Achieving higher yields with fertilizer placement
Strategies for matching crop nutrient uptake requirements with fertilizer and placement technologies
Adequate crop nutrition is an often over-looked prerequisite of high yield corn and soybean production. Although we should strive for greater fertilizer use efficiency (yield per unit of input), it is clear that continued increases in yields will require more total nutrients, not less. For example, our research has shown that a 230 bushel/acre corn crop will take up about 100 lb P2O5/acre, and nearly 80% of this will be removed with the grain. This implies that at least 80 lb P2O5/acre needs to be supplied by a phosphorus fertilizer just to compensate for that removed by the grain. Besides phosphorus, nitrogen, sulfur, and zinc also have large (>50% of total plant uptake) grain requirements. As such, these four nutrients (N, P, S, and Zn) are particularly important and should be supplied in adequate amounts for high yield corn production. An additional challenge, however, is that some nutrients such as P and Zn are immobile in the soil. Therefore, placement should be considered in addition to rate.
Our corn omission plot trials are designed to quantify the contributions of management factors to yield in traditional and high tech management systems. Better crop nutrition is one of the factors that we routinely evaluate. In our initial trials in 2009 and 2010, we supplied 250 lb/acre of Mosaic's MicroEssentials SZ (MESZ; 12-40-0-10S-1Zn). As a result, an extra 30 lb N, 100 lb P2O5, 25 lb S, and 2.5 lb Zn were supplied per acre. This treatment was broadcast on the surface ahead of planting and shallowly incorporated to mimic a typical application method. Averaged across two years and a couple of sites, the extra fertility only improved yield (9 bushels/acre) under the high tech management system.
Experiences with fertilizer placement in 2011
In 2011, we had the opportunity to develop a research-scale fertilizer toolbar for placing dry products (Figure 1). This toolbar utilizes DAWN 6000 Universal Fertilizer Applicators for the row units, and a Gandy Orbit-Air Applicator to meter dry fertilizer products. The toolbar telescopes allowing us to place fertilizer in both 20-inch and 30-inch rows.
Twelve omission plot trials were planted in 2011 across five different sites. Placing fertilizer immediately ahead of planting slowed the planting process, but we were extremely pleased by the results. Across all of the sites, regardless of growth conditions, we observed a striking improvement in early growth, vigor, and uniformity of seedlings (Figure 2).
Most suprising was the fact that these improvements in growth occurred in soils that tested in the 'medium' to 'high' range for soil phosphorus. Typical recommendations would suggest that no additional fertilizer was required, yet we experienced these improvements in growth and ultimately yield.
Figure 1. Research-scale fertilizer toolbar.
Figure 2. Early enhancement of growth resulting from placed fertility. MicroEssentials SZ (12-40-0-10S-1Zn) was banded 4-6" directly beneath the row immediately ahead of planting at a rate of 100 lb P2O5/acre. The row on the right received the extra fertility while the row on the left did not.
Visual differences between plots receiving banded fertility and those without persisted through flowering (Figure 3). Fertilizer placement promoted increased plant height and more vigorous silk emergence. The positive effect on silk emergence could indicate that rooting of plants receiving banded fertility was enhanced during the dry conditions of summer 2011.
Figure 3. Comparison of a plot receiving no extra fertility (left panels) and an adjacent plot receiving 100 lb P2O5/acre banded 4-6" beneath the row (right panels). Silks of fertilized plots emerged more uniformly and with greater vigor.
Table 1. Contributions of four management factors (placed fertility, weather protected nitrogen, increased plant population, and strobilurin fungicide application) on yields of standard and high tech management systems. More information on the 2011 corn omission plot trials can be found here
Banded P fertility resulted in a yield increase of 14 bushels/acre when added to the standard management system, and a yield decrease of 17 bushels per acre when it was removed from the high tech system (Table 1). For more information on the standard and high tech management systems, please visit our corn omission plot page. These results suggest that significant yield gains can be achieved with fertilizer placement, even on soils that test >30 ppm for phosphorus.
So is banded fertility better than broadcast application of fertilizer? It makes some sense that placement would have an advantage for immobile nutrients like P. We are comparing broadcast and banded P fertilizer application in our 2012 trials.
Fertilizer placement experiments in 2012
We observed similar early-season responses to banded P fertility in 2012. Even with warm spring conditions that resulted in rapid emergence, there were clear differences between unfertilized and fertilized plots in fields that tested >40 ppm for P (Figures 4 and 5). Pre-harvest estimates of yield suggest that banded P fertility had a positive effect, especially at high plant density.
Figure 4. Comparison of untreated control (left) versus adjacent plot receiving 125 lb P2O5/acre banded 4-6" beneath row. V4-V5 plants growing at Champaign, IL in 2012.
Figure 5. Overview of field containing corn management trials at Champaign, IL in 2012. Differences in color and height of plots are associated with placed P fertility.
Along with our continued omission plot approach in which we are evaluating the value of banded P fertility, we are also comparing broadcast application versus banding at different rates. This trial encompasses placement (broadcast vs. banded), rate (0, 50, 100, and 150 lb P2O5/acre), source (MAP vs. MESZ), and a P availability enhancer (with and without P Max). Our hypothesis is that banded P fertility is superior to broadcast, particulary at lower application rates. Fertilizer treatments were applied in spring 2012. In fall 2012/spring 2013 we will be extending the trial to investigate the effect of application timing. Check back in winter 2012/2013 for updates on the results of the 2012 trial.
What about soybeans?
We believe that adequate soil fertility is widely overlooked in the pursuit of high yield soybeans. Balanced plant nutrition and fertilizer placement are some of the factors that we are studying in our Six Secrets of Soybean Success
project. In addition to P, nitrogen (N) and potassium (K) might also be critical to high yield soybeans. Unlike corn, in which most of the K is accumulated in the vegetative tissues, soybean has a large grain requirement for K. What about nitrogen? The soybean plant has the ability to symbiotically fix approximately 50% of its total N needs from the atmosphere. As yield levels increase, however, fixation may not be able to keep pace with the demand for N. This suggests that some N fertilization may be required for soybean production. A challenge, however, is that fertilizers containing nitrate or ammonium may inhibit nodulation and N fixation. Some evidence suggests that urea, however, can supplement the soybean plant's N requirement without inhibiting nodulation/fixation, as long as conversion of urea to other forms of N is inhibited. We are investigating placement of controlled-release urea sources as a strategy to increase soybean yield.
Related documents and links