Corn requires only a fraction of this nitrogen during the seedling stage, but its needs escalate rapidly once corn reaches the V8 growth stage 8 leaf collar stage. Such rapid growth is equaled by few other crops, and requires a large supply of nitrogen to fulfill the demands of prolific green tissue development Figure 1. Figure 1. N uptake by corn. Adapted from Richie, et.
As the figure shows, corn generally requires over half its total N supply between V8 and tasseling VT , a period that may comprise only 30 days, depending on temperature and moisture conditions. Recommendations to sidedress N by V4 to V6 are to provide some margin of safety in case weather and soil conditions delay N application or N movement to the roots. Importance of Adequate N During Ear Fill In addition to its function in green tissue formation, nitrogen plays a crucial role in ear and kernel development.
A recent study of nitrogen translocation within the plant indicates that N moves to the ear from other plant tissues even prior to silking, apparently for the nitrogen-intense process of kernel embryo formation Ciampitti and Vyn, This study also reported that continued ear growth and yield accumulation from R1 to R6 is closely associated with N content in the above-ground plant tissues.
Perhaps most importantly, the study showed that continued N uptake during the ear-fill period can minimize the remobilization of N from vegetative to reproductive tissues.
This means that the plant does not have to cannibalize the leaves to provide N for kernel development when it can take up N from the soil during this period. This allows the plant to retain more green leaf area in late summer and early fall, which increases the duration of photosynthesis, carbohydrate production and grain yield.
In order to meet corn needs for adequate nitrogen at V8, growers must often contend with aberrant weather patterns that impact N management goals. Excessive rainfall can threaten soil nitrogen reserves as well as hinder resupply by ground equipment.
Excessively dry conditions can prevent applied N from moving from the point of application to the root zone of plants. Temperature and moisture conditions also impact the amount of N mineralized from the organic matter fraction of soils.
To help avoid weather-related pitfalls to corn N supply, growers can spread their risk by applying N at multiple times , or using products that help protect specific N fertilizers from rainfall-related losses. This is especially important on soils subject to N loss, such as sandy soils that are prone to N leaching, or heavier soils in high rainfall areas that may become saturated and subject to denitrification losses.
This approach to N management can also increase the bottom line by decreasing the total amount of N applied. Nitrogen may be applied by growers at several times during the year: in the fall, early spring preplant , at planting, and in-season sidedress.
Figure 2. Severe nitrogen deficiency symptoms are evident in this field that remained saturated due to excessive rainfall. These cool soil temperatures reduce the activity of nitrifying soil bacteria that convert ammonium to nitrate forms of N. Because of the extended period of time that this N is at risk of loss, fall application, if practiced, should be carefully managed.
In all instances of fall application, only ammonium sources of N should be used Murrell and Snyder, Early spring preplant application: Preplant N application is commonly used in areas where growers are able to complete this practice without delaying planting beyond the optimum window.
Because this N is applied well ahead of major crop uptake, it too is at risk of loss if warm soil temperatures and excessive rainfall occur. Application of ammonium forms of N can reduce loss potential. Depending on the time of application relative to planting, as well as expected weather conditions determined by climate history a nitrification inhibitor may also be advantageous.
At planting application: Though many planters are not equipped to apply fertilizer at planting, this method of application has certain advantages. When the field is fit to plant, planter N applications are sure to occur, unlike preplant or sidedress applications that may be disrupted by weather. However, there are limits on how much N can be applied at planting, due to concerns over effects on seed germination, as well as how much material can be reasonably carried on the planter.
In addition, applying fertilizer at planting slows the planting process to some degree. Liquid forms of N, such as UAN solution, are preferred for planter application. UAN solution can be combined with liquid starter or other liquid fertilizers to supply multiple nutrients to the crop. In-season sidedress application: In-season N applications allow for adjustments to planned N supply based on weather variations.
If wet spring conditions result in N losses, sidedress rates can be increased. If warm temperatures and moderate rainfall result in high N mineralization and an N-sufficient crop, sidedress rates can be reduced.
This process of determining crop sufficiency or need can be aided by various methods of soil testing or plant sensing Shanahan, In-season N applications can supply N to the crop near the time of maximum plant uptake. However, if wet conditions develop, sidedress applications may be delayed beyond the optimum application date. Extremely dry conditions can result in a delay in availability of side-dressed N to the plant.
Because of the risks associated with in-season N application, this practice must be carefully managed to reap its potential rewards. Soil fertility specialists often recommend that only one-third of total crop supply should be targeted for sidedress application. In addition, growers should be well-prepared to apply sidedress N as quickly as possible when the window of opportunity arises.
Finally, a backup plan should be in place for in-season application. If weather interferes with the originally planned application, a quickly implemented backup plan can help avert significant N deficiency and yield loss. The effect on yield of N application timing has been widely studied for decades. Common types of nitrogen timing studies include applications in the fall vs. Results of several studies are summarized below. Table 2. Summary of studies on the effect of N application timing on corn grain yield.
Adapted from Bundy, As Table 2 shows, the most common result of the N timing studies was no difference in corn grain yield between preplant and split application times. These rates are 11 lb higher than the rates in northern and southern Illinois, and 5 lb higher in central Illinois.
Those are modest changes because the data is added to a lot of existing data, but they illustrate how generating and adding new data keeps the guideline N rates responsive to research-based changes.
Remember that the MRTN rates and ranges generated by the N rate calculator include all of the N that gets applied, not just to the main application. This means that we should be able to take full credit for N from MAP or DAP, providing these are applied after soils cool in the fall about November 1 or later or any time before planting in the spring. If these P fertilizers are applied before soils cool in the fall, some of the ammonium will convert to nitrate and be subject to loss.
In about 90 percent of on-farm trials comparing N rates applied as ammonia in both the fall with N-Serve and the spring, we have found little or no difference in yield responses to N rate. Tile-drainage studies do show a little more N loss from fall-applied compared to spring-applied N, though, and we have found in a few cases either higher yields with spring-applied N or similar yields produced with lower rates of spring-applied N.
We have also found in a few trials the opposite—that fall-applied N can sometimes give higher yields or need less N to produce the same yield as spring-applied N. That is, having the N dispersed in the soil after application under better drier soil conditions in the fall may sometimes be an advantage compared to application into wetter soils in the spring. Wet fall weather like we had in likely means less chance of seeing such an advantage in We did not get many trials established last fall to make the comparison.
There is no reason to expect that the delay in N application in most Illinois fields so far this season will lower yield potential, but it will be important to keep a couple of things in mind as the planting season approaches.
Table 1 shows yield averages from 15 site-years over the past four years at four Illinois sites where corn followed soybean. Among the treatments with all lb N applied at planting, broadcast SuperU urea with both urease and nitrification inhibitors incorporated and ESN polymer-coated urea with extended release produced the highest yields.
Those that included N applied between the rows—especially NH 3 with or without N-Serve, which would have been accessible to the roots only once the roots grew out to the band, yielded a little less.
Adding nitrapyrin Instinct to UAN injected between the rows lowered yield a little, and those that had UAN surfaced-applied all yielded less: these may have lost some N or the N might have moved too slowly from the surface to the root zone to maximize yield.
Treatments with lb N split into lb at planting and 50 lb applied in-season generally yielded a little more than applying all of the N between the rows at planting Table 1. Otherwise, most of the treatments with lb injected at planting followed by 50 lb as urea with Agrotain broadcast at V5 or V9, or as UAN dribbled in-row at V5, V9, or at tassel VT stage did well. Waiting until V9 and dribbling all lb N as UAN at V9 was the lowest-yielding treatment, likely due to development of N deficiency whether visible or not that lowered yield potential in earlier stages.
Injecting all of the N mid-row at V5 yielded as well as injecting lb at planting and 50 at V5, which is counter to the idea that the crop needs more N early.
Another piece of evidence that the crop needs a good supply of N relatively early to avoid lowering yield potential comes from a part of the same N form and timing study reported in Table 1.
Averaged across 18 site-years, applying lb N at planting yielded 13 bushels more versus than applying 50 lb at planting plus 50 lb as injected UAN at sidedress, stage V The split-sidedress treatment yielded more than fall-applied N at most sites in , when June was very wet, but the split yielded less than fall-applied N at most sites in both and This shows that applying some of the N at sidedress can bring yields up close to those from all-early application of the same rate, but keeping back most of the N to apply in-season is more likely to decrease yields than to increase yield compared to applying all of the N before planting, including in the fall.
If we do sidedress, we need to apply at least half of the N where the roots of small plants can get access to it in order to prevent early-season deficiency that can result in lower yields.
We also noted that when we get really wet soil conditions in June after the crop has started to grow, like we had in , split-sidedress N can outperform all-early N.
Under these conditions, the crop may well need more N than we have or would have applied. Also, if the lower leaves have started to die off, the plant may not be able to take up and utilize added N. Corn Zea mays has a rich history as a component of North American and Mexican cuisine. Corn is hardy in U. Department of Agriculture plant hardiness zones 4 through 8.
It also grows well in warmer zones, such as in Mediterranean climates, when temperatures are between 60 and 80 degrees Fahrenheit. Sweet corn uses a large amount of soil nutrients as it grows, and it does best with multiple types of fertilizer added at different times throughout the growing season.
Compost or other organic matter, such as leaves or aged manure, is the best way to improve your soil's texture while also adding nutrients. Compost is a great addition to all types of soils. It improves the drainage in heavy clay soils and helps overly sandy soils retain more moisture. Experts at Utah State University Cooperative Extension recommend incorporating 2 to 4 inches of composted organic matter before planting sweet corn.
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