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In the spring of 2014 we initiated what was to be the first year of a three year project evaluating starter fertilizers for soybean production in the southern Great Plains. The first and second year was and is being funded by the Oklahoma Soybean Board.
Year one was a bit experimental in that with so many products on the market we needed some initial work to help focus the direction for years two and three. I also added a treatment which I knew would have significant negative impact, for extension reasons. Keep in mind two locations in a single year does not make an experiment nor provide enough information to draw a definite conclusion. It is however enough to learn some lessons from and for us to plan for our 2015 trials.
The 2014 trial consisted of 12 treatments, Figure 1 and Figure 2. In these treatments I wanted to see the impact of a standard practice, see if a specific nutrient may be more so beneficial, and evaluate a few popular products. The spring of 2014 started out dry so at one of our two locations we pre-watered. This was done by hauling water to the Lake Carl Blackwell (LCB) 1000 gallons at a time and pumping through sprinklers. The other site, Perkins, we delayed planting until we had moisture.
The two locations were also selected due to differences in soil fertility. The LCB site is has good soil fertility, with exception of phosphorus (P), and the Perkins site pH was an issue. I would have expected a benefit from adding P at both of these locations. Figure 4 shows the soil test results.
At LCB as expected some of the treatments (Thio-Sul) reduced stand, some unexpectedly reduced stand (Fe) and others had less impact on stand (APP 5.0) than expected. The growth at LCB was tremendous, the 30 in rows covered over very quickly and the majority of the treatments hit me waist high by early August (I am 6’0”). Many of the treatments showed greater growth than check. But when it comes down to it, grain pays and green does not. Statistically there were no treatments that out preformed the un-treated check, however the K-Leaf and 9-18-9 did make 3 and 2 bpa more than the check respectively. What I am hypothesizing at this site is that the added nutrients, especially those with high P levels, significantly increased vegetative grown and these big plants were delayed into going reproductive and they started setting pods later in much hotter weather. While riding in the combine I could see that the plots with compact plants with clearly defined rows out yielded those were the vines had crossed over and we harvested through more of a solid mat of mature plants. A hot August is not uncommon and I am curious on whether this trend repeats itself. If it does this may direct us into research evaluating ways to force/promote the reproductive stage to start in these big plants. Even if we can force flowering to start earlier, it’s unknown whether yields will increase or not.
The same trends in treatments reducing stand can be seen at Perkins, however the impact was less extreme. Perkins being planted later due to waiting on moisture forced a later flowering date and I believe reduced overall yields. But the addition of P at this low pH site definitely made a difference. While again no treatments were statistically greater than the un-treated check the 2.5 gpa APP, DAP broadcast, APP/H2O, and Pro-Germ/H20 treatments increased yield by 5.6, 4.2, 3.8 and 1.7 bpa respectively.
Take home from year one was that at LCB the addition of a starter fertilizer had little benefit and if done wrong could cost you yield while at the low pH site of Perkins an addition 2.5 gallons of APP did get a 5 bpa bump, but do to variability in the trial the increase was not statistically significant. This year we will drop some of the treatments and incorporate a few new treatments. Based on the current weather we look to potentially being able to start with better soil moisture at planting. Again do not take this work and significantly adjust any plans you have for your 2015 soybean crop. This is however some interesting findings that I wanted to share and make everyone aware of. Finally thank you to the Oklahoma Soybean Board for providing funding for this work. www.oksoy.org/
With all things holding constant the last canola trials of our project should be picked up by the plot combine Thursday 6-20-13. Before the first yield results comes to my desk I can tell you that we are learning a great deal from the trials this year. In particular the DAP (18-46-0) placed with seed trail that was supported by the Oklahoma Oilseed Commission. This past year at the no-till site in Perkins, which has a low soil pH, the check plots that did not receive any fertilizer, preplant or banded, did not survive the winter. Additionally at both of our locations, Lahoma (low soil test P) and Perkins, we have documented that oil content was reduced when phosphorus was left out of the treatment.
Additionally out of the four site years, that is two locations over two years, the addition of DAP with the seed in-row reduced stand. The graph below shows just how much stand was reduced on a relative basis. Relative stand is a way to compare the DAP treated to the Check (no DAP) which we assume is 100%. So if we look at the graph below the plots were at 75% relative stand (i.e. 25% loss) at approx 5 lbs N per ac. By about 15 lbs N the stand was down to 50%.
There are a few things to keep in mind first, in the case of these trials stand loss did not always mean yield loss. Canola is a great compensatory crop, if there is open space it will grow into it. I will have to run the final yield data to get more answers. These trials were planted on 15″ rows putting down 5 lbs seed per ac, or at least that was the target rate. Many have shown that the seeding rate does not have to be that high if sown properly. I believe in a few cases we may have actually benefited from thinning the stand. However if you were planting 2.5 lbs seed per acre a small loss of stand may be a bigger yield loss. This is one of the question we will have to answer in the future.
And finally it should be noted that canola is planted on a wide range of spaces 6″,7.5″, 12″, 15″, 30″ are some of the most common. As the row width changes the amount of N placed with the seed changes. In other words if the goal is 50 lbs DAP per acre you will put twice as much in a 15″ row than you do a 7.5″ row. The Table at the bottom provide a guide for equivalent rate based on 15″ rows. For example if your target a excepted stand loss of 25% (5 lbs N according to the Figure) but you are planting on 6″ row spacing the recommendation would be apply no more than 13 lbs N per ac in the row or 72 lbs DAP/ac (13/.18)