Manure Utilization in Crop Production

by Glenn Raines, Superintendent, Orr Center

• Introduction
• Procedures
• Findings
• Table 1
• Table 2
• Table 3
• Summary Points

Introduction:

Swine production facilities in Western Illinois consist of basically three types: a) Small operations with individual "pig huts," with animals on pastures or open lots, b) Medium sized confinement operations with a lagoon and/or under-facility manure storage, and, c) Large operations with lagoons and/or above ground manure storage facilities. Effluent accumulation from b and c operations dictates land application and generally at very high effluent rates.

Eighteen years ago, the confinement pit manure storage method was used extensively and the continued application of high quality manure had not been thoroughly researched. This study investigates the effects of swine effluent on corn and soybean yields, as well as, the buildup of nutrients within the soil profile. Grain yields and fall soil samples help ascertain the effects of the effluent. Laboratory analyses of the applied effluent help determine nutrient application and potential soil buildup of the essential nutrients.

Procedures:

A long term swine effluent study (corn and soybean rotation) with effluent rates of 0, 2000, 4000, and 8000 gallons per acre, along with a Conventional Fertilizer (CF) rate is used to monitor the crop's response to injected swine effluent. The Conventional Fertilizer rate is nutrient equivalent to the 8000 gal/A rate of effluent. The effluent is obtained from a swine confinement pit area, agitated for uniform consistency and injected to a depth of nine inches in the spring. The injection slots are positioned on 45 inch centers, creating a pattern where certain rows planted on 30 inch centers will be equidistant from the knife slot and certain rows will be planted directly over the knife slot. Corn or soybeans are planted in 30 inch rows in a timely manner with all other cultural practices performed as needed. Grain yields are recorded.

Soil samples are collected following harvest from both the row area and from between the row area (a treated and a non-treated area).

Findings:

Both corn and soybeans yield very well when grown with injected swine effluent as the sole source of fertilizer. Grain yields have fluctuated from year to year, and differences are seen with respect to the location of the effluent and the position of the crop's row. The 7-year average corn yields indicate that 2000 gal/A - Under Row placement produced the highest yields. As rates increased, effluent placement was more of a factor in yield depression due to the increased quantity of nutrients and higher amounts of salt.

The soybean yields have been fairly uniform regardless of the rate of effluent. Slight yield advantages are seen for the Between Row placement at the higher rates. The 4000 gal/A rate appears to produce the highest yields.

Effluent analyses indicate some variability through the years, however, the long term average is very near those values published by other agencies.

Soil analyses have indicated pH levels are basically being maintained due to the relatively high pH of the effluent. Soil test P₁ levels increase dramatically with increased effluent rates. The fall 1998, 8000 gal/A treatment, Between Row placement samples were 206, 198 and 56 lb/A P₁ respectively for sampling depths of 0-8, 8-16, and 16-24 inches. Some downward movement of nutrients is seen at the 16-24 inch depth, however, the concentration is less than one would expect considering that the same treatments have been applied for 18 years.

Table 1. Corn yields in the swine effluent study. Crop years (7)

C.F. = Conventional Fertilizer (240 lbs N - 180 lbs P₂O₅ - 240 lbs K₂O)

Table 2. Soybean yields in the swine effluent study. Crop Years (5)

C.F. = Conventional Fertilizer (240 lbs N - 180 lbs P₂O₅ - 240 lbs K₂O)

Table 3. Manure analysis, swine effluent study. (TKN) Soluble

Summary Points:

• Liquid swine effluent is a good source of fertilizer nutrients.

• For maximum utilization of nutrients, the material must be injected.

• No additional fertilizer is required for corn production when adequate rates of effluent are utilized.

• Corn is more sensitive to manure directly under the row than between the rows.

• Corn is more responsive to lower rates of manure than higher rates.

• Corn yields were higher at the 2000 gal/A under row than the 8000 gal/A between row placement.

• Soybeans were slightly more responsive when manure was placed between the rows.

• Soybean yields were fairly uniform regardless of rate.

• The salt index of crops should be considered when applying high rates of effluent.

• Soil pH levels are generally maintained due to the relatively high pH of the manure.

• Most of the phosphorus contained in the effluent is remaining in the 0-8 inch soil layer.

• Soil organic matter does not appear to increase as effluent rates are increased.