Spring Soil Sampling

Soil sampling has traditionally been done in the fall, after crops are harvested. The objective is to know how much fertility the soil already has to produce next year’s crop. 

But in my business, more than half my sampling is done in the spring. We usually begin sampling when fields are planted or ready to plant and continue until crops are no more than 12-inchs tall to minimize damage to the crop. I have found ATV damage to be minimal at this stage. The photo below shows corn has recovered a day after sampling.

  

One of the reasons for spring sampling is that the soil moisture and temperature conditions are usually more consistent in the spring. Moisture and temperature when soils are sampled can affect soil test results. That is the reason that experts agree you should sample at the same time of year every time you sample. In fall, soils can be dry and/or cold. I have seen potassium results as much as 75 pounds per acre lower when sampled dry as opposed to sampling later after soil is moistened by rain. I have not been able to find any problems with sampling wet soils if you are not cutting ruts. 

Another advantage to sampling in spring is that results and recommendations can be ready before harvest to allow for earlier fertilizer purchase and more timely application. Application can follow the combine. With fall sampling, there is usually a delay between harvest and getting results. 

Frequency of sampling is also an issue in the fall. The Illinois Agronomy Handbook says that once in four years is enough. The problem is that variations in crop yields because of dry or wet conditions may be difficult to account for when sampling only once in four years. We sample every year or two to take the guesswork out. If you base your fertilizer application on removal rates, keep in mind that your crop does not read the removal charts and removal is often more or less than the charts say. 

No matter when you sample it is important to use proper techniques to assure consistent results. A soil probe and bucket are essential tools. Sample depth should be 7 inches in order to assure that your pounds per acre of nutrient is calculated correctly. 

I like to sample in management zones, but the zones can be difficult to define for some people. Using USDA SSURGO data can be a place to start, but I find that about half the time it does not suit my needs.  I like to use the five factors of soil formation to help me determine where the lines are between the zones. The factors include climate, organisms including vegetation, relief (or topography), parent material, and time. Yield maps can sometimes be used to determine zones. Some scientists like to use a Veris to measure electrical conductivity, which can define zones. I usually divide the field into major landforms and then subdivide to get 8- to 11-acre zones. I pull 10 to 15 cores over the zone to put less weight on old spread gaps and overlaps. Zones can be smaller if needed. 

If you grid sample, you should still make sure the grid point defines the part of the field sampled. Avoid waterways or anomalies. Also, to avoid the old spreading gaps and overlaps, be sure to go 10 to 15 feet from your ATV and maintain that distance as you walk in a circle pulling 8 to 10 cores. There is a good bit of research that supports the need to pull many cores. 

This illustration from Michael Dunn of Anez Consulting, LLC in Little Falls, Minnesota, shows how grid sampling can distort what is in the field.  It is used by permission. 

Samples should be air dried. It is OK to use a fan but avoid heat over 125 degrees Fahrenheit. 

Many people are considering switching corn acres to soybeans. One consideration is crop insurance.  Check with your agent for help sorting it out. You may have a soil consideration with saturated soils if you have applied nitrogen for corn. Denitrification can occur fast on saturated soils. If there is nitrogen left, you may want to plant corn. You should soil test to see how much nitrogen remains in the soil. Your pattern for nitrogen sampling should assure that some of the cores are from the knife track and some are from the in-between areas. I get good results sampling a foot deep, but the University of Illinois says to sample 2 feet deep. Samples need to be spread out and fanned so they dry in 24 hours. You can also use an in-field nitrate tester, but they will miss the ammonium form of nitrogen. If you know you are not wasting nitrogen applied, you may not feel bad about switching to soybeans. If herbicides have been applied, make sure they will not cause a problem either. 

The bottom line when growing soybeans is that you need to make sure that your fertility levels and fertilizer applied will support the high yields desired.

Interesting area today

I was surrounded by industrial and residential land where I was working today. As I headed to one fields, I noticed the sign about remote control locomotives.  As I was working, a short train went by.  There was a caboose in the forward position, and it was occupied.  The locomotive was in the middle and appeared to be empty.  The industry sort of isolated the area and served as a sanctuary for the deer who were not very wary of me at all. They are protected from hunting.

Remote Controlled Locomotive

Tame Whitetails?

Soil Sampling Strategies

I have written several times about why we use zone sampling to give our customers advice on nutrient management.  The biggest weakness of a grid sample is that it is tied to a spot and extrapolated.  Zones are tied to soil features, yields, topography and other pertinent information.
Sampling is across the whole zone.  The article in No-Till Farmer Talks about the two strategies and defines them very well.

When to Soil Sample

The short answer is, "When you can get a soil probe in the ground." There may be other things to consider, but if you are farming "new" land, that may be good enough.

We all know that good representative soil samples give us the opportunity to make fertilizer and liming decisions based on technical, scientifically obtained data.  How do we assure that data is valid enough that we do not short change ourselves on fertilizer and lime?

• Pull soil samples in the same season every year

We usually start in Mid-March and work until crops are too tall in Mid-June.  In fall we start as soon as complete fields are harvested and continue until Thanksgiving or shortly thereafter.  We try to do the same customers at the same time of year, year after year.  Our first customer in the spring is always our first customer in the spring.  Producers tend to have similar timing in operations year after year.  It is surprising that year after year, we tend to sample the same fields on nearly the same date.  (yes I track that) 

• Sample under similar conditions every year

This pretty much follows the seasonal reasoning.  Soil test results can vary depending on soil moisture and temperature, so we are likely to see results following a predictable pattern from year to year.

We are able to cover more acreage in the spring-summer sampling season than in the fall.  For the most part we can cover the land we want to cover better in the spring.  Individuals doing there own sampling can time sampling on their own.  In the fall, we are captives of the speed of harvest.

The graph below reflects some of the variation we see because of moisture and temperature from year to year.  It gives you a good idea of why we sample yearly.  If you do  not have frequently collected data, you never know where you might be as far as whether the soil test is higher or lower than it "should" be.

While sampling at the same time of year is important, if it has been several years since you have sampled, and you want to switch seasons, it may be a good time to switch.  Spring sampling has the added advantage that recommendations are available before harvest. 

Value of Soil Testing

No-Till Farmer recently shared a study out of Kansas State on the  Economic Reurn of  Soil Testing. With low prices, you may be looking for ways to cut back.  Soil testing and consulting may be one of those things you are considering.  The Kansas State Data suggest you actually get  better return on soil testing when crop prices are low.

Soil Sampling Advice.

No-Till Farmer gives advice out of Kansas State offering seven tips on soil sampling. The advice is not terrible.  It mentions using the factors of soil formation, but it really does not get into how.  The advice about lots of samples is good.  I have seen research results that indicates 15 cores per sample is the way to go.  Many grid samplers only get 3 to 5 probes per sample.  The also don't mention that the sample needs to be well mixed by grinding or crushing to get a representative sample.  Sometimes high clay soils are too wet to get them mixed well.  We dry those samples and crush or grind before they go to the lab.  The article also mentions seasonal variability.  The causes of variability that I have seen are moisture and temperature related.  Sampling conditions may not always be perfect, but data is better than no data when making your fertility decisions.  For precision farming, defining your sample areas is critical.   You also need the technological expertise to make variable rate maps. Maybe some of this information leads you to hire a consultant. 

Last Day of Spring Sampling

We wrapped up our spring sampling season today. It looks like just in time for the heat to set in.  I had to walk a corn field because it was too tall, but the soybeans I sampled were not too far along.  I did see some one who was still planting soybeans near Shipman.  The respite is temporary because we will have limited acreage of wheat ground to sample in a few weeks.  We will also be sampling a limited amount for soil health tests through the summer.  There are also field days and programs coming up..

Still Soil Sampling

I worked today soil sampling in the Freeburg area.  In some places the bare ground was frozen solid enough that I could not push the probe in by hand.  The good news is that my customer had not tilled anything.  I could kick away some residue and push in easily.  The question many  might have, is, "Is it too cold to sample."  We know that temperature, moisture, and other environmental factors can affect soil test values, but the experts also say that if you sample a certain field at the same time of year you will be able to be fairly certain that your test levels are valid.  I always sample this particular client when the weather is very cold.  The only thing different about today was a bit of snow flying at times.  It amazes me how often I sample a field on or near the same date every year. 

One Acre Grids - Real Accuracy or Perceived Accuracy

The latest issue of Prairie Farmer Contains  an Article about sampling with one acre grids. I see problems with this technique because it is still a grid sample.  Grid samples are by definition a spot sample.  The idea of a soil sample no matter technique is to represent a particular part of the landscape by sampling and testing a very small part of that landscape.  We then try to relate soil test results to the potential for the crop to respond to additions of fertility.  The hope is that we can maximize yield potential by increasing fertility to a level where the crop is not likely to be stressed by nutrient deficiency in that sample area.  By sampling on smaller grids we hope to have  more accurate picture of what is going on in a field.  In 1976 and 1977 Dr. Ted Peck was trying to teach me everything he knew about soil fertility and soil sampling.  He had a University owned field that had been sampled on a very intense grid in 1960.  256 samples had been pulled in that 40 acre field representing 0.15625 acre in each sample.  This was grid sampling at its most intense.  Results of Bray P1 testing are shown below.  You would think that by pulling samples so close together we would begin to pick up a pattern in the field, but it seemed that the closer together we got the more random the result in relation to other results.  This pattern held for the most part on pH, and Potassium tests as well.  The only place we saw a little bit of a pattern was in the calcareous soils.  Dr. Peck used these results to recommend that soil samples be pulled as close together as possible.  Thus we went from puling 11 samples in a 40 acre field to pulling 16 samples and the 2.5 acre grid was born. 

My opinion is that the results below make a good case for trying to map areas with similar soil properties and then pull samples from the whole management zone.  Our zones average about 10 acres in size, but they can be much smaller if needed to properly characterize a problem area or potential problem area.  We also use yield maps or yield potential to confirm the zones that we define by making our own maps that define soil type by landscape units and drainage class as well as topography.  We sample across the whole area that we are trying to represent instead of trying to represent a small segment of the landscape with an even smaller sample of that landscape.  We also sample frequently, most often yearly, in order to quickly correct any quirks that we find in any given year.  Quirks are most often caused by differences in soil moisture and temperature from year to year.  By sampling frequently and at the same time of year each year we can pick up patterns in fertility change pretty quickly.  We believe that zone sampling is an accurate reflection of what we are trying to accomplish in a given field and takes out the randomness of grid sampling that is caused by spread patterns and blindly sampling a given area whether it accurately reflects the land or not. Here is another blog on our sampling philosophy.  

Using my Ipad Soil Sampling

I used my IPAD as my primary guidance tool in the field this spring.  It has worked better than anything else I have ever used.  I am using Ipad2 WIFI.  It does not have a data card, so it requires an external Bluetooth GPS.  I am using a Garmin Glo.  The app I am using is GISRoam.  At start up I sometimes have trouble with GISRoam recognizing the GPS on start up.  In other words, the cursor is not on the screen.   I sometime have to reboot two or three times.  I think it is a start up sequence problem, but once it is going it stays going. Battery life is 6 to 7 hours.  That is about all I can work anyway.  If you want to conserve battery you can put it on standby between stops.  Screen visibility is not great with the sun at your back, but you can darken lines and usually see it OK. I can visualize farmers using this setup to keep records on maps.  I have set up two customers already.

I recommend buying a model with a data card.  I think the newer models have better visibility too. 

Durability is good with the Otterbox.  I used it for an hour today in a light rain with no problem.  It also meets the test of time as I have sampled more than ever before.  Over all I rate it a 7 out of 10.  Nothing else I have gets higher than a 5.  There are flaws in all of them.  My previous blog had a rundown. 

Still Sampling Corn

We still have corn ground to sample, but most of it is not as big below.  I walked that 100 acre field.  Some of the corn was neck high, but the stand was very uneven because of wetness.  The good news is that this field was past the brittle stage so it was easy to walk through.  We try to sample corn within 2 or 3 weeks of planting but sometimes we miss some and get a good cardio workout.  The interesting part of sampling this was I used my Droid to keep track of where my zone boundaries were.  I used the Locus Free app and had to convert files to gpx format but it worked very well and you can't beat it for light weight.

Cold weather soil sampling

Today I soil sampled what I think is my last regular customer of the year.  We have heard a lot this fall in the ag media about how the dry weather might affect potassium soil test levels.  At this time of year, we start to think about how cold temperature might affect potassium soil test levels.  Soil Temperatures below 50 degrees Fahrenheit can cause reduced levels in the potassium soil test.  The reason we are worried about this is that results can be erratic because of environmental factors.  This is the reason experts say to test the same time of year each time you test.  This customer is usually one of the last of the year.  I have sampled him when it was so cold that I wore my Carhartt insulated coveralls.  I sampled him 11/27/2010, 11/16/2011 and today.  By sampling very close to the same time each year, we should be getting consistent results because we should be dealing with similar soil temperatures.  From looking at the results it looks as if there was some pretty serious potassium applied after the 2010 tests. 

New Equipment

Last night I purchased an IPAD2 that was a door buster at Walmart.  I am trying to get it set up for mapping and sampling in the field.  I will keep you up to date as I go. 

Weather Change Coming?

I saw 2 really big dust devils today.  They always look cool in the fall with corn leaves twirling around.  Often dust devils area precursor to a change of weather, but other than rain in the forecast Sunday and Monday, I am not sure what change we might get.  Could this signify Isaac affecting Midwest weather?  Maybe for the good?

On another note I was sampling harvested corn this afternoon.   Soil was not as moist as stubble beans sampled earlier this week, so the rain must have done some good to the corn.  I am not sure if it is dry enough to affect potassium or not.  Luckily we have past years data to judge from too. 

First Day of Fall Sampling Season

I had a client call me this morning to say I should start sampling his double crop soybeans.  They had about a 5% stand.  Topsoil was not wet, but recent rains and nothing growing had it moist enough that I did not have to use a hammer. I think it is probably moist enough that soil test levels will not be skewed.  Corn harvest was underway in the same area.  The auger wagon was not moving much, so I suspect very bad yields. 

Night Sampling

With Standard time in order and shorter days, I recently ran out of daylight trying to finish sampling a customer.  The headlights showed the way across the field and the GPS kept good track of my location.  Still seemed a little dangerous with ruts and rills in my path.  A curious neighbor came out to see what was going on too.   

Medora Again

I was in the same area as yesterday.  Yesterday the weather did not allow me to finish my work.  I think we had only 3/10 inch of rain today and in the corn stubble, it did not penetrate much.  The farm I was working on was a new one so I had to map it before sampling.  When I start out I look at key breaks and then try to figure out how to break the bigger areas into smaller sub areas to sample.  I did get all the major breaks mapped yesterday so I could subdivide with my GIS. 

Deer are moving around a lot with crops off.  That is a big safety issue in rural areas.  I hope the dampness has helped with the fire hazard.  I saw a burned combine with a lot of corn burned too.  Keep machinery as clean as possible and be careful about parking hot trucks in dry residue.

Sampling Philosophy

A recent question about spring/summer soil sampling causes me to give you a review of  previous blogs on how we sample.  Spring Sampling Season.

Here is one on Soil Grinding.  We strive to have the best possible samples to analyze. 

This blog summarizes my sampling philosophy.

This blog on sampling tools gets read somewhat regularly.

Samples need to be dried without heat for accurate results.  Here is my drying cabinet. 

Most of our sampling is done annually.  Here is why

Toughbook

Last week we took the time to take some photos of sampling activities for future reference.  On of the things we photographed include the Panasonic Toughbook that I have been using as my principal field sampling guidance for the last few weeks.  My Toughbook is loaded with Global Mapper and I have been mainly using a Wintec wireless receiver with it.  Except for an incident where I broke the screen the computer seems pretty durable.  The screen breakage was strictly carelessness.  This setup seems to be a good alternative to good way to some of the more expensive ag specific products out there.  Toughbooks are available on Ebay for around $400 the receiver can be had new for about $60 and the Global Mapper is around $300 on some websites.  A Ram-mount is also needed.  My friend Kelly has 2 of them he he has been using with FarmWorks software for the whole spring season.  We agree that they seem to be very durable.  It has added to our available number of GPS units.  If I use a white background with no aerials.  It is very visible.  This is as close to paperless sampling as we have come although, I like carrying the photo, because it is faster than turning on the photo and squinting at it on the computer.  A last thought is that with the territory we cover, it is good to have a fully functional computer in the field.  We are only as far away from the Internet as the nearest McDonald's.    We are hoping that is setup will last a year or 2 at least. 

Spring Sampling Season

It seems like fall has been the traditional time to pull soil samples.  Some people follow the logic that we want to know what is left for the next crop.  We want to know what the soil is like fertility wise, but a healthy soil should have enough nutrients to avoid a deficiency no matter what.  Since soil test levels vary through the year, we don't want to come up short at a critical time. 

We do about 2/3 of our sampling in the spring season, ideally from April 1 to June 15.  We sample after the wheat crop comes off in July.  Most of our spring customers put on lime and dry fertilizer in the fall so that they are ready for spring planting season.  If we spring sample, recommendations are delivered before harvest and fertilizer can be spread right behind to combine.  There is no waiting for results and recommendations.  Another advantage is that moisture conditions are good for sampling and fields are smooth for quick travel.  We try to sample fields at the same time each year where possible and it is kind of amazing how close we come to that.