Godsey Ag

Starter Fertilizer for Corn in 2014, What do I need?

A lot of farmers have already pre-paid for starter fertilizer in 2014 but some serious thought needs to be given to what starter product fits the need. When corn was over $5 per bushel it was easy to justify some of the micronutrients in a starter mix. However, often times a lot of these ‘extra’ nutrients may or may not provide a yield response. With the profitability margin getting closer we need to take a long look to determine what nutrients are needed in a starter blend. The best place to start is with soil testing. Starter fertilizer blends should be based off of recent soil test.

Know and understand what the critical soil test levels are for each nutrient. The critical level is the nutrient concentration that indicates the division between a crop being responsive and non-responsive to applications of fertilizer. For example, the critical soil test level for P is 20 ppm. For soils with a P soil test greater than 20 ppm a response to P fertilizer is unlikely.  This is not to say that I would eliminate P from a starter mix in corn but you definitely can reduce the rate if your soil test P is greater than 20 ppm.

After you get a soil test back, consider your fertility needs and calculate the price per pound of N and P for several products. For example, 10-34-0 may have a $0.55 per pound of P, while a similar mix with Zn may bring the cost of P to $0.80 per pound of P. If the Zn is needed but if not it is expensive P.

One example of a nutrient that is often not needed every year in a starter mix is Zinc. The critical value for soil test Zinc is 1.0 ppm. If your soil test is above this level your crop is unlikely to respond to Zinc fertilizer. Pay attention to the soil test levels. If nothing is needed based on the soil test levels I would recommend just focusing on N and P for your starter.

Starter fertilizer is simply what the name infers; it is fertilizer to get your crop off to a quick start. When it comes down to it the nutrients most likely needed early in the season are N, P, and sometimes S. However, you still need to keep in mind the nutrient removal by the crop to help maintain productive soil but reduce or eliminate the unneeded nutrients in your starter mix.

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Data, data, data – what do I need to collect?

As we move more and more into the adoption of precision ag technologies we can easily become over-whelmed with the amount of data that is generated. Reading an article recently posted on PrecisonAg.com explaining the generation of enormous amounts of data as “big data”.  The phenomenon of big data can be good or bad depending on what side of the fence you are on. From a scientist point of view this big data is great but from a practical standpoint in real-world farming operations it can be a burden and easy for producers to look the other way. The questions that need to be asked are what do we need to collect, how do we store the data, and then finally how do we utilize the data to increase profits. A producer ultimately only wants to collect data that can help him make money in the future.

No doubt increasing profits is the most important but in order to get there you first have to have a plan for the what data to collect and how to store the data. If your goal is to manage on a 5 acre scale then some of the data and quality of data is not as important but if you want to manage every 60 ft2 of a field or less then quality and quantity of data is important. What is your goal for scale of management?

The bottom line is that you need to develop a goal for what you want to use precision ag technologies and its generated data for and go from there. If you want to vary seeding rate, collect a year or two of yield data and begin to develop seeding zones. The one thing that I would suggest is start collecting quality yield data ASAP. Often time’s producers do not have enough previous collected data such as yield data and this is the limiting factor in what you can and cannot do once you have all of the equipment in place.

Transforming the data into management decisions is not rocket science. On the surface I’m sure that it may seem overwhelming and I’m sure we as scientists have made it appear that you need an advanced degree to utilize the information but this is not the case. You simply need a goal(s) and someone to help you through the thinking process and perhaps in implementing the practices. Keep it simple for the first few years and only change one thing at a time. Go with the item that you feel will bring the biggest return (i.e. grid sampling, variable rate seeding, etc) and start there. This will also help in determining what data is needed to achieve this goal.

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Nitrogen Recommendations – Customizing for your own farm

In the previous blog we talked about different fertilizer strategies for P and K. In this blog I we will discuss the different approaches for N recommendations. Nitrogen fertilizer recommendations are a lot easier to interpret compared to other nutrient recommendations. Typically, to calculate a standard N fertilizer rate, you only need your yield goal and the N required per bushel or weight of crop to obtain your yield goal. The N required per bushel is often when differences come in when viewing recommendations from soil testing labs. You should ask what values they use and make sure they match with what you have seen on your own farm. For example, for corn I often use 0.8-1.0 lb N/bu to base recommendations off of instead of the traditional 1.2 to 1.3 lb N/bu. I have several on-farm data sets that support the reduced rate of N.

It is useful to know the organic matter (O.M.) content, soil sampling date, sampling depth (if more than 2 feet), the previous crop and the amount of straw residue remaining on the surface in continuously cropped fields. The following are some of the adjustments to a ‘generic’ N recommendation:

Adjustments to Standard Rate

1.  The level of O.M. in your field should relate directly to how much N is released during the growing season. Twenty pounds of available N per acre is expected to be mineralized during the crop year for each 1.0 percent soil organic matter in the surface six inches for warm season crops (e.g. corn, grain sorghum), while 10 pounds nitrogen per acre is expected to be mineralized for each 1.0 percent soil organic matter for cool season crops (e.g. wheat). Most N fertilizer recommendations were created assuming a typical O.M. content of 2%. If the O.M. content is 1% or lower, 15 to 20 lb N/acre may need to be added to your standard rate because less N will likely be released from the O.M. present. Conversely, if the O.M. is 3% or higher, you can likely subtract 15 to 20 lb N/acre from your standard rate.

2. If the previous crop was a legume, N rates can be decreased because some N from these high N containing crops will likely be released during the growing season. Different legumes have different credits so do some research on determining the appropriate N credit from legumes.

3. If fertilizer N will be surface applied to no-till small grain stubble that remains on the surface from the previous year, some N will generally be tied up (‘immobilized’). If light residue add 10 lb N/ac and increase up to 40 lb N/ac as residue thickness increases.

4. Sampling time is important to capture the true amount of N that will be available at seeding because some O.M. decomposition occurs during the winter months, releasing plant-available N in a process called “mineralization”. The closer you can sample to planting the better in accurately determining soil nitrate levels.  It is important to take the time to collect the 0-24” samples as often times you can have a tremendous amount of nitrate-N in the soil (50-150 lb N/ac).

Another factor that is important to consider is the efficiency of your applications, i.e. how many applications of N are made during the season. The more splits, the more efficient you are in utilizing the applied N. This can potentially decrease the lb of N/bushel that is required.

The only deviations from this traditional approach of N recommendations are sensor based approaches and methods to predict what N will be released during the growing season. These will be discussed in a later blog. Remember that the recommendations that come back are just recommendations and they need to be customized to your operation. I typically make several modifications when making fertilizer recommendations.

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What the heck, where did these recommendations come from?

Have you ever opened fertilizer recommendations and asked yourself where the heck did they come up with these? After just a few weeks into “officially” working with producers one on one I have been amazed with the wide-range of fertilizer recommendations that come back from labs. This raises the question of how labs come up with fertilizer recommendations. Sometimes recommendations have varied as much as three times as much as producers are used to seeing. Most differences come from P and K, so we will focus on these. Differences arise from the fact that some labs will recommend based on a ‘crop sufficiency’ approach while others follow a ‘build/maintain’ approach. Others will simply follow a crop removal approach.

Understanding the differences between these fertilizer philosophies will explain the difference that is often observed in fertilizer recommendations. Before we look at the approaches lets define what is often referred to as the critical level, which plays an important role in the different approaches. The critical Level is the nutrient concentration that indicates the division between a crop being responsive and non-responsive to applications of fertilizer is termed the “critical level.” For example, the critical level of K is 120 ppm or 240 lb/ac.  Let’s define each approach below in regards to P and K:

Crop Sufficiency– Sufficiency based fertility programs are intended to estimate the long-term average amount of fertilizer phosphorus required to, on the average, provide optimum economic return in the year of nutrient application. In some years greater amounts of nutrient are required for optimum yield and economic return, while in other years less than recommended amounts of nutrient would suffice. There is little consideration of future soil test values and soil test values will likely stabilize in the ‘low’ to ‘medium’ crop responsive range.

Build-maintenance– Build-maintenance recommendations are intended to apply enough phosphorus or potassium to build soil test values to a target soil test value over a planned timeframe (typically 4 to 8 years). In the case of P we will build and maintain the P soil test level between  20-30 ppm (40-60 lb/ac) and for K we will build soil test levels from 120-140 ppm (240-280 lb K/ac). When the soil test values fall within these ranges you will apply fertilizer based on crop removal rates in order to maintain the soil test values in this range. If the soil test levels are greater than these “build” levels then no fertilizer will be applied or only a small amount of starter fertilizer.

Crop Removal – Fertilizer is applied based on amount of nutrients that will be removed. This takes into account yield goal and amount of P and K that is in the grain or forage.

Understanding these fertilizer recommendation philosophies should help in interpreting results. Visit with the lab and ask what their approach to fertilizer recommendations are and make sure you are comfortable with that approach before sending samples. Also, remember that the recommendations that come back are just recommendations and they need to be customized to your operation. I typically make several modifications when making fertilizer recommendations. Some of the things that alter recommendations are initial soil test levels, if land is owned or rented, no-till vs. conventional till, etc. Having a nutrient management plan is important in improving nutrient use efficiency.

Nitrogen recommendations can be even more confusing but we will cover these in a later post.

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Variable Rate Seeding for Corn

We are a few months away from the 2013 corn planting season but it is time to start thinking about the opportunity to vary the seeding rate. If you are equipped with the capability to vary seeding rate at planting it will pay in most situations. Often times the seed savings is minimal but the increase in yield potential can be several bushel. Increased in yield potential can be seen in low and high yielding areas of the field. Increases of only a couple bushels mean a lot of additional revenue at today’s market prices.

I believe that variable rate seeding will pay in both irrigated and dryland systems. In the past where we have done variable rate seeding we have increased yield on average about 5% by matching the correct seeding rate with each ‘yield potential’ zone. A lot of data can be used to create prescription maps but perhaps the best is past yield history and producer knowledge. One thing that is important to do is put check strips out at several locations within a field so at the end of the year we can go back and evaluate yield response to population. This information can be used in the following season to fine-tune the prescription map. Most times producers know what their ideal population range is but it may change from year to year depending on the hybrid you are planting. If you are interested in variable rate seeding please let us know. There is potential for variable rate seeding with other crops as well. We will discuss some of those in later blog entries. Prices typically range from $1-4/acre depending what data is available and how we delineate zones.

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Is grid soil sampling better than zone sampling?

Grid soil sampling versus zone management sampling has been debated for several years. Both have their advantages. In my opinion, zone management sampling is best used when zones can be based off of historic yield potential (yield maps or farmer’s knowledge). Zone management based sampling should be cheaper than grid sampling because you are taking fewer samples per field. In contrast, with grid sampling you usually collect more samples per field in order to get a higher resolution or better “picture” of variability within the field. If low pH is a concern I would definitely recommend grid sampling to better define the areas that need lime and those areas that do not.
In most cases, both grid soil sampling and zone management based soil sampling is a big improvement over uniform management! The debate over grid vs. zone comes down to the farmer’s goals and each individual field. If you suspect a large amount of variability scattered throughout the field then grid sampling will be best. However, if you have large areas with a uniform yield history then zone sampling will save you money.

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Welcome to the GPA Blog!


We are very excited to announce the opening of Godsey Precision AG! Through our blog we will provide timely unbiased information that centers around making educated decisions on using precision ag technologies in your operations. A tremendous amount of thought and research has gone into developing services for the farmer. Through 7 years of working in extension I have observed several precision ag services that are simply designed to sell products but do not increase the farmer’s bottom line. This has been frustrating since these technologies are relatively new and often times this is the first exposure for many farmers. The end result is the farmer getting discouraged with precision ag. We are independent and do not have a vested interest in selling products!

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