Friday, January 30, 2015

Land Use and Manure

We all know that our land resource base is finite. No matter what, Iowa is only going to have an area of 55,857 square miles (or just under 36 million acres); of this, about 26.2 million acres, or about 73% of the state, is farmland. How we choose to use this land can have profound impacts on our ability to produce food, fuel, and fiber and the impacts we have on the environment. Our goal here is not to discuss the different impacts choosing alternative land uses can have, but rather to look at how we are currently using our land, especially farmland use, and how it varies throughout the state.


As we do this we are going to focus on two maps of Iowa, the first gives the percent of land in each county in Iowa that is classified as farmland. As stated above, as a state, Iowa has 73% of its land in crop production, but this changes pretty substantially throughout Iowa with a low of 34% in Appanoose to a high of 94% in Palo Alto and Grundy counties. This map is shown below, each county is color coded with darker green counties having a lower percentage of its land in cropland, and more red counties having a higher percent of its land in cropland. What we see should be pretty expected, both the Des Moines lobe soil formation and the loess soils of western Iowa. Much lower percentages of our land are used for cropland in southern Iowa, especially south central and southeast Iowa.
Figure 1. Percent of land that is cropland (based on 2012 Census of Ag).

As a follow-up I was also interested in what percent of our cropland we are using for corn production. As a state Iowa averaged 54% of its cropland planted to corn, but again this varies throughout the state. In this case the lowest value was 25% corn, which occurred in both Lucas and Appanoose counties, while the high was 73% which occurred in Delaware county. In this case the pattern indicates that the northern 2/3 of the state have more corn in their rotations, as these counties typically had more than 50% of their cropland planted to corn, while the southern 1/3 of the state utilized different crops, as they often had less than half their cropland planted to corn.
Figure 2. Percent of cropland that is planted to corn (based on 2012 Census of Ag).

So, what does this have to do with manure? Well, growing corn requires a fair bit of nutrient, both nitrogen and phosphorus, so it is often an excellent crop to utilize our manure resources to grow. In fact, I have read several pieces of scientific literature that state we find more continuous corn rotations around swine farms, potentially this could be try if we were trying to find crops to use our manure nutrients on a few of acres as possible to limit the distance we have to haul the manure. Alternatively, it might be true if our manure was proving serving as a super-cost effective fertilizer that its use as or fertilizer source made continuous corn rotations more profitable than the corn-soybean rotations. (I have looked at this question a bit, and will soon share with how estimated profits for continuous corn and corn-soybean rotations compare if you are using manure as the fertilizer or if you are using synthetic nitrogen fertilizer and what I think this means for rotation selection).

So that got me wondering, is animal farming (or manure production) driving our crop selection patters at the landscape level? That is, are our animal farms in Iowa driving a land use change where we see more of our land being used for corn production, which would be indicative of continuous corn rotations). This could be an important question, as Iowa State research has generally showed greater nitrate leaching potential in continuous corn rotations than in corn-soybean rotations, probably due to the greater fertilization requirements in continuous corn situations as compared to corn-soybean rotations. What I found indicated that there was no relationship between manure production and the choice to plant more corn (at least at the county level and across all animal species). This is shown below in figure 3, what the data shows is random scatter around a flat line describing the relationship between how much manure nitrogen is available in a county and the amount of that county’s cropland planted to corn. When I focused just on swine farming, I saw a very similar pattern, i.e., no relationship between animal production and the percent of crop ground planted to corn. This technique provides pretty good evidence that at the county level, animal farming doesn’t seem to be driving our crop rotation choices.
Figure 3. Relationship, or lack thereof in this case, between the amount of manure produced in a county and the percent of cropland planted to corn within a county.

So… what does this all mean, and why was I doing it anyway? Well, next time you hear someone say animal farming is causing us to grow too much corn, you can say that having animals in your county doesn’t appear to increase how much corn is grown.

The reason I started this analysis was far different than what I’ve shown today. I was interested in determining when a nutrient partition (nutrient separation) manure treatment technology would be cost feasible to implement. To do this I was evaluating how a farm’s costs of manure application changed with differing levels of treatment effectiveness. Performing this analysis requires information on how the manure will be distributed, i.e., the transport distance from the farm. This is dependent on the availability of land for manure application and the amount of manure (in terms of total nutrient need) that can be applied. These values most certainly vary from farm-to-farm as they depend not only on items including topography, road placement, locations of streams and drainages, and variables of the like, but also on how much land the farmer owns, the willingness of neighbors to either accept or buy manure nutrients, the crop rotations being utilized, and the yield potential of the crop. Hence an interest in understanding how much cropland and in particular corn ground is available for manure application as this will impact our result, so yet again, something for you to look forward to in the future.

Thursday, January 22, 2015

Manure Agitation - What is a manure agitation boat?

A well-designed manure storage facility must also be well managed to prevent environmental concerns from developing. This includes things like making sure that structural components remain in good repair, keeping the landscaping around the facility mowed, clean, and cutting down trees and brush growing right next to the storage so that the storage can be easily inspected for concerns or connection failures. Although these things are important, the most important requirement is still making sure to get it emptied so that enough capacity is available to make it to the next land application window.

Achieving good agitation is an important part of this. Failure to properly agitate the manure will result in a continuous buildup of settled solids within the storage, resulting in less and less available storage as time goes by. Good agitation of the manure will re-suspend those settled solids and facilitate their removal from the storage ensuring we maintain that capacity we need. Additionally, agitation of the manure helps homogenize it and provide a more consistent nutrient content as it is applied. Below I’ve provided a conceptualization of what we typically think of as our solids profile in manure storage, what we think happens is we get an accumulation of course solids where the manure enters the storage and a sludge, of partially degraded organic matter,  over the whole storage. The way this develops can be impacted by the amount of water added to the manure, the type of bedding material used, the agitation history of the storage.



Many types of agitators are available for agitating slurry systems, including hydraulically or mechanically driven propellers or choppers, bypass devices on manure loading pumps, and manure agitation boats. Your choice of manure agitation equipment should be based on the level of agitation needed, the design and configuration of the slurry manure storage facility (where you can place agitators and how many), and the volume of manure to be agitated. Pictures of these different types of agitators are provided below. Of these, you are probably familiar with the first two, but agitation boats are relatively newer. The big difference being that our traditional agitators are constrained to somewhere near the edge of the storage, while boats can move throughout the storage potentially getting better agitation in areas we couldn’t reach before.



 


So, what is a manure agitation boat? It is basically a remote controlled floating pump system with a series of nozzles. This lets the user direct it throughout the manure storage, direct the fow of manure, and steer it around to better mix the manure. I recently had the chance to chat Jamie Tews about his agitation boat to get his perspective with an using agitation boats and what some of their benefits. To take a listen to this interview click the link below (you’ll go to our YouTube channel as the video was just too big).


Whats and Why's of Manure Agitation Boats


Hopefully in the future we’ll get a chance to talk in more detail about how these things work, what the might mean for our manure storage design and management, and some tips for operating them to maximize performance.

Tuesday, January 13, 2015

What is water conservation worth? Swine edition

As we strive for sustainability, water conservation is an important industry, with agriculture and animal production being no expectation. Besides being environmentally responsible, reducing the amount of water wasted in a barn has several positive benefits. First, and most importantly, every gallon that ends up in the manure has to be land applied, and depending on your application rate and distance to cropland this can cost upwards of $0.01-0.02 per gallon with an additional charge of around $0.001 per gallon per mile hauled beyond the first mile. Reducing water wastage also reduces the required manure storage capacity and expenses related to pumping and purchasing water.

Water is used for three main purposes in swine production: animal drinking, animal cooling, and facility/equipment washing. It is estimated that at a swine finishing site, the average whole farm consumption of water will be around 1.5 gallons per pig per day. Of this about 7% of the water is from facility washing, 12% from animal cooling, and 80% from animal drinking, with the remaining 1% from domestic uses which includes drinking, hand/boot washing, laundry, and showering. To put this into perspective, it is estimated that the average American uses 80-100 gallons of water per day in their home!

As animal water consumption accounts for the greater amount of water use, a large emphasis has been placed on the impact different drinkers have on water use. Examples of different drinkers include nipple drinker, cup drinkers, and wet/dry feeders. In each case there are many styles of each of these drinker types, but for classification purposes I’m calling: (1) a nipple drinker any drinking device that allows water not consumed by the pig during drinking to flow directly into the manure storage; (2) cup drinkers any animal drinking system that provides a cup or bowl for pigs to drink from and are filled by a pig actuated lever or nipple or a water level activated float level; and (3) wet/dry feeders to be a feeding/drinking system that mixes the dry feed and water into the same bowl, tray, or trough. Example of each of these types are shown in the pictures below.


A solid mounted nipple drinker and close-up of the nipple drinker.


A nipple square bowl with standard mouthpiece and a shallow cup drinker.


A shelf style wet/dry feeder and wet/dry feeder.


Research has tended to indicate that as you switch from dry feeders and nipple drinkers to dry feeders and cup drinkers or wet-dry feeders, water consumption decreases. This intuitively makes some sense as by design, cup/bowl drinkers should decrease water wastage as water related from the lever falls into the cup for the pig to drink. Similarly, wet/dry feeders are designed to catch any water from the nipple and offer the ability for it to mix with the feed.
Building Type
Whole site
water usage
(gal/pig space-day)
Animal Drinking Consumption
(gal/pig space-day)
Other water
(gal/pigs pace-day)
Finisher, dry feed/nipple
2.33 (0.32)
1.87
0.46
Finisher, dry feed/cup
1.15 (0.17)
1.00
0.15
Finisher, wet/dry
1.25 (0.33)
1.19
0.06

Water is used to wash swine facilities before a new group of pigs is placed. In general little literature is available on water consumption during barn washing. However, a study by Hurnik (2005) did compare several different techniques including hot and cold water, soap usage, and pre-soaking the facility. They found that using hot water reduced washing time by about 22%, using soap reduced washing time by 8%, and pre-soaking could reduce washing time by up to 50%. Unfortunately, no water consumption values or pre-soak times were reported for the different treatment. However, an industry survey indicated that on average about 3 gallons per pig space per wash were used in power washing the barn. General practice is to pre-soaking the facility before washing and this appears to increase water consumption to about 7 gallons per pig space to wash.


So let’s see if we can put some numbers on this, if you were to switch from a nipple drinker to a cup drinker. Assuming that pigs are still getting all the water they need, since it is offered ad lib, then any difference in water consumption is directly proportional to the amount of slurry being produced. In this case, the change would result in a reduction 0.87 gallons per pig space per day (1.87 gal/pig space-day – 1.00 gal/pig space-day), or about 300 gallons per pig space, per year. Which would result in a saving of about $4.50 per pig space per year in manure application costs. In addition to the reduction in cost from manure application, if you are using rural water  there is also a cost of getting your water (Polk County Rural Water District #1 is charging $4.00/1,000 gallons). This means saving 300 gallons would reduce costs by about $1.20 per pig space per year, for a total savings of $5.70 per pig space per year. This compared to an estimated cost of about $2.50-4.50 per pig space to switch to cup or bowl drinkers.


Wednesday, January 7, 2015

Iowa Manure Management Plans: Yield Goal Method versus the Maximum Return to Nitrogen

A manure management plan is a tool for animal farmers that describes how they plan to place and use their manure nutrients for crop production. The process of filing out a manure management plan makes producers identify the amount of manure they expect their farm to produce, estimate the nutrient concentration in the manure, determine the number of acres that are required for land application, and then detail the amount of manure that will be applied to each available acre. In Iowa these plans are based both on the nitrogen needs of the crop as well as the phosphorus index for each field.

Current Iowa law states, “Nitrogen-based application rates shall be based on the optimum crop yields and crop nitrogen usage rate factor values or from other credible sources. Nitrogen-based manure rates shall account for legume production in the year prior to growing corn or other grass. Therefore, I’m going to take a minute to compare these options to try to better understand what they mean for manure nutrient management. The first approach to calculating the nitrogen application rate desired to support crop production is the yield goal method. In this approach, the farmer determines the optimum yield of the crop and then multiplies the yield times a crop nitrogen usage rate factor for the specific crop. The required nitrogen rate is then adjusted for ammonia losses during application, the nitrogen availability of the manure, and any previous legume crops grown in the field. The optimum yield for each crop may be set to either the average of the last 5-year county yields plus 10 percent or the average of the highest 4 out of the last 5-year county average.

The other approach is the maximum return to nitrogen. This approach uses economic return to N application found in research trials as the basis for the suggested N rate. The average of N responses accumulated from a population of N rate trial sites is used to estimate the point where net return is the greatest (an example of yield response curves shown below). That is, it identifies the nitrogen the point where the next added unit of fertilizer results in a yield increase that based on the value of corn is equal to the price of that unit of nitrogen. This may sound complicated, but a tool to help with these calculations is available at: http://extension.agron.iastate.edu/soilfertility/nrate.aspx. Input a corn price, a nitrogen fertilizer price, select your crop rotation (corn-soybean or continuous corn), and select which state or fertilizer region you are in, and the program generates an estimate of what fertilizer rate will give you your maximum return to nitrogen.



So now we get to the important part, how do these two methods compare.
To determine the maximum return to nitrogen we have to estimate a nitrogen price (I used $0.44 per pound) and a corn price (I used $3.75 per bushel) for both a continuous corn rotation and a corn soybean rotation (fertilizer recommendation for the corn phase). The results indicated that my maximum return to nitrogen would occur at a nitrogen application rate of 132 (120-145) lbs N/acre in the corn-soybean rotation and at 184 (172-197) lbs N/acre in the continuous corn rotation (numbers in parenthesis produce a profit estimated to be within $1 per acre of the maximum return to nitrogen). I then compared this to the amount of nitrogen that would be applied if the yield goal method was used (the ideal yield was set to the higher of the average of the last 5-year county yields plus 10 percent or the average of the highest 4 out of the last 5-year county average). The manure application you’d pick based on yield goals is summarized in the table below (end of the post).

When I compared the  results of the maximum return to nitrogen and yield goal approaches for nitrogen application rates, I found that in 82 of Iowa’s 99 counties the maximum return to nitrogen resulted in a lower nitrogen application rate than the yield goal method in a corn soybean rotation. In these cases the yield goal method resulted in a nitrogen application rate within $1 of the profit produced at the maximum return to nitrogen in 18 of the counties, a lower nitrogen application rate in 11 of the counties, and a higher application rate in 70 of the counties as compared to the maximum return to nitrogen approach. Similarly, in the continuous corn rotation the results showed that 15 counties produced application within the $1 max profit nitrogen application bracket, a lower nitrogen application rate in 15 of the counties, and a higher application rate in 69 of the counties as compared to the maximum return to nitrogen approach. These comparisons are summarized in the figure of Iowa shown. In the counties left white, the maximum return to nitrogen recommended nitrogen application rate was less than that calculated for the yield goal approach for both continuous corn (CC) and corn soybean (CS) rotations. In the green-shaded counties, the yield goal method predicted a nitrogen application rate within the range provided by the maximum return to nitrogen concept for either the CC, CS, or both, depending on the shade of green as specified in the figure. Finally, in the counties shaded orange or red the maximum return to nitrogen approach suggested a higher nitrogen application rate than what would be estimated based on the yield goal approach.
  

So which method should you use? I think both methods have some strengths and limitations. Conceptually the yield goal method seems really nice as it’s essentially a mass balance approach where we try to supply the amount of nitrogen we will be removing with the harvested portion of the plant as well as what we might be losing to other places. However, in practice, its accuracy is limited by our ability to accurately estimate increased nitrogen cycling resulting from a rotation effect with a legume (especially soybean in the corn-soybean rotation) and in general it doesn’t predict the application rate that will maximize our profit in using nitrogen. On the other hand, in the maximum return to nitrogen approach we have a much better chance of applying at the rate that maximizes the nitrogen value of the manure. However, in addition to just nitrogen, manure also supplies other nutrients like phosphorus, potassium, and organic matter which may impact how we value this nutrient source. Additionally, in some high yield cases, the maximum return to nitrogen approach may recommend nitrogen application rates below what is being removed with the harvested corn grain (about 175 bu/acre in a corn soybean rotation and 232 bu/acre in a continuous corn rotation).

So that’s a fair amount of discussion with no solid answer about which method to use. I think that the maximum return to nitrogen concept is preferable as it attempts to make better use of our nitrogen resources. However, if your fields yields are consistently larger than the 175 bu/acre in a corn-soybean rotation and 232 bu/acre in a continuous corn rotation, I’d probably switch to using the yield goal method. In general, I’d prefer to write my manure management plan with using the yield goal method, but when it comes time to apply my manure, I’d collect my manure sample, determine its nitrogen content, and adjust my application rate to try to achieve an application within the range the maximum return to nitrogen approach suggests.

Additional resources for selecting your nitrogen application rate can be found at:
PM-1714 “Nitrogen Fertilizer Recommendations for Corn in Iowa” available at: https://store.extension.iastate.edu/Product/Nitrogen-Fertilizer-Recommendations-for-Corn-in-Iowa
PM-2015 “Concepts and rationale for regional nitrogen rate guidelines for corn” available at: https://store.extension.iastate.edu/Product/Concepts-and-Rationale-for-Regional-Nitrogen-Rate-Guidelines-for-Corn





Corn-Soybean
Continuous Corn
County

Corn
(bu/acre)
Soybean
(bu/acre)
N use factor
(lb N/bu)
Nitrogen Application
(lb N/acre)
Nitrogen Application
(lb N/acre)
Adair
157
47.2
1.2
141
188
Adams
158
47.2
1.2
142
190
Allamakee
186
51.4
1.2
173
223
Appanoose
115
39.4
1.2
99
138
Audubon
176
52.5
1.1
144
194
Benton
180
52.5
1.2
166
216
Black Hawk
181
50.4
1.2
167
217
Boone
183
48.8
1.2
171
220
Bremer
192
52.1
1.2
180
230
Buchanan
184
50.1
1.2
171
221
Buena Vista
189
49.3
1.2
178
227
Butler
188
51.5
1.2
176
226
Calhoun
174
46.2
1.2
163
209
Carroll
177
50.2
1.2
162
212
Cass
175
51
1.1
143
193
Cedar
194
56.3
1.2
183
233
Cerro Gordo
176
47.1
1.2
164
211
Cherokee
200
54.1
1.1
170
220
Chickasaw
185
49.5
1.2
173
222
Clarke
118
39.8
1.2
102
142
Clay
195
51.2
1.1
165
215
Clayton
192
56
1.2
180
230
Clinton
191
54.1
1.2
179
229
Crawford
189
52.1
1.1
158
208
Dallas
170
49.3
1.2
155
204
Davis
118
38.9
1.2
103
142
Decatur
124
41.3
1.2
108
149
Delaware
188
54.4
1.2
176
226
Des Moines
162
50.4
1.2
144
194
Dickinson
189
48.9
1.2
178
227
Dubuque
195
55.8
1.2
184
234
Emmet
193
49.3
1.2
182
232
Fayette
186
52.4
1.2
173
223
Floyd
182
49.8
1.2
169
218
Franklin
188
49.3
1.2
176
226
Fremont
174
48.7
1.1
143
191
Greene
177
47.6
1.2
165
212
Grundy
195
56.1
1.2
184
234
Guthrie
160
47.3
1.2
145
192
Hamilton
174
47.6
1.2
161
209
Hancock
187
49.1
1.2
175
224
Hardin
189
52
1.2
177
227
Harrison
184
48.4
1.1
154
202
Henry
150
49
1.2
131
180
Howard
186
48.9
1.2
174
223
Humboldt
183
48.6
1.2
171
220
Ida
201
53
1.1
171
221
Iowa
179
53.4
1.2
165
215
Jackson
175
52.6
1.2
160
210
Jasper
180
52.4
1.2
166
216
Jefferson
135
45.9
1.2
116
162
Johnson
180
50.6
1.2
166
216
Jones
185
54.1
1.2
172
222
Keokuk
155
49.6
1.2
136
186
Kossuth
196
50.4
1.2
185
235
Lee
140
45.3
1.2
123
168
Linn
184
51.8
1.2
171
221
Louisa
166
50.6
1.2
149
199
Lucas
116
39.8
1.2
99
139
Lyon
204
54.6
0.9
134
184
Madison
150
45.7
1.2
134
180
Mahaska
169
51.6
1.2
153
203
Marion
155
48.3
1.2
138
186
Marshall
187
56.1
1.2
174
224
Mills
178
50
1.1
146
196
Mitchell
186
48.2
1.2
175
223
Monona
180
49.7
1.1
148
198
Monroe
117
41.7
1.2
99
140
Montgomery
174
49.1
1.1
142
191
Muscatine
174
52.2
1.2
159
209
O'Brien
205
54.4
1.1
176
226
Osceola
203
51.2
1.1
173
223
Page
162
47.4
1.1
131
178
Palo Alto
193
49.4
1.2
182
232
Plymouth
187
53.7
1.1
156
206
Pocahontas
192
48.3
1.2
182
230
Polk
170
50.4
1.2
154
204
Pottawattamie
185
52.2
1.1
154
204
Poweshiek
182
54.4
1.2
168
218
Ringgold
119
42.4
1.2
100
143
Sac
183
49.7
1.1
152
201
Scott
179
55.9
1.2
165
215
Shelby
192
53
1.1
161
211
Sioux
201
56.8
1.1
171
221
Story
175
50.3
1.2
160
210
Tama
185
55
1.2
172
222
Taylor
141
42.3
1.2
127
169
Union
138
47.4
1.2
118
166
Van Buren
132
43.8
1.2
115
158
Wapello
138
44.1
1.2
122
166
Warren
142
47.2
1.2
123
170
Washington
166
51.6
1.2
149
199
Wayne
117
38.6
1.2
102
140
Webster
181
47.9
1.2
169
217
Winnebago
188
49
1.2
177
226
Winneshiek
192
50
1.2
180
230
Woodbury
181
48.9
1.1
150
199
Worth
185
47
1.2
175
222
Wright
186
48.2
1.2
175
223