Research Report 1.4

Transformations in Soil: Crop Response to Nitrogen in
Manures with Widely Different Characteristics

Dr. E. G. Beauchamp, J. Buchanan-Smith and M. Goss,
Department of Land Resource Science, University of Guelph,
Guelph, ONT, N1G 2W1
COESA Report No.:  RES/MAN-004/97

Objectives & Expected Outputs
Executive Summary

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Objectives and Expected Outputs
Objectives: To develop an understanding how the N in manures with different characteristics applied to soil in the field is immobilized or mineralized and released in synchrony with crop N requirement. Soil factors include time of application, soil texture and soil acidity. Manure characteristics include the effects of the protein levels in the dairy rations.
Expected Outputs: Phase 1 - Development of a yield response curve for corn with fertilizer, and comparison with manure N rates;
Phase 2 - Comparison of the mineralization/immobilization and availabilities of N from five different manures following fall and spring applications on one site;
Phase 3 - A laboratory study on the influence of soil texture involving four soils ranging from loamy sand to clay loam;
Phase 4 - A laboratory study involving four soils ranging in soil acidity in which ammonium and NO-3 contents are monitored during incubation;
Phase 5 - using feeding trials and characterization of the manure to develop one or more models for predicting manure N content of manures from animals given different feedstuffs.
Type: Contribution Agreement, University
Spending Profile: 93-94: $28.8 K,  94-95: $118.5 K, 95-96: $117.1 K, 96-97: $118.6 K,  Total: $383.0 K
Status: Available Fall, 1997


Executive Summary

A three-year field and laboratory study was undertaken to obtain a better understanding of the availability of N in manures that vary substantially in several important characteristics.

The manure characteristics focussed on in this study included kinds of manure (animal species), ammoniacal and total N contents, and kind of bedding. A major objective was to determine how these characteristics affect the release or availability of manure N especially during the early season in synchrony with corn crop N requirement. Also studied were fall vsspring applications of manures, the influence of soil acidity on N availability with different manures, and the effects protein level and degradability in the diet of dairy cows on manure N availability.

The research was conducted in five phases briefly as follows.

  • corn crop response to fall- and spring-applied manures on the farms on which they were produced.

  • corn crop response to fall- and spring-applied manures to compare rates of manure N and bedding additions of several manures at the Elora Research Station.

  • corn crop response to residual N from manure and urea applied the previous year

  • a laboratory study to determine the effects of soil acidity and liming on N transformations with several manures

  • a laboratory study to determine the characteristics and availability of N in urine and faeces of dairy cows fed diets varying with respect to protein content and degradability.

The manures studied varied widely with respect to ammoniacal N content and included liquid dairy cattle (LC), solid beef cattle (SC), solid broiler chicken with wood shavings bedding (Pw), solid broiler chicken with straw bedding (Ps), and liquid swine (LS) manures. These manures represent the range of manures commonly produced on livestock farms in Ontario. Different rates of these manures were compared with different rates of urea in field experiments.

It was anticipated that manures with relatively low ammoniacal N content and high C/N ratio (e.g. SC manure) would result in a depression in available soil and manure N early in the growing season. Instead there was little or no increase in available N during this period. With LS manure having a relatively high ammoniacal N content, release of available N occurred well in advance of the major period of N uptake by the corn crop.

The ammoniacal N content of manures was the major determinant of N availability after application. The relative importance of the organic N fraction compared with ammoniacal N in manures could not be ascertained. It was observed that extractable soil inorganic N (nitrate and ammonium) was always less than ammoniacal N applied in manures or urea even within a few days following application in the spring. In some cases, as little as 30 to 40 percent recovery was obtained. This apparent disappearance was probably due to ammonia volatilization, fixation by clay and immobilization by soil microbes. The rates of release of some of this N during the first two months of the growing season were inconsistent from year to year. Where substantial available N was released, it was generally related to ammoniacal N applied with the manure. These differences in inorganic N recoveries coupled with variable release rates in the soil from year to year made it difficult to estimate the contribution of available N from the organic N fraction of manures, or to assess manure N dynamics in the soil involving N mineralization/immobilization.

Applying liquid manure to field plots

Applying solid manure to field plots

Applying liquid manure to field plots

Applying solid manure to field plots

In spite of difficulties in comparing different manures, it appeared that the SC manure behaved differently than the others. Monitoring of soil inorganic N and plant N uptake in the field along with a 15N study in the lab revealed that significant net immobilization of inorganic N occurred during the early part of the growing season. Furthermore, corn grain yields and N composition of mature plants suggested that there was a substantial release of N with the SC manure during the latter part of the growing season that was not evident with the other manures.

There was no clear indication that fall application of solid manures significantly reduced corn crop response compared with spring-applied manures. However, crop response to fall-applied swine manure was decidedly lower than spring-applied manure in two field experiments. Thus, it appears that the efficacy of fall-applied manures may depend on manure characteristics.

The kind of bedding (woodshavings vs straw) in the Pw and Ps manures or the additions of these beddings to SC and LC manures appeared to have relatively little influence on manure N availability.

The rate of nitrification (ammonium to nitrate) was slower in acid soils but increased to a near normal rate when these soils were limed. Other than slowing nitrification rate, soil acidity did not appear to exert any other influence.

The feeding of a diet with high protein content and degradability to dairy cattle resulted in a higher portion of excreted N present in the urine, but with little change in the faeces. Differences in diet had little influence on extractable inorganic N from either urine or faeces treated soil. Virtually all of the urine N was converted to ammonium and eventually to nitrate in soil whereas only a small fraction of faeces N was recovered as inorganic N. There was evidence that the concentrations of extractable inorganic N with the faeces treatment actually decreased during the incubation period. This indicated that the urine fraction of cattle manure contains almost all of the N immediately available to a crop.

It is anticipated that the findings of this study will be used to revise the manure application recommendations for crop production.

This project is related to another project (Proj. # 1.2) entitled "Nitrogen and Carbon Transformations in Conventionally-Handled Livestock Manures" done by Environmental Soil Services. Various C and N characteristics of the manures are examined to a greater extent in that study.



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