NSCP Research - Project B
Manure Management to Sustain Water Quality
A major contributor of nitrate-N to groundwater is application of livestock manure, even when applications are consistent with the agricultural code of practice. Application of manure in late summer or fall, frequently on sod prior to fall plowing results in excess concentrations of nitrates in the soil during the fall and spring leaching periods. However, it is usually difficult for farmers to apply manure at a time when crop demand for nitrogen is high. Approaches such as manure composting and use of cover crops have potential to convert the N to an organic form and release it for crop use in the subsequent season.
This statement of work is quite specific in its requirements. The technical approach to the problem should be well defined. In light of the short period of funding and the need to produce definitive results within the time frame of this program, the proposal should clearly indicate how the management of manure and the production of a subsequent crop is to be handled. The description of existing or ongoing work which may contribute to a proposal should be given in sufficient detail to permit assessment of the opportunity for success.
The Evaluation of Three Manure Composting Methods for Nitrogen Conservation Environmental Impact, Crop Growth Response and Operating and Maintenance Costs
R. St. Jean - Project Leader
The data collected for the passive aeration, turned pile and forced aeration composts and a control pile of stored manure did not indicate a significant difference in nitrogen volatilization losses between treatments. The losses ranged from 30.1 percent for the passive aeration compost process to 44.4 percent for the control pile of manure. The data did indicate that the three composts and control pile of manure underwent different degrees of stabilization, as indicated by the significant differences in carbon loss. Carbon losses ranged from 18% for the forced aeration compost to 36 percent for the turned pile compost. The data showed a general trend of higher nitrogen losses from the manures which underwent the highest levels of stabilization. The control pile of manure actually showed the highest level of nitrogen volatilization losses, although not statistically significant.
The peat moss cover skin on the passive aeration windrow demonstrated an excellent capacity for nitrogen retention. Nitrogen increased by a factor of 1.87 during the composting process. However, approximately one third of it was in the ammoniacal form and would be very susceptible to loss during handling and spreading of the solid material. It would also require thorough mixing with the compost in order to make effective use of the additional nitrogen. The data indicated that a 50.8 percent reduction in carbon occurred in the cover skin resulting in a concentration of nitrogen to 4.3 percent on a dry matter basis.
It was observed that composting of livestock manures can not be completed under covered conditions without the addition of moisture, to maintain levels above the 45 percent range at which moisture becomes limiting to the biological process. Moisture levels in the finished composts ranged between 21.8 percent for the passive aeration compost to 33.3 percent for the turned pile compost. The three composts and control pile of manure were retained under cover for an 8 to 12 month curing period, irrigated to a 50-60 percent moisture level and mixed to assess their potential for reheating. All materials reheated to active composting temperatures in the 45 to 60 C range, indicating that the rapid biological stabilization activity associated with composting was not complete. The high evaporative capacity of composting manure indicates it has potential as a treatment process for barnyard runoffs and dairy farm milkhouse washwater.
Leachate analysis indicated that the potential for nitrogen loss by leaching was not significantly altered by the composting processes examined. But, the compost with the greatest degree of biological stabilization had the lowest mean nitrogen levels in the leachates, indicating a possible trend. Distilled water leachates contained total Kjeldahl nitrogen (TKN) ranging from a mean of 240 mg/l for the turned pile compost to 399 mg/l for the raw manure used in the composting processes. Differences were not statistically significant, however, composting did result in higher levels of phosphorus in the acetic acid leachates from compost, compared to raw manures. There was no significant difference in phosphorus leaching between treatments in the distilled water leachate.
The crop growth response trials showed a definite trend of more consistent yields from the plots receiving commercial fertilizers compared to all other treatments. However, at least one treatment plot from each of the compost treatments achieved yields equivalent to the fertilizer yields.
There was no significant difference in corn yields between treatments, even at a 75 percent level of confidence. The cold, wet growing season experienced during the plot trial experiment is thought to have confounded the results to some degree, due to the slow rate of nutrient mineralization from organic amendments and potential for denitrification in cold, waterlogged soils.
Corn plants harvested in July for comparison of total plant dry weight and tissue nutrient analysis had higher plant weights for plots receiving compost pre-plant incorporated compared to winter application. Fall harvested grain corn and whole corn plants did not show any significant difference in yields between pre-plant and winter compost applications. Mean grain corn moisture levels were all in the 53 to 55 percent range, indicating that no difference in corn maturity resulted from the various treatments.
The economic comparison indicated that the mechanically mixed forced aeration composting system has the lowest energy requirements at $0.185/tonne of manure composted followed by $0.190/tonne for the passive aeration compost and $0.72/tonne for the turned pile compost. The mechanically mixed forced aeration composting method has no direct labour requirements associated with the process itself. The passive aeration method requires 0.039 hours/tonne followed by the turned pile method with 0.147 hours/tonne. The capital cost estimates indicate that the turned pile and passive aeration composts have similar capital costs of $19,300, for concrete pads and leachate collection and re-distribution systems. The mechanically mixed forced aeration system had the highest capital cost of $80,000, assuming equivalent tonnage capacity.
Manure Management to Sustain Water Quality
University of Guelph
A field experiment was established at the Winchester Research Station of Kemptville College of Agricultural Technology to investigate the fate of nitrogen from cattle manure applied to land previously under alfalfa residues, and the consequences for the quality of water resources. The objective of the program was to evaluate the risk of nitrate leaching from fall-applied manure, and evaluate whether this could be alleviated by timely agronomic practices. Specific practices considered were the use of cover crops, incorporation of straw residues and sowing a winter cereal crop.
The following treatments were imposed and test crops planted.
The liquid cattle manure was injected, and the solid manure applied with a conventional spreader. The soil at this time contained 80 kg ha' mineral nitrogen. Only 5 kg ha-1 of mineral nitrogen was present in the 98 kg N ha-1 from the composted cattle manure, but the liquid manure contained 203 kg N ha-1 as mineral nitrogen.
The experimental program involved the sampling of soil, soil water, and plant material to assess the fate of the nitrogen from the manure, the availability of the nitrogen to crops, and the presence of mineral nitrogen, including the mobile nitrate ion, in the soil.
The cropping history of the chosen site was known, along with information on crop response to N fertilization. This knowledge was considered essential so that information gained at this site would then be moire readily transferable to similar farm systems in other areas of Ontario.
Three periods were identified as crucial for evaluating the agronomic practices. These were the fall, the period of spring runoff, and the main growth stages of the spring sown crop. The results from the field experiment were evaluated for these three periods.
The volumetric water content of the top 100 mm of soil was approximately 0.15 at the time the manure was applied at the end of August. This was ideal for injection, but severely impaired the establishment of the grass. Growth of the winter wheat, oilseed radish, volunteer oats from the incorporated straw, and wild mustard weeds was good in the fall of 1991.
The uptake of mineral nitrogen (y, kg N ha-1) by all crops in the fall was directly related to the dry matter produced (x, t ha-1) according to the equation: y = 0.43x - 10.2 (p < 0.001). By the end of November almost all the mineral nitrogen applied in the manure could be accounted for in the soil and plants. In manured plots there was 55 kg NO3-N ha-1, 78 kg NO3 -N ha-1 in plots that received composted manure, and 134 kg NO3 -N ha-1 in plots given liquid manure. All this nitrogen was at risk of leaching. The winter was cold and the snow cover was ended by heavy rain on January 14, after which the temperature dropped sharply and killed the winter wheat crop.
There was little through drainage in the early spring and all plots contained more mineral nitrogen at planting in May than in November. Two periods of leaching were identified in late spring and early summer. The maximum concentration of nitrate-N recorded in the water draining from the rooting zone for all treatments exceeded the Ontario Drinking Water Objective of 10 mg L-1 during one or both periods.
The Ontario soil nitrogen test suggested that the manured plots would require some fertilizer nitrogen to obtain the maximum economic yield, but all manured plots contained sufficient nitrogen. When the test was repeated at the time for side-dressing corn, nitrate-N had increased by an average 26% for the treatments where nitrogen was immobilized during the fall.
The growth and yield of the corn, and the grain yield of spring barley were largely unaffected by treatment. The yield of barley was influenced by the lodging that took place preferentially on the manured plots. Although earlier in the season nitrogen uptake by barley was greater on manured plots than on plots that received no manure, there was no significant difference at harvest, probably because of the lodging which made sampling difficult.
Nitrogen released by the ploughing of the alfalfa hay soil provided sufficient nitrogen for the corn crop. The total nitrogen in the control treatment at harvest was 150 kg N ha-1. The crop on land injected with liquid manure contained 225 kg N ha-1, but this was not converted into significantly more harvestable yield. About half of the additional nitrogen was present in the grain, but the remainder was in the harvest residues that will contribute to the organic matter pool of the soil and be remineralized in the future. There was more nitrogen in corn crops grown on land where cover crops were grown in the previous fall compared to that in manured controls. However, the increase only occurred after August 20. This indicated that the main period for release of nitrogen from the cover crop residues only took place late in the season. If cereals rather than corn had been the test crop it strongly suggests that most of this nitrogen would have remained in the soil where it would have been at risk of leaching.
Since yields of corn were unaffected by the treatments imposed despite the indications of the soil nitrogen test, it is clear that adjustments are needed when making fertilizer recommendations based on the test to ensure that the nitrogen from crop residues (straw or cover crop) is included. The soil N test, which only takes account of nitrate-N, clearly underestimated the amount of mineral nitrogen available in the soil on all treatments. This was even true for controls where nitrogen from below-ground residues of the alfalfa hay was not adequately assessed. The results indicated that 115 kg N ha-1 was an appropriate credit for the underground residues of the alfalfa hay.
The study strongly indicated that applying liquid manure in the fall was potentially hazardous to water resources. The risk from leaching was high in the fall immediately after application, in the following spring, and in the next fall period, especially if cereals were grown in the spring. None of the fall treatments to immobilize nitrogen were adequate to reduce the risk significantly. Composted cattle manure did not pose a significant hazard in the fall after application, but did so in the fall of the following year.