Got Math? Numbers on a Dairy Farm

Thank You Post

2008-04-13T15:07:00.000-07:00

I want to thank my friends the Conants at Riverside Farm in Richmond for letting me come to the farm and gather information for my math notebook. Since moving to Vermont I have always been curious about the in's and out's of their farm and I am so glad that I finally found a way indulge my curiosities.

I also need to give a HUGE thank you to my husband Tom for taking several hours out of his Sunday to explain all of the different math that is included in his job as a crop advisor. He was very patient and quite a natural at teaching!

Nutrient Management Planning

2008-04-13T14:54:00.000-07:00

In today's environmentally conscious society farms are held to a high standard of environmental stewardship. Most states require dairy farms to meet these standards by following nutrient management plans. Nutrient management plans take into account all nutrient inputs (commercial fertilizer and grain) and outputs (manure, waste feed and animal mortality). The nutrient management plans purpose is to calculate and determine the amount of waste produced on the farm and then show that the farm has the land base to allocate those waste in an environmentally sound manner. The overall goal of the nutrient management plan is to limit the effect the farm has on the environment.

Soil Texture

2008-04-13T14:46:00.000-07:00

There are many different types of soils across a single farm. Different soils have different characteristics that play a role in everyday decision making in terms of crop production. Most farms know what soil types they have in each field, but if they don't know the soil type they can determine it by taking a sample, putting it in a jar of water, shaking vigorously to mix up then estimating the percentage of each soil type as it settles to the bottom in layers. Using the soil texture triangle below the farmer can determine what type of soil they are working with.

Pest Management

2008-04-13T14:38:00.000-07:00

A pest on a farm can be identified as weeds, insects, birds, bears, or anything that can negatively impact the crop. Farmers use economic thresholds to determine pest management strategies. If the pest is at a point where pest management costs equal a loss in income due to the damage from the pest they are at economic injury level. If pests are above economic injury level then it makes economic sense to invest in pest management. If pests are below economic injury level the farm will get no return on the pest management.

Pumpkins for Sale

2008-04-13T14:34:00.000-07:00

In the fall at Riverside Farm they sell pumpkins and squash. Like sweet corn they have to base their prices around the cost of production. The pumpkins and squash are sold by the pound. They use a large scale to weigh the produce and determine the price of each item.

Sweet Corn Sales

2008-04-13T14:26:00.000-07:00

In addition to growing corn for feed at Riverside Farm they also grow sweet corn to sell. Sweet corn is sold by the dozen/half dozen or per ear. The farm has to sell sweet corn at prices that are high enough to cover their costs of planting, growing and harvesting. During the 2007 season the prices were: $5.00/baker's dozen, $2.50/half dozen and $.35/ear.

Payroll

2008-04-13T14:22:00.000-07:00

A farm is like any other business, they must keep track of employees hours and pay them accordingly. The farm's book keeper keeps track of the hours that are worked, writes the paychecks and balances the farm's checkbook every week.

Units of Measurement in the Field

2008-04-13T14:16:00.000-07:00

Here are some examples of some of the important units of measurement that are used in farming:

1 acre = 43,560 sq. ft.
1 hectare= 2.471 acres
1 ton = 2000 lbs.
1 gallon of milk= approx. 9 lbs. of milk

Determining Corn Prices

2008-04-13T14:14:00.000-07:00

Values of corn are measured in bushels. Farms usually keep track of their yields in tons. Below is the conversion method between the two types of measurement.

A dry bushel of corn weighs 56 pounds. Therefore a ton of Corn will be just over 35.7 bushels. (2000 pounds/56 pounds= 35.714286)

Determing Yields

2008-04-13T14:05:00.000-07:00

To determine crop yields the farmer will weigh at least one load coming out of the field, then keep track of how many loads that are harvested from that field.

Example: one load= 20 tons

# of loads= 45 loads

field size= 42 acres

yield tons/acre = ?

20 tons x 45 loads= 900 tons

900 tons/42 acres = 21.43 tons/acre

Corn Silage Harvest

2008-04-13T13:53:00.000-07:00

When the corn plant has reached maturity it is getting close to harvest time. The farm's goal is to harvest the corn silage when it is at a certain percent dry matter that will maximize the transfer of energy from the silage to the cow resulting in a higher production of milk per cow.

This percentage of dry matter is approximately 32%. To check the percent dry matter of the crop while it is still in the field, farmers cut a few plants by hand and run them through a chipper to mimic the corn chopper. Once they have a chopped up sample of silage they can determine the percent of dry matter by weighing the sample when wet, cooking the sample to remove all moisture, and weigh again. (See picture of Koster tester above)

Ex. If the sample weighs 16 oz. wet and 11oz. after it has been cooked and dried it has a dry matter percentage of 32%. This tells the farmer that the crop is ready to harvest.

Determining Approximate Corn Harvest Dates

2008-04-13T13:33:00.000-07:00

Corn seed is genetically developed to grow better in different regions of the world. The longer the plants can stay in the field growing, the higher the yields will be. Corn grown in southern climates can stay in the fields longer than corn that is grown in the northeast. The length of time it takes for a corn plant to reach maturity is called relative maturity (RM). Relative maturity is measured in days.

To choose a corn variety that will produce the greatest yield, you want to choose one with an RM that matches the length of growing season in your region.

Ex. If the RM of the corn variety that you've planted is 95 and you planted on May 15th, when will your estimated harvest day be?

Answer: August 18th

Determining Plant Populations

2008-04-13T13:18:00.000-07:00

When farmers plant corn they are trying to maximize yield by planting the right amount of plants per acre. If there are too many plants they will compete with each other, if there are too few then they will not be able to protect themselves from the elements.

A typical plant population goal is 32,000 plants/acre. To check and make sure the corn planter is dropping the correct amount of seed to meet these goals the farmer will perform the following mathematical algorithm:

plants/acre= (plants/ft.) x (43,560 sq ft/acre) / (row spacing [in]/12 in/ft.)

Soil Sampling

2008-04-13T13:10:00.000-07:00

Farms take soil samples to determine nutrient levels in their fields. It is recommended to take a sample from every field. Larger fields require one sample per 20 acres, and are usually collected based on topography within the field.

Ex. You have a field that is 86 acres. How many soil samples will be needed from that field?

86/20= 4-5 samples depending on the topography/layout of the field.

Nitrogen Availability

2008-04-13T12:54:00.000-07:00

Nitrogen is one of the hardest nutrients for a farm to account for. Nitrogen in most forms is very volatile and sensitive to environmental/climate changes. The nitrogen in manure is in the form of ammonia and will volatilize if not incorporated into the soil. Most farms try to avoid this loss of nitrogen by incorporating the manure into the soil by plowing. Even if they plow the manure in the same day it was spread, only 80% of the nitrogen will be available to that year's crop.

The other form of nitrogen in manure is organic nitrogen. Organic nitrogen needs to be broken down by microbial life within the soil to become available to that year's crop. Approximately 35% of organic nitrogen is available in the first year.

Manure sample analysis measures both ammonia nitrogen and organic nitrogen. With this a farmer can determine how much nitrogen they are supplying the crop with the manure applications.

Nutrient Budget for Corn Silage

2008-04-13T12:27:00.000-07:00

Throughout the spring the farm keeps track of how much manure and fertilizer they apply to their fields. They use a nutrient budget to figure out where they are deficient or where they have over applied. Based on nutrient needs for corn silage a typical nutrient budget may look like the one below.

Nitrogen (lbs/acre) Phosphorus (lbs./acre) Potassium (lbs/acre)
Corn Silage Needs: 150 80 120
Manure Application 45 60 75
Fertilizer Application 30 20 10
Deficit/Surplus - 75 0 - 35

Nutrient Needs of Corn Silage

2008-04-13T12:18:00.000-07:00

The goal of fertilizing any crop is to maximize yield while minimizing cost. Therefore, the farm attempts to supply the crop with the necessary amount of each nutrient. Crops have a yield potential that is limited. Therefore, over applying nutrients is both unnecessary and costly.

Nutrient needs of corn silage:

Nitrogen = 150 lbs./acre
Phosphorus= 80 lbs./acre
Potassium = 120 lbs./ acre

Fertilizer Ratios N-P-K

2008-04-13T12:00:00.000-07:00

The farm can't supply all of the nutrients that are needed for their crops with just manure. They use commercial fertilizer to provide the remaining nutrients needed. Fertilizer values come in the form of a ratio. Each number in the ratio is a percentage of that nutrient, based on the total weight of the fertilizer mix. The three major nutrients in all fertilizers are Nitrogen, Phosphorus and Potassium. A typical fertilizer mix that is commonly used has a ratio of 7-22-5.

In order to figure out how many pounds of each nutrient are in this fertilizer you would do the following math.

Ex. N-P-K 7-22-5

Total Mix= 2000 lbs.

Total N = 140 lbs.

Total P = 440 lbs.

Total K = 100 lbs.

Manure Nutrient Value

2008-04-13T11:51:00.000-07:00

The farm uses the manure produced as fertilizer for its crops. To figure out the nutrient value of the manure they collect a sample and have it analyzed in a lab. Here is an example of a manure sample analysis. With this data the farm can see how much of each nutrient they are supplying the crop with each manure application.

Manure Spreading

2008-04-13T11:39:00.000-07:00

The first field work to be done in the spring is to start spreading the manure that has been collecting in the manure pits through the winter.

Because the manure contains many valuable nutrients the farm wants to make sure they are applying manure at effective rates, while not over applying and running the risk of run-off and pollution of surface waters. Most farms work with a nutrient management planner to help them come up with both effective and environmentally sound spreading rates. These rates are usually given in 1000 gallons/acre recommendations.

Ex. Recommendation - 6,000 gallons/acre

Field Size - 10 acres

Total Manure Spread - 60,000 gallons

Crop Needs

2008-04-13T11:24:00.000-07:00

Most farm's animal numbers grow every year. Because of this increase the farm has to determine how many acres of crops they will need to feed their herd in the upcoming year. They do this with the help of the nutritionist by looking at the ration needs per cow and multiplying that number by the number in the total herd.

In this region farms usually average 16 tons of corn per acre. Once the farmer knows how much corn he will need to feed his herd for the year he can figure out how many acres of land he will need to use for corn.

Price of Milk

2008-04-13T11:11:00.000-07:00

The farm is paid for the milk that they produce by using hundred weight (CWT). For every 100 lbs. of milk they send off the farm they currently receive about $ 20.00. The CWT will fluctuate based on many different factors (ex. economy, gas prices, seasonal weather). The farm tries to prepare for fluctuations by looking at past trends and future predictions.

Feed to Milk Ratio

2008-04-13T10:57:00.000-07:00

In order to figure out how much milk the cow should be producing, the farmer uses the feed to milk ratio. The ratio is 2.3 : 1. The first step is to determine how much dry matter (nutrients supplying energy to produce milk) is in the ration. At Riverside Farm their current ration is 122 lbs./cow of which 55.65 lbs. is dry matter.

2.3 x 55.65 = 127.995 pounds of milk per day/cow

Figuring Rations

2008-04-13T10:43:00.000-07:00

Every morning the farm has to mix the feed wagon with the correct rations based on recommendations from their nutritionist. The ration is made up of a combination of corn silage, hay silage, cotton seed and grain. At Riverside Farm the nutritionist currently recommends a ration/ milking cow of 70 lbs. corn, 25 lbs. Hay Silage, 4 lbs. Cottonseed and 23lbs. grain.
Riverside Farm milks approximately 400 cows.

Calf Feeder Planning

2008-04-10T17:43:00.001-07:00

The farm milks their cows twice per day. During milking they set aside enough milk to feed their calves. Now the feeder needs to figure out how much formula they need to mix with the set aside milk to feed calves for a week. Once they know what they need, based on how many calves there are that week, they call the Dairy Supply rep and order what they need.

ex. 15oz. of formula per day x 2 feedings= 30 oz. per day for each calf

30 oz. per day x 3 week old calves= 90 oz. per day

90 oz. per day x 7 seven days= 630 oz. of formula per week

Feeding Calves

2008-04-10T17:15:00.000-07:00

A week old calf needs 3 quarts of milk mixed with 15 ounces of formula twice a day. Whoever has this chore for the day has to figure out how much to mix based on how many week old calves they have that day.

At Riverside Farm they have an average of 3 week old calves at a time.

3calves x 3 quarts of milk = 9oz. x 2 times per day= 18 oz. of milk

3 calves x 15 oz. of formula= 45 oz. x 2 times per day= 90 oz. of formula