Wheat Response to Lime on Acid Soils

Chapter 6 – Fertility, No. 11, Spring 1987

Roger Veseth

Increasing acidity in the surface foot of soil is reducing yield potential of cereal and legume crops in northern Idaho and other Northwest cropland areas. Recent research has shown that lime (calcium carbonate) applications can increase yields of winter wheat and spring wheat if the soil pH is less than 5.3. The research has been conducted by Robert Mahler, University of Idaho soil scientist, in cooperation with Robert McDole, UI Extension soil specialist.

The demand for agricultural lime is new to much of this region and commercial supply options are limited, Consequently, lime is often expensive and difficult to obtain. Equipment capable of spreading solid (dry) lime is also often a limiting factor. Dry fertilizer applicators are not capable of spreading lime materials because they contain a range of particle sizes and because of the high application rates required.

Liquid lime may be an option because most producers have the spray equipment needed for application. However, there are several limitations to the use of liquid lime as well, The high application rates required (120 to 240 gallons per acre) may limit the feasibility of using sprayer equipment. Other limitations include the higher cost of liquid lime material compared to dry lime, extra cost of preparing the liquid lime (a suspension) and the higher cost of transportation due to the fact that liquid lime is 50 percent water.

4-Year Research Effort

Mahler completed 4 years of research from 1983 through 1986 directed at: (1) evaluating the effect of liquid lime on yields of spring wheat and winter wheat, (2) determining the optimum timing and placement of liquid lime and (3) comparing the effectiveness of liquid lime to a typical solid lime material. The research was conducted east of Moscow in a 22- to 24-inch precipitation zone on silt loam soils. Initial saturated paste pH of the soil was 5.1.

Liquid Lime Application Rate and Timing

Yield response of spring wheat and winter wheat to three rates of liquid lime broadcast and incorporated 5 months before planting was compared with the same applications 2 days before planting, The lime used in the liquid suspension had a neutralizing value (Calcium Carbonate Equivalent) of 100. The suspension contained 48 percent 200 mesh lime, 50.5 percent water and 1.5 percent suspension clay.

Mahler found that liquid lime applied 5 months before planting at rates of 500 and 1,000 pounds/acre resulted in significant spring wheat yield increases of 50 and 63 percent, respectively (Table 1). The 250 pounds/acre rate, applied 5 months before planting, and all the application rates 2 days before planting did not result in spring wheat yields statistically superior to the check. Mahler points out that this indicates the importance of applying lime in the fall before a spring crop to allow time for the lime to react with the soil and raise soil pH.

Table 1. Yields of spring wheat and winter wheat from plots treated with liquid lime either 5 months before or 2 days before planting at Moscow, ID, In 1983 and 1984 (Mahler, Ul).

With winter wheat, 500 and 1,000 pounds/acre applications of liquid lime 5 months before planting increased yields 21 and 45 percent, respectively. When the same rates were applied 2 days before planting, yield increases were 23 and 34 percent, respectively. The 250 pounds/acre application rate did not significantly increase yield regardless of application date. In contrast to spring wheat, application date was not a factor in winter wheat response to lime. The winter months apparently allow the time necessary for the liquid lime to react with soil, consequently, masking any potential advantage of an earlier application date.

Liquid and Solid Lime Comparison

In 1985 and 1986, Mahler compared five application rates of liquid and solid lime broadcast and incorporated 1 day before planting. The liquid lime contained 48 percent 200 mesh lime, 50 percent water and 2 percent suspension clay. Solid lime had the following particle size distribution: 80 percent passed a 20-mesh sieve, 50 percent passed a 60-mesh sieve and 20 percent passed a 100-mesh sieve. Both sources had a neutralizing value of 100.

Liquid lime application rates of 2,000, 1,500, 1,000, 500 and 250 pounds/acre 1 day before planting resulted in spring wheat yield increases of 25.0, 13.4, 14.4, 11.4 and 11.0 bushels/acre, respectively (Table 2). No significant differences were found between yield responses to liquid and solid lime at any application rate.

With winter wheat, liquid lime application rates produced yields significantly higher than solid lime. Liquid lime applied at rates of 2,000, 1,500, 1,000,500 and 250 pounds/acre resulted in winter wheat yields of 38.8,43.2, 42.7, 27.1 and 15.8 percent greater than the check, respectively. Yield increases with the same application rates of solid lime were only 21.1, 23.5, 9.8, 2.7 and 3.9 percent, respectively. Differences in winter wheat yield between liquid and solid lime were statistically significant at all application rates.

Table 2. Comparison of spring wheat and winter wheat yield responses to liquid and solid lime broadcast and incorporated 1 day before planting near Moscow, ID, in 1985 and 1988 (Mahler, IA)

Incorporation vs. Non-incorporation

Wheat response to 500 and 1,000 pounds/acre rates of liquid and solid lime broadcast and incorporated one day before seeding was compared with broadcast nonincorporated applications 3 days after seeding (Table 3). Differences were generally not statistically significant when comparing application rates of liquid and solid lime on spring wheat and winter wheat yields.

A broadcast non-incorporated option for lime applications could be important in a no-till system. However, in this higher precipitation area, producers are generally not in a continuous no-till system for all crops, so lime could be applied when some tillage incorporation was possible in the rotation.

Conclusions

Mahler’s research conclusions point out some general guidelines for producers considering liquid or solid lime applications.

1. For a spring crop, liquid lime was more effective when applied in the fall than in the spring, allowing more soil reaction time under moist conditions. A similar advantage would be expected with solid lime. For winter wheat, liquid lime application just before planting appears to be about as effective as application the previous spring. Earlier application of solid lime may be advantageous, however.
2. Fall applications of 500 and 1,000 pounds/acre of liquid lime to acid soils (pH 5.1) significantly increased spring wheat and winter wheat yields.
3. When applied in equal amounts, liquid lime usually produced wheat yields superior to solid lime. The difference in yield response can be explained by the fact that finer mesh-size liquid lime has a greater surface area and contacts more soil than solid lime, consequently, neutralizing soil acidity at a faster rate.
4. Even though liquid lime applications were successful in these experiments, the lower cost of solid lime must be considered. When material and application costs are taken into account, liquid lime may be as much as three times more expensive than solid lime.
5. Liquid lime has some advantages that may overcome some of the cost difference. These include: possible use of commonly available spraying equipment; quicker reaction time in the soil and improved yield response; and greater uniformity of application on hilly terrain.
6. Liquid lime at low rates (500 pounds/acre) may give a yield benefit on the crop in the crop year when-applied, but it does not correct the acid soil problem. Thus, it is only a temporary measure.

Table 3. Comparison of spring wheat and winter wheat yield response to broadcast Incorporated and non-incorporated applications of solid and liquid lime near Moscow, ID, in 1985 and 1988 (Mahler, Ul).

Additional information on lime materials and application considerations can be found in the 1986 University of Idaho Current Information Series 787, Lime Materials by Mahler and McDole. It is available through the Extension Office in your county. A new UI Current Information Series, The Relationship of Soil pH and Crop Yields in Northern Idaho, by Mahler and McDole should be available this summer. The increasing availability of lime materials and application equipment in the Northwest should make lime application on acid soils more feasible in the future.