The annual Delta field meeting will be held on Tuesday, October 4th starting at 10:00am. This year, the agenda includes topics on both field corn and sorghum. The meeting location is at the UCCE field corn variety trial plot off of Brunk Road on Tyler Island. Please see the attached flyer for more information. The agenda is as follows:

Agenda

10:00am        Field corn variety evaluation – preliminary results

10:15am        Variety traits for the Delta 

10:30am        Sorghum seeding rates for optimum productivity – preliminary results

10:45am        Viewing of field plots

We have requested CCA continuing education credits; light refreshments will be provided. Please contact Michelle Leinfelder-Miles, Delta farm advisor (209-953-6100) with questions.

 

The 2016 UCCE  grain corn variety trial was planted on April 27^th. The trial is located in the Delta on Tyler Island. Three replicate blocks of eighteen varieties were planted by air planter. The eighteen varieties included 16 varieties submitted by seed companies and two varieties submitted by the grower, which are presented in Table 1. Each replicate consists of four 30-inch beds on an average row length of about 1200 feet. Seed was planted two inches deep and six inches apart down the row, for an approximate planting density of 35,000 seeds per acre. The soil is a Rindge mucky silt loam with approximately 20 percent organic matter in the top 15 inches of soil. Approximately 55,600 acres in the Delta are described by the Rindge classification. Over the course of the season, we will evaluate the following parameters: stand count, days to bloom, fusarium ear rot, head smut, common smut, lodging, ear height, yield, and grain moisture at yield. Don't hesitate to contact me if you have any questions about the trial, and stay tuned to this blog for trial results at the end of the season.

Table 1. Field corn varieties planted in the 2016 UCCE field corn variety trial.

Brand Initials	Variety Number	Brand Name	Submitted by
CP	6525VT3P/RIB	Croplan	Stanislaus Farm Supply
CP	7087VT2P/RIB	Croplan	Stanislaus Farm Supply
DKC	62-08RIB	DeKalb	Monsanto/Ag Seeds
DKC	63-07	DeKalb	Grower
DKC	63-71	DeKalb	Monsanto
ES	7514VT2P	Eureka Seeds	AgReliant Genetics
ES	7667VT2P	Eureka Seeds	AgReliant Genetics
G	6708VT2P	Golden Acres	AgReliant Genetics
G	7601VT2P	Golden Acres	AgReliant Genetics
INT	6612GSS	Integra	Wilbur Ellis
INT	6474DGVT2PRORIB	Integra	Wilbur Ellis
LG	5701VT2P	LG Seeds	AgReliant Genetics
LG	5622VT2P	LG Seeds	AgReliant Genetics
P	31N27	Pioneer	Grower
SX	5543RR	Baglietto Seeds	Baglietto Seeds
TGY	8156GT	Tech Ag	Lyman Ag Group

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.

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).

According to the UC IPM Guidelines, wireworms may live three or more years depending on species, conditions, and food supply. Wireworm management in corn is generally by seed treatment or soil treatment at planting. Cultural practices – like crop rotation, flooding, or cultivation – are generally not effective against wireworms. Studies have shown that neonicotinoid seed treatments are as effective at controlling wireworms as organophosphates, the latter being linked to environmental and wildlife persistence. Neonicotinoids, however, are under increased scrutiny for possible off-target effects on bees. The objective of this study was to evaluate the efficacy of a new reduced-risk product called Lumivia^™ (active ingredient chlorantraniliprole) at different rates, in combination with other products, and in combination with polymers, which are used to help hold seed treatments in place. Lumivia^™ was compared to three commercial neonicotinoid products: Cruiser^® (a.i. thiamethoxam), Poncho^® (a.i. clothianidin), and Poncho^® Votivo^® (a.i. clothianidin + Bacillus firmus I-1582). This was the second year of evaluation. Complete reports from both years are available from my website.

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 30^th and October 14^th (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.