Published in J. Environ. Qual. 34:164-173 (2005).
© ASA, CSSA, SSSA
677 S. Segoe Rd., Madison, WI 53711 USA
Manure Management Effects on Grass Production, Nutritive Content, and Soil Nitrogen for a Grass Silage–Based Dairy Farm
Lynn M. VanWieringena,
Joe H. Harrisona,*,
Tamilee Nennicha,
Debra L. Davidsona,
Lloyd Morgana,
Shulin Chenb,
Mike Buelerc and
Floyd Hoisingtond
a Department of Animal Sciences, Washington State University, 7612 Pioneer Way East, Puyallup, WA 98371
b Department of Biological Systems Engineering, Washington State University, Smith Hall, Pullman, WA 99164-6120
c Bueler Dairy Farm, 8626 Lowell Larimer Road, Snohomish, WA 98296
d Dari-Tech Services, 11730 SE 277th Place, Kent, WA 98031
* Corresponding author (jhharrison{at}wsu.edu)
Received for publication February 18, 2004.
 |
ABSTRACT
|
|---|
Legislation in the United States has recently focused on improving water quality by establishing management practices that limit the quantities of nutrients entering the water supply. Timely application and quantification of the amount of manure applied throughout the grass-growing season can reduce the loss of nutrients into ground or surface water while improving the quality and quantity of grass harvested. During the 2001 and 2002 growing seasons, we measured the effects of different manure application rates on grass yields, grass nutritive value, and soil chemistry on a dairy farm. On-farm estimates of manure N were combined with yield estimates and forage quality measures to evaluate the effects of varying levels of manure application. Yield estimates, N content of grass, and the amount of N in soil and manure were monitored at each cutting for plots amended at different manure application rates. There are three major outcomes of this evaluation: (i) new grass seedings were at higher risk of elevated levels of nitrate N in forage; (ii) increased forage nitrate N at harvest was associated with malfermented silage and increased levels of ammonia N, which resulted in less efficient use of metabolizable protein for milk production; and (iii) increased understanding of N cycling between manure, soil, and plant provided an opportunity to reduce purchased fertilizer.
Abbreviations: CP, crude protein • CPM, Cornell–Penn–Minor
|
INTRODUCTION
|
|---|
NUTRIENT MANAGEMENT, particularly manure management on dairies, has been a focus of legislation in Washington State over the past decade. After several unsuccessful attempts in the early 1990s to encourage dairy producers to voluntary adopt practices to prevent manure from negatively affecting water quality, the Dairy Nutrient Management Act (RCW 90.64) was promulgated in 1998. Passage of the act was influenced by the partial closure of Portage Bay shellfish beds on the Lummi Indian Reservation in 1996 (Boggs et al., 2002). Both surface and ground waters are regulated resources in Washington State.
The Dairy Nutrient Management Act required producers to develop approved nutrient management plans by July 2002, and have the plans certified as fully implemented by December 2003. Dairies that qualify as concentrated animal feeding operations (CAFO) are required to have a nutrient management plan that addresses N and phosphorus by December 2006. The practices used in the nutrient management plans were to meet the standards, specifications, and methods described in the USDA Natural Resources Conservation Service (NRCS) Field Office Technical Guide (USDA, 2004). One conservation practice standard that serves as the major basis of the Nutrient Management Plan is NRCS Nutrient Management 590. In Washington State, the 590 standard requires a fall soil test for nitrate evaluation (Sullivan, 1994). The fall soil nitrate test is intended to provide an evaluation of the past season's N management, rather than to predict how much fertilizer is required the next spring.
The concept of a nutrient management plan was new for many dairy producers, as was the practice of taking soil samples in the fall to evaluate N management during the previous growing season. Producers and their advisors needed education about the value of the management plans and how to correctly implement the fall soil sampling. The requirement provided an opportunity to evaluate the interrelationship of N behavior in the manure, plant, and soil system on a dairy farm in western Washington. The goal of this project was to evaluate years of farm data from five grass fields. On-farm research studies have improved the understanding of nutrient management at the farm or larger scale and the effect of this management on the environment (Bacon et al., 1990; Harter et al., 2002; Hutson et al., 1998; Klausner et al., 1998; Wang et al., 1999).
A uniqueness of our evaluation is the focus on temporal relationships at 4-wk or lesser intervals to characterize the N behavior among manure, soil, and forage systems. The multiyear evaluation of N management, with the goal of more precisely managing N application for grass production, began in 2001. Historical forage quality information from this farm indicated that an opportunity existed to achieve higher levels of crude protein (CP) in grass silage, thus decreasing on-farm import of N.
The primary specific objective was to determine the effects of liquid manure applications on the CP and nitrate content of grass silage. A secondary objective was to determine the effects of additional manure application on soil nitrate concentrations as affected by the time of soil sample collection throughout the year with an emphasis on the fall period.
|
MATERIALS AND METHODS
|
|---|
The dairy operation used in this evaluation was located in western Washington and lactating dairy cattle diets were based on grass silage. The forage was intensively managed for six or seven cuttings per year. The Holstein herd milk production average at the initiation of the evaluation was approximately 13000 kg yr–1, a high level of milk production for Holstein dairy cows. The dairy producer's management practices were to harvest "old-seeding" grass for silage (grass that was not planted in the current harvest year) approximately every 28 d and to harvest "new-seeding" grass for silage (grass that was planted in the current harvest year) every 21 d. Within 10 d after each cutting, liquid manure was applied to the grass fields with a self-retrieving irrigation system at an application rate of approximately 126945 L ha–1. No manure was applied before first cutting.
Manure Application Evaluation
The producer wanted to increase the CP content of the old-seeding grass. Therefore, in 2001, a study was designed to evaluate the potential to increase CP content in grass silage by applying manure in excess of previous practices (previous practice was to apply manure at approximately 126945 L ha–1 after each cutting).
Perennial ryegrass (Lolium perenne L.) and orchardgrass (Dactylis glomerata L.) were planted at 39.2 and 2.24 kg ha–1, respectively, in the spring of 2000 in a 15.8-ha field at the dairy. Data collection for this demonstration project began in 2001, and the grass forage was harvested for silage seven times throughout the growing season starting on 25 Apr. and concluding on 3 Oct. 2001. The 15.8-ha field was divided into three sections, and three different manure application schedules were established. The treatments were not replicated. The treatments were: (i) control; (ii) 2x rate, three times; and (iii) 2x rate, four times. All treatments received a 1x manure application after all seven cuttings in 2001 at 126945 L ha–1. The 2x rate, three times treatment received an additional application of manure after Cuttings 4, 5, and 6, and the 2x rate, four times treatment received an additional application of manure after Cuttings 3, 4, 5, and 6. The additional application of 2x rate, three times resulted in an additional 128.7 kg ha–1 of manure ammonia N applied over the growing season. The additional application of 2x rate, four times resulted in an additional 205.3 kg ha–1 of manure ammonia N applied over the growing season. Manure from the storage lagoon on the dairy was applied using a self-retrieving irrigation system. Water was added to the lagoon periodically throughout the growing season to provide enough liquid for irrigating the crops.
Quality and Quantity of Old Seeding versus New Seeding Grass Silage
Another evaluation was conducted in tandem with the manure application evaluation in 2001. A significant portion of the dairy producer's grass acreage was reseeded annually because the quality and quantity of the grass stands diminish rapidly after the second year. Therefore, two distinctly different grass forages (old and new seeding) were harvested throughout the growing season. Quality and quantity differences between new- and old-seeding grass stands were measured. The intent was to determine if alternative management strategies should be adopted.
Five fields were included in the old- versus new-seeding evaluation in 2001. Fields 1a, 2, and 3 were old seeding, and Fields 4 and 5 were new seeding. Field 1a data were included in both the manure application evaluation and old- versus new-seeding evaluation. Field 2 was a 15.8-ha field planted in 1999. Field 3 was a 17.8-ha field planted in 2000. Fields 4 (28.8 ha) and 5 (25.9 ha) were planted in the spring of 2001.
Old Seeding versus New Seeding Evaluation in 2002
Data collection was continued into 2002 to evaluate trends in N management over time. Of particular interest was the effect of tilling old-seeding grass and replanting on soil nitrate concentrations and new-seeding grass nitrate concentrations over the 2002 growing season.
A second year of data (similar to that collected in 2001) was collected in 2002 on Fields 1a, 1b, 1c, 2, 4, and 5. An additional field (Field 6) was planted into grass in 2002. The seeding rate for the fields that were reseeded in 2002 (Fields 2 and 6) was 1.12 kg ha–1 ‘Penlate’ orchardgrass and 42.8 kg ha–1 ‘Citadel’ ryegrass.
Nutrient Content in Grass Silage and Lactating Dairy Cow Rations
Nutrient analyses of grass from (i) one of the old-seeding grass fields after it had been ensiled, (ii) one of the new-seeding grass fields after it had been ensiled, and (iii) a malfermented silage were sent to a commercial laboratory and analyzed for nutrient content. The nutrient analysis was entered into the Cornell–Penn–Minor (CPM) version of the Cornell Net Carbohydrate Protein System ration evaluator (Fox et al., 1990). Differences in grass silage nutrient profile effects on lactating dairy cattle ration formulation were evaluated. Performance parameters such as predicted milk production, predicted microbial efficiency in the rumen of dairy cows, and predicted milk urea N were also monitored using CPM. The evaluation demonstrated how common differences observed in grass silage quality on a dairy farm in a given year could affect lactating dairy cattle nutrition and performance characteristics. The malfermented silage was included in the evaluation because it is a situation that occurs occasionally in real-world situations. It is not uncommon for producers to incorporate malfermented silage into lactating dairy cattle rations at a reduced feeding rate. The theory is that it is better to feed the silage instead of disposing of the silage. Feeding the silage can have negative implications to the lactating dairy cow.
Three samples of grass (old seeding, new seeding, and malfermented) were obtained after fermentation in the silo for >60 d. These samples were used to evaluate differences in ration formulation and predicted performance characteristics observed in feeding lactating dairy cattle grass silage of differing nutrient content grown and harvested on the dairy during the same growing season. The grass silage samples were dried and ground to pass a 1-mm screen using a Wiley mill (Arthur H. Thomas, Philadelphia, PA). Tissue was analyzed for dry matter (adapted from Goering and VanSoest, 1970), ash (AOAC International, 1990), CP (AOAC International, 2000), ammonia N (Kjeltec Auto 1030 Analyzer; Tecator Foss, Eden Prairie, MN), nitrate (AOAC International, 1990), soluble crude protein (Krishnamoorthy et al., 1982), neutral detergent fiber (NDF) (Mertens 2002), acid detergent fiber (ADF) (AOAC International, 1990), lignin (Goering and Van Soest, 1970), volatile fatty acids (Shimadzu [Kyoto, Japan] GC-14A gas chromatograph and Supelco [Bellefonte, PA] column packed with Carbowax 20M8), and lactate (Model 2700 Select biochemistry analyzer; YSI, Yellow Springs, Ohio). Wet samples of grass silage were also analyzed for pH (DL 12 titrator; Mettler-Toledo, Columbus, OH).
Data Collection and Analysis
The same procedure was used to measure grass yield and N content, soil N, and manure application in all evaluations. One to eight days before harvest of each cutting, grass yield was estimated on each of the three plots by randomly clipping four 0.608- by 0.608-m squares of forage. The forage from each square was dried and weighed to estimate dry-matter yield. Yield estimate samples were composited by treatment for each cutting and N (AOAC International, 1990) and nitrate (AOAC International, 1990) were measured on the composited sample. Soil samples were taken for each treatment 1 to 8 d before harvest of each cutting and analyzed for soil nitrate [Gavlak et al. (2003) for soil nitrate nitrogen determination method and Keeny and Nelson (1982) for extract method]. Field manure application rates were calculated by measuring the volume of manure present in three 18.9-L buckets randomly placed under a self-retrieving irrigation system. Collected manure was analyzed for total and ammonia N via the Kjeldahl procedure (AOAC International, 1990).
Nitrogen available for crop uptake was calculated by summing commercial fertilizer N, 50% of the manure ammonia N [see Table 11-6 in USDA Soil Conservation Service (1992)], and estimated soil N available. A portion of the manure ammonia N will volatilize before it reaches the crop. Volatilization losses were not measured in this evaluation, therefore an estimate from Table 11-6 in USDA Soil Conservation Service (1992) was used. Fields in this study had received manure for many years, therefore it was assumed that there was a buildup of organic matter in the soil. The amount of available soil N was estimated at 22.4 kg N ha–1 yr–1 for each 1% organic matter in the soil, and was based on grass N uptake studies conducted in western Washington (Cogger et al., 2001; Sullivan et al., 2000).
|
RESULTS AND DISCUSSION
|
|---|
Manure Application Evaluation
Cumulative average quantities of N available to the crop and N harvested in grass silage were estimated after each cutting for the three treatments (Fig. 1)
. Soil nitrate levels before each cutting were also plotted (Fig. 1). The amount of manure ammonia N applied per hectare over the growing season increased for the 2x rate, three times treatment and for the 2x rate, four times treatment by approximately 128 and 205 kg of ammonia N ha–1, respectively, and increased N harvested in the grass crop. The amount of N harvested over the growing season increased by approximately 9 kg ha–1 for the 2x rate, three times treatment, and increased by approximately 80 kg ha–1 for the 2x rate, four times treatment. Soil nitrate levels tended to be greater (than the control treatment) by the last cutting for the 2x rate, three times treatment, and were greater during the last three cuttings for the 2x rate, four times treatment. The increase of soil nitrate levels with the extra manure applications indicates that some of the additional N from the manure was not being utilized by the grass.
View larger version (28K):
[in this window]
[in a new window]
|
Fig. 1. Soil N availability, soil nitrate, and forage total N of grass treated with (a) one application of manure after each cutting, Field 1a in 2001 (old seeding); (b) two applications of manure, three times, Field 1b in 2001 (old seeding); and (c) two applications of manure, four times, Field 1c in 2001 (old seeding).
|
|
Forage nitrate N and CP also began to accumulate in the grass for the 2x rate, four times treatment compared with the control (Table 1). At Cuttings 4 and 5, the CP concentrations were 4.2 and 4.6% units greater for the grass from the 2x rate, four times treatment compared with the control (Table 1). Forage nitrate N was 4.5-fold greater in Cutting 4 and 10-fold greater in Cutting 5 than the control plots for the 2x rate, four times treatment (Table 1).
Dry-matter yields tended to increase with additional manure applications even though nitrate N accumulated in the soil (Table 1). Over the entire growing season, there was a 3% increase in yield for the 2x rate, three times treatment (Table 1). The increased yield was even greater (12%) for the 2x rate, four times treatment (Table 1). The greater yield benefit of the 2x rate, four times treatment versus the 2x rate, three times treatment may have resulted from two factors: (i) the increased amount of N and other nutrients added to the crop (an additional 128 kg manure ammonia N ha–1 for the 2x rate, three times treatment and an additional 205 kg manure ammonia N ha–1 for the 2x rate, four times treatment); and (ii) earlier N addition in the growing season when there was a greater potential for additional growth.
Dry-matter yields were measured on 11 Dec. 2001 to evaluate the amount of growth that occurred over the fall after the last cutting. There were 70 d of growth between the last cutting and the grass yield estimates in December. The plots that received extra manure (2x manure, three times = 1.03 Mg dry matter ha–1 and 2x manure, four times = 0.90 Mg dry matter ha–1) during the growing season had greater yields over the fall than the control plot (0.67 dry matter Mg ha–1). These results suggest that there is some growth during the fall, and the plots receiving additional manure during the 2001 growing season achieved greater grass production through the fall. The ability of the grass to grow through the fall indicates that some of the N from the soil is available in the nitrate form even when decreasing soil temperatures limit N mineralization and heavy fall rainfall should have flushed available nitrate away from the root zone.
Quality and Quantity of Old Seeding versus New Seeding Grass Silage
Crude Protein and Nitrate Concentration in Fresh Grass Silage
Cumulative amounts of N harvested in the new-seeding grass fields (Fig. 2)
were greater than or equal to N amounts harvested in the old-seeding grass fields (Fig. 1a), despite 8 to 10% smaller yields from the new-seeding fields than the old-seeding fields (Tables 1 and 2). Cumulative N harvested from the new-seeding grass fields increased because grass CP concentrations in the new-seeding grass fields exceeded CP concentrations in the old-seeding grass fields (Tables 1 and 2).
View larger version (27K):
[in this window]
[in a new window]
|
Fig. 2. Soil N availability, soil nitrate, and forage total N of grass treated with one application of manure after each cutting in Fields (a) 4 and (b) 5 during 2001 (new seeding).
|
|
Soil nitrate concentrations were generally greater in the new-seeding grass fields than the old-seeding grass fields (Fig. 1a and 2). This occurred even though N available from manure, commercial fertilizer, and soil organic matter for the new-seeding fields was less than or equal to the old-seeding grass field (Fig. 1a and 2). Forage nitrate N levels were also greater in the new-seeding grass (Table 2) than the old-seeding grass (Tables 1 and 2). Forage nitrate N concentrations tended to increase with successive cuttings through August for the new seeding (Fig. 3)
.
Increases in soil and forage nitrate concentrations in the new-seeding fields compared with the old-seeding fields may have resulted from increased N mineralization in the soil due to tilling. Microbial activity in the soil increases when soil is tilled. One of the results of increased microbial activity is increased N in the nitrate form. Therefore, new-seeding grass does not need additional N from commercial fertilizer in fields that have received manure for many years. In addition, nitrate N is the form of N that plants readily take up. Nitrate is not toxic to the plant. However, it can lead to health and production problems for lactating dairy cattle when fed at high levels (especially if there is no adjustment period before feeding forages with high levels of nitrate). Therefore, applying high levels of commercial N fertilizer in the spring on fields that have received manure for many years can increase the risk for nitrate accumulation in the plant during the first few cuttings. This higher nitrate concentration in the grass can be of concern when balancing rations for lactating dairy cattle.
The CP and nitrate N concentrations of fresh grass samples before each cutting are plotted in Fig. 4
. As the CP content increased, forage nitrate N also increased (Fig. 4). New-seeding grass tended to accumulate nitrate N to a greater extent than old-seeding grass (Fig. 4b). From an animal health and production standpoint, it is important to note that as the CP levels in grass increase above 21%, there is potential for more nitrate accumulation in the grass plant. Therefore, it is important to have new-seeding grass silages above 21% CP analyzed for nitrate before balancing dairy cattle diets.
View larger version (30K):
[in this window]
[in a new window]
|
Fig. 4. Crude protein (CP) concentration versus nitrate N levels for all grass samples in (a) 2001 and (b) 2002 separated by new- and old-seeding grass.
|
|
New Seeding versus Old Seeding Evaluation in 2002
In 2002, the new-seeding fields (Fields 2 and 6) were compared with the old-seeding fields (Fields 1a, 1b, 1c, 4, and 5; Table 3). Field 2 was reseeded from grass in 2001 to grass in 2002, and Field 6 was reseeded from corn in 2001 to grass in 2002. In 2002, similar trends were observed for increased N harvested in new- (Field 2) versus old-seeding fields (Table 3) when compared with observations from 2001. This was due to higher CP concentrations in the new-seeding grass than the old-seeding grass (Table 3).
Forage nitrate N concentrations were also greater in the new-seeding grass compared with the old-seeding grass in 2002 when Field 2 had been reseeded from grass in 2001 to grass in 2002 (Table 3). Soil nitrate concentrations also tended to be greater from 8 July through 1 Sept. 2002 in the field that had been grass in 2001 and was reseeded into grass in 2002 (Field 2) than an old-seeding grass field (Fig. 5)
. Tilling grass sod in the spring tends to increase N mineralization rates in the soil during the following growing season. The increased levels of nitrate N in the grass and soil in the new-seeding field that had been tilled out of grass sod (Field 2) compared with old-seeding fields (Fields 1a, 1b, 1c, 3, 4, and 5) is probably due to increased organic N mineralization in the soil due to tilling. This observation allows the opportunity to understand N cycling between the manure, soil, and plant, which allows for reduced import of N in the form of commercial fertilizer on fields that have been tilled out of grass sod.
Nutrient Content in Grass Silage
Three silages from the grass harvested in 2001 and 2002 were analyzed for many nutrients important in dairy cattle ration balancing. The three samples consisted of grass silage from an established grass stand (old seeding planted in 2000 and 2001), grass silage from a new seeding (planted in spring 2002), and malfermented grass silage. The new-seeding grass silage had a greater CP concentration (27.1%) than the established stand of grass silage (16.9%; Table 4). However, the other protein fractions (soluble CP and ammonia N) were similar between the new and old seeding (Table 4). High protein in the new seeding can be an indication of high nitrate concentrations in the forage, as was the case in this comparison (Table 4). Acid and neutral detergent fiber and lignin concentrations were lower in the silage of new-seeding grass compared with the old seeding (Table 4). The lower lignin suggests a lower stem to leaf ratio in the new seeding than in the old seeding. Sugar levels (not measured) in the new-seeding silage were inferred to be greater than the old-seeding silage because the lactic acid concentration was greater in the new-seeding grass silage (Table 4). Lactic acid–producing bacteria consume sugar in the forage to make lactic acid as an end product. More sugar present in the grass provides more energy for the lactic acid–producing bacteria.
The malfermented forage showed the classical characteristics of a forage that had undergone a clostridial fermentation. The dry matter content was <30% (Table 4), which provides an environment for clostridial bacteria to grow (McDonald et al., 1991). The ash content was also higher than that of the other grass silages (Table 4), which suggests some soil contamination in the forage when it was ensiled. Clostridial bacteria can live in the soil, and therefore the soil may have inoculated the forage with clostridial bacteria. The high pH and ammonia, acetic acid, and butyric acid concentrations (Table 4) and low lactic acid concentration also suggest a clostridial fermentation (McDonald et al., 1991).
Nutrient Content in Lactating Dairy Cow Rations
The differences in nutrient profile of the three grass silages described in the preceding section deserve attention when feeding lactating dairy cattle. If the differences in quality are not accounted for when switching from one grass silage type to another, performance characteristics such as milk production can be affected. In the following section, two scenarios were used to evaluate the grass silages in the Cornell–Penn–Miner (CPM) version of the Cornell Net Carbohydrate Protein System (Fox et al., 1990) ration evaluator. The results from the two scenarios summarize how ration formulation is affected by grass silage quality, and the effect that forage quality can have on lactating dairy cow performance characteristics.
In the first scenario, three forages were entered into the CPM ration evaluator as part of a typical diet fed to high-producing lactating dairy cattle on the dairy farm in this evaluation. The exercise was conducted to evaluate the effect of not adjusting lactating dairy cow diets when grass silage of substantially different nutrient content was replaced in the ration on the effect of dairy cow performance indicators. The grass silage represented 15% of the diet on a dry-matter basis, and the forage to concentrate ratio was 39:61. Other forages included corn silage (approximately 9% of diet dry matter) and alfalfa hay (approximately 14.6% of diet dry matter). The major ingredients in the concentrate mix included flaked corn, beet pulp, corn distillers, soybean meal, whole cottonseed, and canola meal.
The CP concentration of the diet was 1.6 percentage units greater for the diet containing the new-seeding grass silage compared with the diet containing the old seeding of grass silage (Table 5). The greater CP concentration in the diet increased the metabolizable protein and the amount of peptides and ammonia present in the rumen (Table 5). In turn, the efficiency of using metabolizable protein for milk protein synthesis decreased (Table 5). Both diets contained excess protein, but the diet containing the new-seeding grass silage was in greater excess. Microbial protein production and efficiency of microbial protein production were slightly lower for the diet containing the new seeding also (Table 5). Only carbohydrates and products of carbohydrate fermentation provide energy at rates sufficient for growth of most ruminal bacteria. Therefore, the amount of protein derived from bacteria depends primarily on the amount and fermentability of feed carbohydrates. The lower microbial protein synthesis and efficiency (Table 5) may be due to the slightly lower fermentability of carbohydrates in the diet containing the new compared with the old seeding.
The additional CP content of the new-seeding silage diet was in excess of the dairy cow nutritional requirements for CP and was not needed. This was demonstrated by increased urea cost and milk urea N concentrations (Table 5). Urea is formed by animals during metabolism and circulates through the body. It takes energy to convert feed CP to urea. Therefore, when CP is fed in excess of an animal's nutrient requirements it takes additional energy to process the extra feed CP into urea, and the additional urea is excreted in the urine unused by the animal. Predicted milk urea N concentrations were also elevated in the animals fed diets containing new-seeding grass silage (Table 5). This is another indication that CP was overfed, and the increased levels of CP in the new-seeding grass silage were not needed.
The diet containing the malfermented grass silage did not have a CPM nutrient profile that differed greatly from the diet containing the old seeding of grass silage. Microbial CP yield was lower, but that was mainly due to lower fermentable carbohydrates (Table 5). Metabolizable protein allowable milk was also approximately 0.9 kg different between rations (Table 5). However, feeding malfermented grass silage at 15% of the diet dry matter would cause many problems with health and production in the dairy cow (Erdman, 1993, p. 210–219). Thus, visual observation of the forages being fed is important. The clostridial grass silage became suspect by sight and smell. The silage was sent to a laboratory for a silage fermentation profile, which confirmed that the forage had probably undergone a clostridial fermentation.
In the second scenario, three diets were optimized for each of the three grass silages, and all of the nutrient constraints within the CPM optimization program were met. This exercise was conducted to evaluate the feeding of grass silages of different nutritional value on dairy cow production indicators when the diets were balanced to meet the nutrient requirements of animals before being fed. The three diets tended to have similar nutrient profiles and microbial protein production (Table 6). The biggest difference between the three diets was the forage to concentrate ratio. The diet containing the malfermented grass silage required a higher level of concentrate (forage to concentrate ratio = 40:60) compared with the other diets (forage to concentrate ratio = 53:47; Table 6). This suggests that more concentrate had to be fed to compensate for the poor-quality forage.
The amount and type of protein present in grass silage affects protein balance and excretion in the dairy cow. It is important to be aware of the amount of CP as well as the amount of soluble CP, ammonia N, and nitrate N present in the grass silage when balancing a ration. Overfeeding protein leads to excess N excreted in the urine, which has negative environmental implications and represents an energy cost to the animal. When soluble N and ammonia N are overfed there is less efficient use of metabolizable protein for milk synthesis, and when nitrate N is overfed it can be a health risk for the animal (Erdman, 1993, p. 210–219).
|
CONCLUSIONS
|
|---|
Two key outcomes were evident from this evaluation: (i) nutrient management at the whole-farm or field level requires the integration of a diverse set of management considerations and an understanding of the temporal changes that occur in the soil–plant–manure nutrient interface, and (ii) having a management plan in place that includes the collection of qualitative and quantitative information is key to making sound management decisions. Specific conclusions are:- Additional manure application increases CP content and dry-matter yield in grass silage. However, timing of manure application appears to be more important to achieving a dry-matter yield response than amount of manure applied.
- New-seeding grass probably does not need commercial N fertilizer if the soil has historically been amended with manure.
- New-seeding grass will more likely have a higher level of nitrate N than old-seeding grass.
- Malfermented and high CP grass silages create a challenge for achieving a balanced ration because when soluble N and ammonia N are overfed there is less efficient use of metabolizable protein for milk synthesis, and when nitrate N is overfed it can be a health risk to the animal.
- Understanding the N cycling between the manure, soil, and plant provides the opportunity to utilize N available to the crop more efficiently.
|
REFERENCES
|
|---|
- AOAC International. 1990. Official methods of analysis. 15th ed. AOAC Int., Arlington, VA.
- AOAC International. 2000. Official methods of analysis. 17th ed. AOAC Int., Arlington, VA.
- Bacon, S.C., L.E. Lanyon, and R.M. Schlauder, Jr. 1990. Plant nutrient flow in the managed pathways of an intensive dairy farm. Agron. J. 82:755–761.[Abstract/Free Full Text]
- Boggs, G., D. Raggsdale, S. Hood, and J. Friemund. 2002. Nooksack river water quality and Portage Bay shellfish. USEPA Region 10, Seattle.
- Cogger, C.G., A.I. Bary, S.C. Fransen, and D. Sullivan. 2001. Seven years of biosolids versus inorganic nitrogen applications to tall fescue. J. Environ. Qual. 30:2188–2194.[Abstract/Free Full Text]
- Erdman, R.A. 1993. Silage fermentation characteristics effecting feed intake in silage production. Northeast Reg. Agric. Eng. Serv., Ithaca, NY.
- Fox, D.G., C.J. Sniffen, J.D. O'Connor, J.B. Russell, and P.J. Van Soest. 1990. The Cornell net carbohydrate and protein system for evaluating cattle diets. Part 1: A model for predicting cattle requirements and feedstuff utilization. p. 7–83. In Search: Agriculture no. 34. Cornell Univ. Agric. Exp. Stn., Ithaca, NY.
- Gavlak, R., D. Horneck, R.O. Miller, and J. Kotuby-Amather. 2003. Soil, plant, and water reference methods for the western region. 2nd ed. North American Proficiency Testing Program.
- Goering, H.K., and P.J. Van Soest. 1970. Forage fiber analyses (apparatus, reagents, procedures, and some applications). Agric. Handb. 379. USDA-ARS, Washington, DC.
- Harter, T., H. Davis, M.C. Mathews, and R.D. Meyer. 2002. Shallow groundwater quality on dairy farms with irrigated forage crops. J. Contam. Hydrol. 55:287–315.[Medline]
- Hutson, J.L., R.E. Pitt, R.K. Koelsch, J.B. Houser, and R.J. Wagenet. 1998. Improving dairy farm sustainability II: Environmental losses and nutrient flows. J. Prod. Agric. 11:233–239.
- Keeny, D.R., and D.W. Nelson. 1982. Nitrogen—Inorganic forms. p. 674–676. In A.L. Page, R.H. Miller, and D.R. Keeney (ed.) Methods of soil analysis. Part 2. 2nd ed. Agron. Monogr. 9. ASA and SSSA, Madison, WI.
- Klausner, S.D., D.G. Fox, C.N. Rasmussen, R.E. Pitt, T.P. Tylutki, P.E. Wright, L.E. Chase, and W.C. Stone. 1998. Improving dairy farm sustainability I: An approach to animal and crop nutrient management planning. J. Prod. Agric. 11:225–233.
- Krishnamoorthy, U., T.V. Muscato, C.J. Sniffen, and P.J. VanSoest. 1982. Borate-phosphate procedure as detailed in nitrogen fractions in selected feedstuffs. J. Dairy Sci. 65:217–225.[Abstract/Free Full Text]
- McDonald, P., N. Henderson, and S. Heron. 1991. The biochemistry of silage. 2nd ed. Chalcombe Publ., Marlow, UK.
- Mertens, D. 2002. Gravimetric determination of amylase-treated neutral detergent fiber in feeds with refluxing in beakers or crucibles: Collaborative study. J. AOAC Int. 85:1217–1240.[Web of Science][Medline]
- Sullivan, D. 1994. Guide to report card soil testing. Tech. Notes USDA Agron. 35. USDA Soil Conserv. Serv., Spokane, WA.
- Sullivan, D.M., C.G. Cogger, A.I. Bary, and S.C. Fransen. 2000. Timing of dairy manure applications to perennial grass on well drained and poorly drained soils. J. Soil Water Conserv. 55:147–152.
- USDA. 2004. Welcome to eFOTG [Online]. Available at www.nrcs.usda.gov/technical/efotg/ (verified 20 Aug. 2004). USDA-NRCS, Washington, DC.
- USDA Soil Conservation Service. 1992. Waste utilization. Chapter 11. In Agricultural waste management field handbook [Online]. Available at www.info.usda.gov/CED/ftp/CED/neh651-ch11.pdf (verified 20 Aug. 2004). USDA, Washington, DC.
- Wang, S.J., D.G. Fox, D.J.R. Cherney, S.D. Klauzner, and D.R. Bouldin. 1999. Impact of dairy farming on well water nitrate level and soil content of phosphorus and potassium. J. Dairy Sci. 82:2164–2169.[Abstract]
Related articles in JEQ:
- This Issue in Journal of Environmental Quality
JEQ 2005 34: 1-6.
[Full Text]
This article has been cited by other articles:
|
|
|
|
 
G. A. O'Connor, H. A. Elliott, N. T. Basta, R. K. Bastian, G. M. Pierzynski, R. C. Sims, and J. E. Smith Jr.
Sustainable Land Application: An Overview
J. Environ. Qual.,
January 1, 2005;
34(1):
7 - 17.
[Abstract]
[Full Text]
[PDF]
|
|
|
TOP
ABSTRACT
INTRODUCTION
