Jay W. Johnson
1. Can no-till work in all types of soils?
While it is generally possible to produce a crop by using no-tillage on any field, maximum returns will normally be achieved by matching the proper tillage system to the soil type.
Our experience with no-till agriculture has shown that no-till works best on soils that have relatively good drainage. On soils with relatively poor drainage, corn has been successfully grown without tillage if the corn follows soybeans in a crop rotation. Corn following corn has proven to be unsatisfactory on untitled, wet soils.
2. Should P and K be incorporated in some way with no-till?
Immobile nutrients like P and K are most efficiently taken up if they are placed in moist soils where roots are actively feeding. Under high residue conditions, it is difficult to measure a yield advantage from incorporation of nutrients. Under low residue situations, however, research has shown that it is important to place immobile nutrients into the soil to insure uptake. We have found that a band placement, below and to the side of the seed, is the most efficient method of P and K application in no-till corn production.
Reference: 'Response of No-till Corn to N, P, or K," 1982 Soil Fertility Research
3. How much and when should P & K be applied to no-till corn? Ridge till corn?
The rate of P and K to apply to corn is dependent on the soil test levels of these nutrients, yield goals, and to some extent the method of application.
As mentioned above, a planter banded placement of P and K is recommended in no-till corn. If these two nutrients must be surface applied, it is best to apply them in the fall so that you can maximize their movement into the soil by extending the time for leaching. This is especially important when residue levels are low since under such conditions root proliferation near the soil surface would be minimal.
When a ridge till system is used for corn, P and K are also best applied through the row. The nutrients from a broadcast application will move into the row zone when the ridges are formed. Traditionally, the ridges are made in June. As a result, fertilizer that was added in the spring will not be incorporated into the ridge until it is too late to benefit the current crop; therefore, when surface application is used in ridge till systems, the native fertility levels must be high for a broadcast program to give optimum yields.
4. How can we build up soil levels of P and K in a no-till system?
If the main objective of the fertilizer program is to build soil levels of P and K under a no-till system and if large quantities of fertilizer will be needed to do this, most of the fertilizer must be broadcast so that salt problems will be minimized.
It normally takes 10 lbs. of P2O5 and 2-10 lbs of K2O per acre to increase soil test values 1 lb./A for a 6 2/3 inch acre slice? Without mixing, P and K will move very slowly into the soil profile (about 1/2-1 inch per year). Therefore, a buildup program is very slow for the 4-8 inch soil depth.
We recommend that only 20-100 units of fertilizer be applied annually through the planter.
For information on the use of N fertilizer under no-till conditions, refer to the section entitled "Nitrogen".
5. What is going to be the result of long term use of anhydrous and lime applied only to soil surface?
In a continuous no-till program, injection of anhydrous ammonia at a depth of 6-8 inches will cause the formation of an acid zone below the surface applied lime. Nevertheless, research conducted at Iowa State has found that this acid zone will tend to disperse through the top 6-8 inches of soil. In addition, some of the surface applied lime should leach down and help neutralize the acid. To date, no negative, long term effects of using anhydrous ammonia in conjunction with surface applied lime have been observed.
6. Can we expect to achieve high yields continuously using no-till technology or do we need to plan periodically to plow a field to get mixing and distribution of nutrients? If mixing is suggested, what time frame should be considered and what technology is most likely to give the desired result?
After approximately 25 years of experience with no-till systems on fertile soils, we have not been able to demonstrate the need for plowing to improve the distribution of nutrients within the top 6 inches of soil. Nevertheless, on soils that have a relatively low fertility level, some mixing and redistribution of nutrients may be desirable. This remixing could enhance root proliferation, which could in turn improve water and nutrient uptake. A good, practical rotation would be to have corn/soybeans for 2-3 years, followed by a small grain or forage crop seeded in summer or fall. Prior to the seeding of the small grain or forage, you could add any needed lime and perform deep tillage. Tillage done during summer or early fall usually causes minimal erosion. Also, the small grain or forage would provide vegetative cover during the fall and winter; this cover would help to protect the soil from erosion. In general, a tillage operation would only need to occur once every 3-5 years on most Ohio soils.
7. Discuss no-till corn use of surface applied N-P-K, especially in long-lay meadows with low P & K soil test levels.
In no-till fields that follow a long term meadow, surface applied fertilizers have been adequate in most of Ohio. The meadow crop normally produces high residue conditions at the soil surface, and this in turn allows good, shallow root growth of the corn crop. As a consequence, the uptake of P and K during the first year following meadow is normally satisfactory for no-till corn.
Traditionally, the soil test levels of P and K are often very low in meadow fields; however, following the killing of the meadow with herbicides, the root and top growth will begin to decay, thereby releasing large amounts of P and K. Thus, little yield response can be demonstrated from the use of fertilizer the first year after meadow. It is advisable to take another soil test at the end of the first year so that the fertilizer needs can be established for the second year of corn.