- Author: Michelle Leinfelder-Miles
- Right source: selecting the fertilizer source that matches the crop need and minimizes losses,
- Right rate: applying the right amount based on crop need and nutrient availability through other sources,
- Right time: applying the nutrient when the crop can use it,
- Right place: fertilizer placement that optimizes the crop's ability to use it.
The four R's address management considerations (e.g. fertilizer program, irrigation), but site characteristics (e.g. soil, cropping system, weather conditions) also influence N recovery in the crop. Also important to improving crop N recovery is understanding barriers to adopting best management practices, such as costs or risks to crop quality or yield.
While the four R's articulate four principles for N management, the N cycle in cropping systems is complicated. Nitrogen can be introduced and lost by various paths. We generally add N with organic matter amendments – such as crop residues, compost, or manure – or with fertilizer. While organic matter amendments must be mineralized before the N is available for plant uptake, fertilizer N is readily available for plants to use. That said, plants generally take up N at different stages during their life cycle, and there is a risk for N loss if the N is applied or becomes available when the plants do not need it.
Technologies have been developed to mitigate N losses from cropping systems. These technologies are collectively known as enhanced efficiency fertilizers (EFF) and include additives, physical barriers, and chemical formulations that stop, slow down, or decrease fertilizer losses. Nitrogen stabilizers are one example and are fertilizer additives intended to improve crop N use efficiency and reduce N losses to the environment by interrupting the microbial processes that change N to its plant-available forms. We developed a trial to evaluate two N stabilizer products with the objective of determining whether the treatments improved corn silage yield or plant N status compared to fertilizer alone. We did not attempt to measure N losses from the system (e.g. leaching, denitrification), as these are very challenging to quantify.
The trial took place in San Joaquin County on a DeVries sandy loam soil. A description of the methods can be found in the full report. Sidedress fertilizer application occurred on June 21, 2018 and provided approximately 105 lbs N per acre (UAN 32). Four treatments were applied at sidedress, when plants were at V3-4 stage of development (Figure 1). The N stabilizers were applied at the label rates, and the treatments were: 1) Vindicate (Corteva Agriscience) at 35 fluid ounces per acre, 2) Agrotain Plus (Koch Agronomic Services) at 3 pounds per acre, 3) combination of Vindicate and Agrotain Plus at aforementioned rates, and 4) fertilizer-only, no stabilizer product (“untreated”). Treatments were randomly applied in three replicate blocks. Aside from the treatments, the trial was managed by the grower in the same manner as the field.
We evaluated soil N status, plant N status, and silage yield. Soil results are available in the full report. There were no statistically significant differences in plant N status or yield (Table 1). Mid-season (i.e. silking, R1) leaf N averaged 2.88 percent across treatments, and aboveground biomass N at harvest averaged 1.12 percent. At mid-season, leaf N from 2.7 to 3.5 percent indicates that the plant had sufficient N to carry the crop to harvest, and at harvest, aboveground biomass N from 1.0 to 1.2 percent indicates that the N fertilization program was adequate for maximizing yield. Thus, it appears that the trial was not deficient in N. Calculated to 30 percent dry matter, average yield across treatments was 38.8 tons/acre, and dry matter was 35 percent. There was a trend for the two treatments with Vindicate to have higher N removed than the two treatments without it, but the difference was not statistically significant.
In summary, N is part of a balanced, natural cycle in the environment and is the most important nutrient in cropping systems. Giving consideration to N management will help ensure that a greater fraction of the applied N is recovered in the harvested crop and not lost to the environment, and keeps growers in regulatory compliance. Enhanced Efficiency Fertilizers, such as N stabilizers, have been shown to improve crop yield in regions like the Midwest and the Northeast, and may help to mitigate N losses to the environment. In our trial, we evaluated the efficacy of N stabilizer products for improvements in corn silage yield or plant N status compared to fertilizer alone. Under the management and environmental conditions of this trial, we found no differences in yield or plant N status; however, plant and soil tests indicated that N was not limiting in the trial. If N was lost from the system, the loss was not large enough to result in N limitation in the control. Future study should test these products using different N sources and N rates (e.g. grower rate versus grower rate minus 50 lbs N/acre). It may be possible to reduce the fertilizer N rate without sacrificing yield.
This trial was made possible with the generous cooperation of Hank Van Exel and Van Exel Farms; Carl Bannon and Steven Colbert (Corteva Agriscience); Brad Schrenk (Simplot); Eric Ellison (Koch Agronomic Services); Nick Clark and Daniel Geisseler (UCCE); and Shirley Alvarez, Cheryl Gartner, and Dan Rivers (UCCE technicians). An in-depth report is available from my website. Please don't hesitate to contact me with comments or questions./span>
- Author: Michelle Leinfelder-Miles
Stand counts were made approximately two weeks after planting. The stand was assessed in the center two rows of each four-row plot, counting the plants along a 10-foot length. Bloom was assessed over the week of July 16th. While planting occurred on the same day as in 2017, the days to bloom was 68 in 2018, averaged across varieties, compared to 65 in 2017. This amounts to an approximate accumulation of 1230 growing degree days (GDD) in both years. In general, the temperatures were lower in 2018 compared to 2017. Over the course of the season, there were four days above 100⁰F, compared to a total of 14 days over 100⁰F during the 2017 season. (Temperature data is from the neighboring Staten Island CIMIS station.)
We monitored disease incidence and plant lodging in late September. Disease incidence, particularly Fusarium ear rot, was higher in 2018 compared to the two previous years. A sign of Fusarium ear rot is white fungal mycelium around the kernels. The disease is usually introduced to the ears by corn earworm or by thrips that travel down the corn silks at pollination. Incidence may be reduced in varieties with longer husks that prevent insect infestations. Planting earlier in the season may also reduce incidence, as the crop may reach pollination before insect pests are prevalent. Seed company representatives have indicated that Fusarium ear rot incidence was high in other parts of the state as well.
The table presents mean values for the three replicates. The statistical method used to compare the means is called the Tukey's range test. Varieties were considered statistically different if their P value was less than 0.05, or 5 percent. What this means is that when differences between varieties exist, we are 95% certain that the two varieties are actually different; the results are not due to random chance. Differences between varieties are indicated by different letters following the mean. For example, a variety that has only the letter “a” after the mean yield value is different from a variety that is followed by only the letter “b”, but it is not different from a variety whose mean value is followed by both letters (“ab”). Similarly, a variety whose mean yield is followed by the letters “ab” is not different from a variety whose mean yield is followed by the letters “bc”. Eleven varieties have a letter “a” following their mean yield, which means that those eleven varieties all performed similarly in the trial. In other words, based on this research, we cannot attribute numerical differences to varietal differences. The variety that had the lowest yield in the trial also had the lowest stand count. This may have been the result of the planter settings. Seed inventory records indicate that a standard bag of this variety weighed 54 pounds for 80,000 seeds; whereas, bags of other varieties weighed 39 to 44 pounds for 80,000 seeds. This larger-sized seed may not have dropped consistently from the planter in order to achieve the desired plant stand. Growers should contact the seed company with further questions.
Across varieties, there were also statistical differences in stand count, days to bloom, Fusarium ear rot, head smut, ear height, grain moisture, and bushel weight. The CV, or coefficient of variation, is the standard deviation divided by the mean, or a measure of variability in relation to the mean. For the diseases, the variability among the three replicates was very high.
Special thanks go to the cooperating growers, Steve and Gary Mello, and the participating seed companies. A printable version of these results is available from my website.
Table 1. 2018 UCCE Field Corn Variety Trial Results
Results for each variety are expressed as the average across three replications.
* Data were transformed for analysis. Arithmetic means are presented.
‡ Yield adjusted to 15% moisture.
† Larger seed size and planter settings may have caused lower stand and yield. Contact company representative for more information.
The Delta trial was on a Rindge muck soil, characterized by over 20 percent organic matter in the top foot of soil. Approximately 56,000 acres in the Delta have the Rindge classification (USDA-NRCS). Over the course of the season, the site received approximately 11.5 inches of rain, and the site was not otherwise irrigated. (Precipitation data is from the Staten Island CIMIS station.) The previous crop in the field was triticale during the 2016-17 season.
The results from the 2017-18 Delta trial are summarized in table form for wheat and triticale. The top-yielding wheat varieties were WB 7566 (4.6 tons/ac; 11.7% protein), LCS 12SB0224 (4.5 tons/ac; 11.6% protein), and UC Patwin 515 (4.2 tons/ac; 12.9% protein), and the top-yielding triticale varieties were WB Pacheco (5.9 tons/ac; 11.1% protein), NS Trical 115T (5.2 tons/ac; 9.3% protein), and NS Trical 158EP (4.8 tons/ac; 9.6% protein). Of note, there was volunteer triticale from the previous year that grew in the plot. We ended up only harvesting one replicate (of four) where we rogued the triticale by hand.
Since environmental conditions vary from location to location and year to year, we advise making variety decisions based on aggregated data. For example, the Delta trial had very wet conditions in 2016-17 when California received record-setting rainfall. While conditions in 2017-18 were closer to “normal”, we still suggest reviewing three-year summaries when making variety decisions. The results for the Delta tend to align better with those from the Sacramento Valley compared to the San Joaquin Valley. Thus, the Delta results are incorporated into the three-year summaries for the Sacramento Valley, available for wheat and triticale.
Over the past two years, the UC Davis team has developed web tools that allow us to view some of the trial data in a more interactive way. There are two websites – one with the multi-year summary data and another that summarizes each trial individually. We suggest using these interactive tools on a computer, rather than a phone.
Please let us know if you have questions about the trials or the web tools.