- Author: Michelle Leinfelder-Miles
Back in October, a Delta farmer presented me with this scenario: The California Division of Boating and Waterways would be clearing water hyacinth from some Delta waterways. They asked the grower to receive some of it onto his land. Could there be any potential problems with receiving it? Let's take a step back from this scenario to understand why the Division would be looking to dispose of water hyacinth in this way.
According to the Division, water hyacinth was introduced into the Delta from South America over 100 years ago. It can be considered an attractive plant for its purple flowers, but its floating nature and potential to double in size every ten days under warm weather conditions makes it a difficult plant to keep under control in the Delta. It can impact recreation and commerce because mats of it can grow up to six feet thick, restricting boat traffic, and it can impact agricultural operations by clogging intake pumps. It also impacts the Delta ecosystem by out-competing native plants, blocking light into the water, and reducing dissolved oxygen.
The Division conducts an aquatic weed control program in the Delta, and additionally, UC Davis researchers are conducting projects to evaluate methods for controlling water hyacinth. Nevertheless, when water hyacinth spreads as rampantly as it has in recent years, the grower's scenario deserves some consideration as a way to mitigate the problem. After consulting with UC Cooperative Extension colleagues, we surmise that there probably would not be much harm in this grower accepting un-composted water hyacinth onto his fields. My colleagues and I believe that this would work best in warm weather so that the water hyacinth would dehydrate and decompose quickly. (Back in October, we still had some warm weather. It would be less advisable now that the weather has cooled.) Before having the material applied, we suggested that a wet sample of the material be dried, the percent moisture calculated, and the dried material tested for nutrient, salt, and metal content, so that the grower knows the concentrations of these in the plant material. The grower should also ask the total wet weight of material that would get applied so that he can calculate the total amount of nutrient, salt, or metal that would be applied to his land. We do not suspect any toxicities, but testing the material would help to confirm that. We do not suspect this would be an economical practice if the water hyacinth needed to be transported over a long distance because of the heavy fresh weight of water hyacinth. Provided there are no nutrient, salt, or metal concerns, and if there are fields adjacent to clogged waterways where growers are willing to accept the material, this could be a way for the grower to add organic matter to his soil and for the Division to reduce the presence of an aquatic pest.
- 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.
- Author: Michelle Leinfelder-Miles
Wireworms are the soil-dwelling larvae of click beetles. They feed on the seeds and roots of various crops and are a particular pest of field corn in the Sacramento-San Joaquin River Delta region (Figure 1).
Two trials were conducted in 2015 – one on Staten Island and one on Tyler Island. The soil type at both trial sites is a Rindge muck, which characterizes approximately 57,000 acres in the Delta. The Rindge muck is high in organic matter and considered very poorly drained, and thus, it was a good soil for these trials because the soil stays cool and damp into late spring and early summer. Both sites have heavy wireworm pressure, according to the growers, and were planted with corn the previous year. The Staten Island trial was planted on April 15, 2015, and the Tyler Island trial was planted on June 9, 2015, both having four replicate blocks.
We evaluated growth parameters starting at about a week after planting for a period of about six weeks. Growth parameters of interest were emergence, stand count, vigor, damaged plants, dead plants, and height. Additionally, on the second week of evaluations, ten seedlings were lifted. Dead and live wireworms were counted on the seeds, roots, and surrounding soil, and the seedlings were given a visual health rating. The trials were harvested on September 30th and October 14th (Staten and Tyler Islands, respectively). Harvest parameters included a plant count, yield, grain moisture, and bushel weight. Additionally, at the Staten Island trial, Johnson grass plants were also counted because weed pressure was high.
Growth results are described in the online report. Yields at the Staten Island trial were highly variable, and both wireworm and weed pressure may have contributed to the variability (Table 1). Johnson grass pressure was especially high in treatments where plant stands were compromised by wireworms or birds. High weed pressure can be a consequence of poor wireworm control because stands that are compromised do not provide the consistent shading to out-compete weeds. Yields can suffer as a result. The Lumivia™ + Cruiser® treatment yielded the highest, and Lumivia™ 750 yielded the worst, even lower than the untreated control. The poor result of Lumivia™ 750 may be explained by uncontrollable factors, namely, bird damage and high wireworm pressure. The polymer treatments that were tested at the Tyler Island site showed no yield benefits over the non-polymer treatments and yielded similarly to the commercial standard, Poncho® Votivo® (Table 2).
The trial results illustrate that growers have several options for managing wireworms. Across both trial locations, results suggest that Lumivia™ 250 + Cruiser® 250, Lumivia™ (500 or 750) in combination with bifenthrin 125, and commercial standards Poncho®, Poncho® Votivo®, and Cruiser® provide good control against wireworm in the weeks after planting when corn is in the seedling stages. While we saw few statistical yield differences, the control and resulting better stands have the potential to improve yields over non-treated seeds. The two Poncho® products are commercially available from Bayer CropScience, and Cruiser® is commercially available from Syngenta. Lumivia™, a Dupont product, is not yet commercially available as a corn seed treatment in California, but if it were to become so, it would provide growers with an alternative to the neonicotinoid treatments. When making decisions on products, growers should consider their wireworm pest pressure and other soil-dwelling pests that could limit their production. Growers should also consider which seed treatments they have been using and whether those are still controlling pests. If not, rotating to a different chemistry might be a way to bring pests back under control. Integrated pest management practices recommend rotating chemistries for insect resistance management.
- Author: Michelle Leinfelder-Miles
California agriculture is successful, in large part, because of the Mediterranean climate and irrigation infrastructure. While irrigating crops is the norm, there are growers who practice dryland, or rainfed, farming. These growers utilize winter rainfall to produce the crop.
Recently, I received an inquiry for dryland farming resources available from UC. With the help of other farm advisors, we located some resources, all of which are available online. There are two cost and return studies produced by UC Cooperative Extension and the UC Davis Agricultural and Resource Economics Department. One of the studies is for dryland safflower and the other is for dryland oat hay. The cost and return studies are intended to guide growers in preparing budgets and making production decisions based on practices that are typical for specific crops and regions of California. The UC ANR Small Grain Production Manual references rainfed systems and how they may differ from irrigated production in terms of seeding rate, fertility and tillage. Additionally, the University conducts statewide wheat and barley performance trials, and some trial locations include rainfed treatments. See the Agronomy Progress Report No. 318 for performance trial results.
- Author: Michelle Leinfelder-Miles
I was speaking with a colleague a few weeks ago about field drainage in the Delta. Our conversation reminded me of a farm visit that I made a couple of years ago. I visited a corn field that was not growing well, and sections of the field had standing water. I consulted with UC Water Management Specialist Emeritus, Terry Prichard, on what this grower could do to improve drainage. I wondered about installing drainage tiles. The irrigation specialist did not recommend installing drainage tiles in the Delta. The high organic matter soils are so fine that the perforations in the tile just plug up. He also did not recommend a deep plow because some Delta soils have a layer of “blue clay.” It is not actually clay but it is anaerobic soil (which is what makes it blue) that has never been near the surface. The irrigation specialist had once visited a field that had been deep plowed and brought up blue clay. The field became completely unmanageable.
What the irrigation specialist did recommend was to dig 4-foot (deep) drain ditches. These would run parallel to the furrows and should be about 500 feet apart. These ditches would connect to another ditch that runs to the main drain of the island. These dimensions are not a prescription for all Delta sites, but they could give landowners a general guide for managing drainage, and in the case of the corn field I visited, make wet fields farmable. Each 4-foot ditch will result in about 10 feet of “wasted” (non-farmed) space, but having these ditches (and keeping them clean) is the only way to get the water out of the soil profile and off the field.
Before any effort is put into digging ditches, it would probably be beneficial, particularly for new landowners, to see from an internet mapping interface if there are any lines in their fields that would indicate past ditches or different soil types. If previous landowners leveled the land, they may have filled in drainage ditches.