Forage Guide for Modern Forage Systems
A Guide to Selecting, Planting, and Managing Forages for Profit by John Kaye

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Introduction

 

I. Forages for Profit

Chapter 1: The Key

Chapter 2: New Pastures

Chapter 3: How to Plant

Chapter 4: When To Plant

Chapter 5: Soil Fertility

Chapter 6: Seeding Rates

Chapter 7:Young Seedlings

Chapter 8: MIG Effectiveness

Chapter 9: Nurse Crops

 

II. Perennial Forages

 

III. Annual Forages

 

IV. Technical Assistance

 

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Modern Forage Systems

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Planting and Managing Forages for Profit

 

Chapter 5: Establishing and Maintaining Soil Fertility

When working with perennial forages, soil fertility is vital because it affects the quality of the forage that the animal eats.  Animal health and production is related to the nutrients the animal receives from the forage. The best way to determine the fertility level and corrective fertilizer requirements of a current or future pasture is from a soil test.  Soil tests tell us the soil pH; nitrogen (N) recommendations; phosphorus (P) and potassium (K) levels and recommendations; as well as secondary and micronutrient status.  For a new pasture, soil tests samples should be collected and analyzed well in advance so the types and quantities of recommended fertilizers can be incorporated into the soil at the time of field preparation.  At this same time, lime should be applied to achieve a soil pH of at least 6.3. (Note:  on a new full cultivation seeding of a field with a pH range of 5.8-6.5, applying 4 tons/ac of lime followed by working it into the soil along with the fertilizer suggested by the soil analysis would not be excessive, followed by an annual top dress of 2 tons/ac.).  In addition to correcting pH, lime is a source of valuable Calcium, which all living things require. To see what effect pH has on utilization of N,P,K and how much is potentially wasted see the chart below.

Fertilizer Utilization Chart. Without the proper pH, fertilizer cannot do its job.  It is imperative that the pH be adequate to limit the amount of wasted fertilizer.  (Source: Chris McCracken, Barenbrug, USA.)
                                         

	% FERTILIZER UTILIZED			% WASTED
SOIL pH	Nitrogen  (N)	Phosphate (P)	Potash  (K)
Extremely Acid 4.5 pH	30%	23%	33%	71.34%
Very strong Acid 5.0 pH	53%	34%	52%	53.67%
Strongly Acid 5.5 pH	77%	48%	77%	32.69%
Medium Acid 6.0 pH	89%	52%	100%	19.67%
Neutral 7.0 pH	100%	100%	100%	0 %

 

NOW YOU SEE WHY SOIL pH IS SO IMPORTANT --$$$$$$$$
(Note:  Nutrients in fertilizers are stated on the labels. The percentage of actual  N, P, and K is expressed as a ratio by weight and in the order of N-P-K. E.g., a 10-10-20 fertilizer contains 10% N, 10% P and 20% K. Thus 100 lbs of this fertilizer contains the actual element (in unit lbs)  of 10 lbs/N, 10lbs/P and 20lbs/K with the remaining 60 lbs being filler. Urea a common form of N is rated 46-0-0 which  yields 46 unit/lbs of N per 100 lbs of fertilizer. )
The pH of the soil is important, but why the pH is what it is, should be considered more important.  The base saturation levels of Calcium, Magnesium, Potassium, Sodium and Hydrogen levels determine the pH.  You can have a high pH and still have a shortage of Calcium in the soil.  Calcium however, is the one element that drives the production of quality forage.  A good source of Calcium is Gypsum, which is Calcium Sulfate.   Sulfur is also very important for creating high quality proteins in forages.  Most soils are low in this element.
All grasses need nitrogen (N) on a periodic basis during the growth cycle to attain and maintain optimum production.  Nitrogen is a consumable fuel just like gasoline is to an engine.  It is consumed daily as the plant grows.  This is true even when grasses are planted with clover or other nitrogen fixing legumes.  Legumes are a money saving source of N especially during the summer and should be used where possible.  Alice white clover can provide up to 150 unit/lbs of N per acre/year.  Even with clover, optimum production still requires about 150-200 unit/lbs. of supplemental N per acre/year.  This assumes that the proper levels of Phosphorus and Calcium are present.  Without these, the performance of N alone is greatly reduced.  Apply 50 unit/lbs of N in the spring as soon as the soil is 50 degrees or warmer, with the remainder applied in 3-4 equal doses throughout the growing season, but not later than mid-September.  N should be applied with moisture, either from irrigation or rain for the best results.  On established pastures, take a soil test every 2-3 years, then top dress on the recommended levels of P and K in the fall, allowing winter action to incorporate.

Persistency of forages is related to balanced fertility.  A healthy plant is more likely to tolerate the stress of winter and summer.  All plants and animals need balanced fertility (nutrition.)  This includes micronutrients as well.  Constant removal of nutrients resulting from harvest of crop and pasture has left some soils very low in micronutrients (copper, zinc, manganese, boron, etc.)  Do not let the word “micro” deceive you.  You do not need much, but you do need enough.

Call your local Extension Agent for details on where to get a soil analysis run. If, for some reason, a soil test is not possible, a reasonable pre-plant fertilizer recommendation is: N = 30 - 40 lbs.; P2O5 = 70 lbs.; and K2O = 50 lbs. of unit/lbs of N, P, K (nitrogen, phosphorus, and potassium, respectively) per acre.

 

Dennis Hancock, PhD, Univ of GA  wrote the followiing excellent article on fertilizer strategies, a must read for all:

 

Fertilization strategies for hay production
October 2009 – Progressive Forage Grower
Dennis Hancock, Forage Extension Specialist, University of Georgia

If you have been trying to get a grip on your hay costs, you likely have realized that one of the largest costs is tied to fertilization. Using current prices in the enterprise budgets put together by Dr. Curt Lacy, UGA Extension Livestock Economist, one can quickly find that fertilizer costs in the production of hay in our region are likely to be more than 40% of the total cost of production (Figure 1). I would dare say that the fertilizer costs for hay production in your region would be very similar.

Figure 1. The approximate breakdown of major costs associated with hay production in the Southeast.
At these prices, it is entirely logical to look for ways to reduce fertilizer costs. However, if the reduction in fertilizer costs results in reduced yield (i.e., less fertilizer often equals lower yields), then the cost of the forage per ton (or pound) can actually go up! The reason for this can be seen in the following equation that is used to calculate the unit cost of forage production:

 

Consider Table 1. Let’s assume in this example that the field we are dealing with has a yield potential of 6 tons of hybrid bermudagrass hay per acre. Based on current prices, the average cost of production for hybrid bermudagrass hayfields is approximately $750/acre (or $125/ton). If production costs are reduced and yields remain essentially the same, the unit cost
($/ton) decreases (green cells). However, it is likely that substantial reductions in costs in hay production will have to come from reductions in fertilizer expenditures (because fertilization constitutes such a big part of the total variable costs). Indiscriminant reductions in fertilizer will likely lead to reductions in yield. This may very well result in an increase in the unit cost ($/ton) of the hay (red cells). Thus, it is critical to remember that cutting costs in forage production should be done in a way that has a minimal impact on the forage yield.

 

Table 1. The unit cost of hay produced under different levels of cost (relative to the current average for hybrid bermudagrass hay) at different levels of hay production.

Management Tips

So, how does one reduce forage production expenses without compromising yield? The following tips can help reduce fertilizer expenses or at least make the investment in fertilizer more efficient.

 

Soil Test and Follow Fertility Recommendations. If one does not soil sample and apply fertilizer and/or lime based on the results of those tests, it is likely that they are either 1) not putting on enough fertilizer/lime and therefore the forage yield is below its potential, or 2) putting on more fertilizer than is required to meet the yield goals and therefore they may be wasting money. Few other practices in the hay production enterprise can improve the profitability more than soil testing and following fertility recommendations from your state’s Land Grant University.

 

Do NOT neglect your soil’s pH. Keeping an optimum soil pH will ensure that soil tilth is maintained, root development is encouraged, and (most importantly) the nutrients in the soil are freely available to the plants. If the soil pH drifts much below 6.0 or much above 7.0, the availability of some nutrients in the soil will decrease and some other nutrients can reach toxic levels (Figure 2). This can translate to a major waste of one’s “fertilizer dollar.” For example, a pH difference of 5.6 vs. 6.2 can effectively reduce the value of the N fertilizer by as much as 35%, the P fertilizer by as much as 50%, and the K fertilizer by as much as 10%. When totaled, this may mean that one has lost $40-75 worth of the fertilizer’s value in just one season because the soil pH prevented adequate nutrient availability.  Of course, soil amendments that rectify soil pH problems have benefits far beyond just one year and are very cost-effective on the short- and long-run.

• Focus Your Resources. Apply fertilizer to hayfields where soil test P and K values indicate an economic response to the addition of the fertilizer AND the soil pH is in the optimum range. If the soil pH is too high or too low, attempts to add P and K will result in a lack of return on the fertilizer investment. Instead, focus first on rectifying the soil pH problem in those fields. If possible, identify other fields or pastures that could be used as hayfields while the pH in that field is being corrected.
• Avoid the Use of Standardized Blends. Standardized blends (e.g., 10-10-10, 17-17-17, etc.) of homogenized (uniform particle size) fertilizer products are commonly sold. Unfortunately, these blends are usually much more expensive than custom mixed fertilizer products, which can be been tailored to meet the needs of the individual field or site’s target fertilization rate (Table 2). Using current prices, one can save over $100/acre by fertilizing a bermudagrass hayfield with a custom mixed fertilizer rather than a standardized blend.
• Use Animal Manures When Available, but be Strategic. Continuing the scenario that is posited in Table 2, note that the use of animal waste (and, in this case, supplementing to provide enough K) can reduce fertilizer costs by nearly 50%. Certainly, animal manure can be a cost-effective and beneficial fertilizer source. After many years of animal manure applications, however, nutrients can accumulate to very high levels in these soils. If this is the case, a producer may be better off applying commercial N and utilizing the P and K that has built up in the “soil bank.” Note from Table 2 that if soil test P and K levels are sufficient and only N is needed, then the total cost of fertilization would be much lower (i.e., the cost of urea fertilizer, in this instance).
• 
• Split Your Nitrogen Applications. Fertilizer recommendations are given as totals for the season. For some nutrients, the entire amount can be applied at one time with little economic or environmental risk. However, high rates of N application at the beginning of the growing season can result in unnecessary risk. This can be especially risky when conditions for leaching, volatilization, late frosts, or drought occur. Split applications of N also reduce the risk of nitrate toxicity. Further, long-term research has shown that yields can be increased by 5-10% and N use efficiency can be as much as 25-30% higher when N fertilizer applications are evenly split among 2-4 applications (or more, if your growing season allows) during the season.
• Apply Phosphorus when it is Convenient. Since P applied to the soil is relatively stable and generally available to the plant as it is needed, P fertilizer can be applied to the hayfield virtually any time during the year. This flexibility in application timing allows the producer to purchase P fertilizer in “off-peak” times of the year (i.e., summer and fall) when demand for the product and spreading services are lower. A major exception to this flexibility is that the recommended P rate should always be applied before planting annual crops or new plantings of perennial forages. Further, producers should avoid spreading P fertilizer when the risk of runoff is high. The loss of P in runoff is the primary way in which P is lost from soils and ends up lowering water quality. Some producers mistakenly believe that by using commercial P sources that they need not worry about runoff. This is not true. Runoff can be a problem regardless of the source of P being used. Recent studies have shown that losses from commercial fertilizers can actually be much larger than losses from animal wastes, when they were applied at similar rates.
• Split Your Potassium Applications. In contrast to N and P, the environmental risk posed by K is very low. However, K has become much more expensive than in the past, occasionally being more expensive than N. Therefore, care must be taken to ensure it is used efficiently. The biggest potential for inefficient use of K is a phenomenon called “luxury consumption.” Most plants (especially forage crops) will take up more K than is required for optimum growth, if it is readily available in the soil. Thus, if relatively large rates of K are applied early in the growing season, forage crops will absorb excess K and reduce the amount available for later growth cycles. Because of this potential for luxury consumption, it is recommended that K applications be split across two or more application times (50:50 or 40:60 splits, are common). This will lower the risk of luxury consumption and leaching, allowing K to be used more efficiently and available throughout the growing season.

 

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