- Author: Michelle Leinfelder-Miles
- Contributor: Brenna J. Aegerter
The meeting showcased the UC Davis wheat and triticale variety testing program for the Delta, and presentations were given by UC Cooperative Extension and USDA-NRCS scientists. UCCE Grains Specialist, Mark Lundy, demonstrated a soil nitrate quick test and how it can be used in small grains fertility programs. UCCE Cropping Systems Specialist, Jeff Mitchell, described tillage research taking place at the UC Westside Research and Extension Center and demonstrated how no-till plots had better soil aggregation and tilth than conventionally tilled plots. USDA-NRCS Director, Margaret Smither-Kopperl, described winter and summer cover cropping trials at the Plant Materials Center in Lockeford, CA.
Additionally, Brenna Aegerter and I described an upcoming cover cropping trial that we will conduct on Staten Island. We were awarded a CDFA Healthy Soils Program grant with our farm advisor colleagues in the Sacramento and San Joaquin Valleys – Sarah Light, Amber Vinchesi, and Scott Stoddard – along with Jeff Mitchell and Will Horwath at UC Davis. On Staten Island, we will trial legume cover cropping versus no cover cropping treatments for soil health properties, greenhouse gas emissions, and grain yield from 2018-2020.
The trial will take place in a field that is in small grains (wheat and triticale) rotations, with soil classification Valdez silt loam. Cover cropping will take place in the summer months following the small grains harvest. Initial soil sampling will take place after wheat harvest and subsequent tillage. We will take baseline soil samples, measuring bulk density, pH, salinity, total C and N, aggregate stability, infiltration, and active C (a measure of the carbon available as an energy source for soil microbial communities) in the top foot of soil. At deeper depths, we will also test bulk density and total C. We will soil sample each fall, at the end of the cover crop season, to evaluate changes in soil properties over the three years. Greenhouse gas (N2O and CH4) monitoring will allow comparative evaluations of cumulative emissions between the soil management systems. Small grains yields will also be determined.
We look forward to this trial and will share results as we have them. We want to thank Dawit Zeleke and Morgan Johnson at The Nature Conservancy's Staten Island, Margaret Smither-Kopperl and Valerie Bullard at the USDA-NRCS Plant Materials Center, and Tom Johnson at Kamprath Seed for their collaboration on this trial.
For more information on UCCE or USDA-NRCS programs, please visit the following blogs and websites:
UC Sacramento Valley Field Crops Blog
- Author: Michelle Leinfelder-Miles
- Contributor: Mark Lundy
I have received a couple inquiries from Pest Control Advisors about wheat that is showing leaf tip yellowing and burning (Fig. 1). Their suspicion is frost injury, and with the weather we have experienced over the last several weeks, their suspicion is likely true.
There isn't a hard-fast rule of when frost injury will occur because several factors influence its occurrence and severity. The factors include the temperature but also the duration of cold exposure, the plant growth stage, and the growing conditions. The UC Small Grains Production Manual (see page 101) states that injury may occur with temperatures at or below 35⁰F and that even just a couple hours of exposure is enough to cause injury.
Below (Fig. 2), I present temperature data from the last month from a few local CIMIS stations. Remember that in early-February, daytime highs were getting above 70⁰F. By mid-February, however, minimum temperatures were low enough to cause frost injury, and hourly data (which I am not showing but is available from the CIMIS website) shows that temperatures below 30⁰F often spanned several hours over many nights in late-February.
The plant stage of development is critically important to how a crop may be injured from frost and how it may overcome injury. At tillering, leaf yellowing and tip burning will be the obvious symptoms. At this stage, however, yield impact will likely be slight, if any. That is because the growing point of the tillers is close to the soil and protected from the cold. When warmer weather resumes, the plants may be able to continue tillering, particularly in thin stands where there is space to fill, and overcome the injury. In the jointing stages, in addition to the leaf yellowing and tip burning, some leaf or stem lesions may be apparent. There could be moderate impacts on yield if the growing points of the tillers have been injured. Look for a chlorotic or dead leaf in the whorl. Also, try splitting the stem with a razor blade at the growing point. This picture from Texas A&M University shows how to do this. If the growing point (at the arrow) appears white, brown, or water-soaked, then there has been frost injury. Once the crop gets into the reproductive stages of growth, it becomes more sensitive to injury with bigger repercussions for yield, but luckily, I think most of the fields in our region aren't yet to these later stages of development.
Keep in mind that there are field and other growth conditions that may lessen or worsen the severity of frost. Low parts of the field where cold air settles will likely show more injury. Fields that were planted earlier in the fall, or earlier-maturing varieties, that are in a later stage of growth will likely show more injury. Crops that have had good moisture and nutrient conditions may also show more injury. With one of the inquiries I received, the field had been fertilized about a month ago, and given the warm daytime temperatures we had at that time, those plants were likely resuming growth and probably got hit by the frost all-the-more. Crops that have been moisture stressed, however, may have been hardened and not show as much injury.
So, what now? Again, growers and consultants with crops in the jointing stages who are seeing leaf tip yellowing may wish to split some stems to observe whether there has been injury to the growing points. If this has occurred, there is nothing that can be done to “save” those tillers, but it might provide some insight into potential yield impact. If stem lesions appear, be on the look-out for disease infections but also lodging later in the season. Unfortunately, the most telling symptom will appear after heading when grain doesn't fill. Don't hesitate to reach out to me or your local farm advisor if you have questions about frost injury.
- Author: Michelle Leinfelder-Miles
- Contributor: Mark Lundy
- Contributor: Nicolas George
Fall has arrived, and for many crops, this means that it is harvest season. For small grains, however, the season starts anew. The UC Davis small grains variety evaluations are conducted across the state, including a site in the Delta. The results of last year's evaluations are now available, and we invite you to take a look as you prepare to plant your new crop.
To understand trends over time, we suggest reviewing the 3-year summaries, which are available from the link “Yield and Protein Summary” for common wheat and triticale. These summaries indicate which varieties performed consistently well over time. For these summaries, the Delta is grouped with other Sacramento Valley locations. The data indicated that the varieties performed similarly between the Sacramento Valley and the Delta, compared to the San Joaquin Valley and the Delta. This is probably due to similar climatic considerations, like rainfall and temperature. The 3-year summaries rank the varieties for both yield and protein. In the future, rather than tables, the research team will develop an online tool to assist with variety selection that will take both yield and protein into account. Stay tuned for more information on this tool.
Keep in mind that disease ratings are important considerations. Disease ratings are found here, where “S” indicates susceptible varieties and “R” indicates resistant ones. Additionally, some of these varieties are in initial stages of testing, so not all of them are commercially available. Look for whether the variety is “released”, which is indicated on the data tables.
Barley and durum wheat were also evaluated at certain locations but not in the Delta. We will continue trialing small grain varieties in the Delta in 2018.
- Author: Michelle Leinfelder-Miles
I recently visited a wheat field with a crop consultant. The consultant was confident that the wheat had Septoria Leaf Blotch disease (Septoria tritici, Mycosphaerella graminicola); he was familiar with the leaf symptoms (Figure 1) and the region has a history of problems with Septoria. He was also noticing, however, some lesions on the glumes (Figure 2), and wondered if there was another disease present. It turns out that the lesions on the glumes are also a symptom of Septoria and can be seen if wet weather occurs after heading.
Septoria is a serious problem of wheat because, as lesions coalesce, particularly lesions on the flag leaf, it can reduce the photosynthetic capacity of the plant and reduce grain filling, thereby reducing yields. Septoria is most problematic in rainy years and in early-planted fields. Early-planted fields have a longer period of exposure if the disease is present on crop residues or volunteer plants. Crop rotation can help manage against Septoria in future plantings, but planting more tolerant varieties and properly-timed fungicide applications are also good management practices. Septoria ratings are not a regular part of the UC statewide variety testing program, but ratings are available from 2011 and 2012. (On the previous links, click on Table 3.) Fungicides, like Mancozeb and Propiconazole, should be applied between tillering and heading, with the purpose of protecting the flag leaf. Septoria only infects wheat, so other small grains like barley, oats, and rye are not affected by the disease.
The field that I visited was likely an early-planted field, and the disease seemed worse on the edges and on the south side of berms where the conditions were likely a little bit warmer and the plants advanced a little bit faster. The field is completely headed out, and the grain is in the milk stage, nearing the soft dough stage. The million dollar question is, with the forecast of rain later in the week, is it worthwhile to spray a fungicide? If it does rain, the disease may spread, showing more lesions on the flag leaf. With grain at the milk to soft dough stage, the grain may be able to mature even if the disease gets worse. Making the decision on whether to apply a fungicide at this time is a hard call to make for a farm advisor or consultant because it really comes down to dollars and cents. In this case, however, product labels say not to apply the product after 10.5 Feekes, or full heading, so this particular field is beyond the stage when a fungicide should be applied.
Information on products and practices is for educational purposes only and does not constitute an endorsement or recommendation by the University of California.
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- Author: Michelle Leinfelder-Miles
It is the time of year when the harvest of our summer crops has concluded. Some growers may be planting small grains, and let us hope that winter rains nourish these crops. I received an inquiry from a grower at the end of harvest regarding nutrient removal with the harvest. This grower, in particular, had questions about how much potassium (K) is removed with the grain and straw/stover of a crop. Alternatively, we can think about how much K is added to the soil when crop residues are incorporated. This grower farms on a low K soil in the Delta and wants to know how much K could be available for his tomatoes next season, a crop that has high K demand.
The California Department of Food and Agriculture Fertilizer Research and Education Program (CDFA FREP) provides crop fertilizer guidelines for nitrogen (N), phosphorus (P), and K. These guidelines were developed by Daniel Geisseler, Nutrient Management Specialist at UC Davis, using research results from California and elsewhere when California information was not available. The guidelines for wheat state that the concentration of K in the grain is 0.4-0.5%, and the concentration of K in the straw is approximately 1.5%. What this means is that for a wheat field that yields 3 tons/acre, 24-30 lbs K/acre would be removed with the grain (0.004 or 0.005 * 6000 lbs grain/acre = 24-30 lbs K/acre). Likewise, 90 lbs K/acre (0.015 * 6000 lbs straw/acre = 90 lbs K/acre) would be removed with the straw if the straw is not incorporated, assuming that approximately one ton of straw is produced per ton of grain. For corn, the grain is approximately 0.4% K, and the stover is about 1.5-2.5% K. Whether the corn is harvested for grain or silage, approximately 40 lbs K/acre will be removed with the grain at harvest (assuming a 5-ton crop). If the corn is harvested for silage, or if the stover is removed, then approximately 150-250 lbs K/acre will also be removed with the stover (again, assuming a 5-ton crop). If the stover is incorporated, then the grower is returning this amount back to the system.
The grower also asked how soon the K would be available for a subsequent crop (like his tomatoes) if he incorporates the crop residues. To get an answer for this question, I consulted with UC Davis graduate student, Jordan Wade, and UC Davis professor of biogeochemistry, Will Horwath. Both of them surmised that the K should become available fairly quickly because K is not a structural component of the plant. Contrasting K and N, for example, K is floating around in the cells in a soluble form; whereas, N is bound with carbon, forming structural parts of the plant. K is in a form that plants can use (it does not need to be mineralized into a plant-available form, as with N), so when the crop residue is incorporated and breaks down, the K should be readily available for plants, unless it gets adsorbed to soil particles.
In agricultural areas where little-to-no “maintenance” K has been applied over the years, it is possible that crops have depleted soil K. The FREP guidelines recommend applying K to wheat fields if the pre-plant soil test is less than 40 ppm. In corn, it is recommended to apply K if the pre-plant soil test is less than 50 ppm. It is recommended to take pre-plant soil samples for nutrient testing before each new crop.