, soil fertility, for the College of Agriculture, Food, and Environmental Sciences.

Produced by the Educational Development System, Minnesota Extension.

Produced by Communication and Educational Technology Services, University of Minnesota Extension.

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