The 2017 season was marked by weather extremes, including record winter rainfall and high summer temperatures. Despite those, Delta rice growers generally observed an average to above-average season. Total acreage for the Delta south of the Yolo Bypass was roughly 2900 acres. For some growers, acreage was up because they were able to get ground preparation done early, but for others, acreage was down because the ground was late to dry out. Most of the Delta acreage is in San Joaquin County, with a few hundred acres in the “tail” of Sacramento County. The acreage was entirely drill-seeded, as is typical for the Delta, and planted with M.206.

Annual rainfall (October 1, 2016 to September 30, 2017) for the region varied greatly by location. CIMIS stations for the south Delta reported rainfall from 16 to 20 inches, but stations in the north Delta reported 28 to 38 inches. Most of this rainfall fell in October through January. Spring rainfall lingered into the month of April, but accumulation of at least a tenth of an inch ceased by mid-April. Given the high organic matter content of many Delta soils, fields generally dried out for on-schedule planting in late-April through early-May, with few exceptions.

Figure 1. Armyworm bucket trap catches were highest in late June.

Cooler temperatures in the Delta, compared to the Sacramento Valley, make the Delta a challenging place to grow rice. The summer of 2017, however, brought many days over 100⁰F. This varied greatly by location, with some areas in the north Delta having approximately 10 days over 100⁰F and areas of the south Delta having 25 days over 100⁰F, according to CIMIS stations. Hot days meant warmer nights, which was a good thing for Delta rice culture. Delta rice can experience blanking due to low night-time temperatures, influenced by Delta breezes. We expect blanking to occur when the developing pollen grains are exposed to night-time temperatures at or below 55⁰ F for several hours. Across four Delta CIMIS stations, the average minimum temperature from August 1^st to September 15^th was 60⁰F.

Harvest was generally on-schedule and occurred from late-September to early-October. Anecdotally, yields were up and averaged over 90 cwt/acre. Growers suspect that the higher summer temperatures (including higher night-time temperatures) resulted in less blanking and higher yields.

Overall, Delta rice growers had an average to above-average year as we close out 2017. Let's hope for a similar 2018.

(There was an error in the previous version of this blog post. The error has been corrected here and in the full report, available from my website.)

The purpose of this trial was to better understand optimal seeding rates for grain sorghum grown in the Sacramento-San Joaquin River Delta – a unique agricultural region known for its fertile, organic soils, shallow groundwater, and cooler climate conditions. The trial was planted in the Sacramento-San Joaquin Delta, on Tyler Island in Sacramento County. The soil is a Rindge mucky silt loam with approximately 20 percent organic matter in the top 15 inches of soil. The Rindge series is a mucky peat soil down to about 60 inches, and approximately 55,600 acres in the Delta are described by the Rindge classification. The plot was planted on May 20, 2016 using a John Deere cone planter. Seed was planted approximately 2 inches deep. The trial was a white sorghum variety, Eureka Seeds 3292, which was the grower's variety. The variety has 16,000 seeds/lb and 85 percent germination, according to the label. Five seeding rate treatments (5, 6, 9, 12, and 15 lbs/acre) were replicated over four blocks positioned down the rows. The seeding rates are expressed as plant populations in Table 1. (The number of sorghum seeds/lb is highly variable across varieties. For this reason, when determining seeding rates, growers should first determine their desired plant population. A worksheet for calculating seeding rate from desired plant population is available from the full report.) Each plot consisted of four rows (30-inch row spacing) that were 45 feet in length. The previous crop in the field was wheat. Subsurface irrigation by “spud ditch” sub-surface irrigation was employed twice. The field was fertilized at planting with 35 gallons/acre of 8-24-0 with ½ percent of zinc. The field was cultivated one time, and Maestro 4EC (8 oz/acre), AAtrex 4L (0.75 pint/acre), and Crosshair (4 oz/acre) were applied for post-emergence weed control in mid-June. The plot was harvested on November 14, 2016 using an Almaco research combine, harvesting the center two rows from the four-row plots.

Trial results are presented as plant establishment characteristics (Table 1), plant maturity characteristics (Table 2), and yield (Figure 1). The tables and figure present mean values for the four replicates. Tukey's range test was the statistical method used to compare the means. Varieties were considered statistically different if their P value was less than 0.05, or 5 percent. Differences between treatments are indicated by different letters following the mean.

The estimated plant populations for the treatment seeding rates were calculated using the number of seeds/lb and percent germination for this variety. Stand counts were made as the number of plants/10-foot row length on June 1^st and June 16^th, and these counts were scaled up to plants/acre. Stand counts were as expected - higher counts for the higher seeding rates. Stand counts for all treatments decreased from June 1^st to June 16^th, but stand counts remained on target with the estimated plant population for the 5 and 6-lb seeding rates. Weeds were also counted in the month after planting and in the month before harvest (data not shown), but overall weed pressure was very low at this location.

There were no differences in the number days to flowering among treatments; however, there were differences among treatments in the other maturity characteristics. The higher seeding rate plots had taller plants with longer panicle exsertion (the length of the stem from the top leaf to the bottom of the panicle), which may suggest that at these higher densities, plants were competing with each other and growing taller. Panicles were longest in the 5 lb seeding rate and statistically longer than the panicles in the 12-lb and 15-lb rates. There were no statistical differences in grain moisture at harvest.

The treatment yields do not provide a clear take-home message of the results, except perhaps to show that the highest seeding rate (15 lbs/acre) is not an optimum seeding rate. However, if the 9-lb treatment was ignored, there would be a trend for yield to decrease as the seeding rate increased. A possible explanation for the high yield of the 9-lb treatment is that there were three of these plots proximal to the sub-irrigation ditches, which were exterior to the experiment on both sides. The 9-lb treatment may have been inadvertently favored with better moisture conditions as a result of the experimental design. In hindsight, the experiment should have been blocked across the rows instead of down the rows to account for these field conditions which may have introduced variability in soil moisture. Blocking down the rows accounted for very little unexplained variability, and in future years, the experiment will be designed to account for the variability across the rows.

In summary, it is important to study sorghum cultural practices in the Sacramento-San Joaquin Delta region because crop acreage appears to be increasing, and the Delta is a unique growing region of California. Sorghum seeding rates as a function of plant population were studied to assist growers with determining optimum rates for the Delta environment. While results are somewhat inconclusive, there appears to be a trend for the lower seeding rates to yield the highest. If this trend is shown in future years, then Delta growers could have higher productivity with lower seed costs.

UC Cooperative Extension will host the SJC and Delta Field Crops Meeting on Friday, January 6, 2017 from 8:00am to 12:00pm. The meeting location is the Cabral Agricultural Center in Stockton (2101 E.Earhart Ave., Stockton, CA 95206). 

The agenda is as follows:

8:00am     Doors Open, Sign In, and Welcome

8:10am     Sorghum Seeding Rates for Optimum Productivity, Michelle Leinfelder-Miles, UCCE, San Joaquin/Delta Counties

8:35m       New Pest Advisory: Sugarcane Aphid in California Sorghum, Larry Godfrey, UC Davis

9:05am     The Do's and Don'ts of Planting Grain and Forage Sorghum – Why Sorghum is not Corn!, Jeff Dahlberg, UC Kearney Research and Education Center, Parlier

9:30am      Update on New Herbicide Options for Established Alfalfa, Mick Canevari, UCCE, San Joaquin County

10:00am    BREAK

10:10am    Tools for Selecting Small Grain Varieties from UCCE Statewide Trials, Mark Lundy, UC Davis

10:35am    Comparing Methods for Estimating Crop Consumptive Water Use in the Delta: Background and Preliminary Results, Kyaw Tha Paw U, Eric Kent, Jenae' Clay, UC Davis

11:00am    Nitrogen Mineralization in Soils from the Delta and the Valley, Daniel Geisseler, UC Davis

11:25am    Managing Gophers in Alfalfa Fields, Roger Baldwin, UC Davis

11:55am    Wrap-up and evaluations

Continuing education (DPR and CCA) will be available. Our programs are open to all potential participants. If you require special accommodations, please contact UCCE San Joaquin County at 209-953-6100. Thank you, and hope to see you at the meeting.

Table 1 shows the results of the 2016 UCCE Delta field corn variety trial, located on Tyler Island. Three replicate blocks of eighteen varieties were planted on April 27^th by air planter. The eighteen varieties included 16 varieties submitted by seed companies and two varieties submitted by the grower. All varieties supplied by the seed companies were glyphosate-tolerant varieties. Each plot consisted of four 30-inch beds on an average row length of 1158 feet. Seed was planted approximately two inches deep and six inches apart down the row. The soil is a Rindge mucky silt loam with approximately 20 percent organic matter in the top 15 inches of soil. The Rindge series is a mucky peat soil down to about 60 inches, and approximately 55,600 acres in the Delta are described by the Rindge classification. The previous crop in the field was wheat. Subsurface irrigation by “spud ditch” was employed three times. Nitrogen was applied preplant (125 units/acre as NH₃), and 34 gallons/acre of 8-24-6 with ½% of zinc was knifed in at planting. Weed control was by cultivation and herbicide application (Steadfast, Shark, and No Foam A adjuvant). Zeal miticide was applied. The field was harvested on October 10^th.

The table presents mean values for the three replicates. When interpreting the results, keep the following in mind. The mean is equal to the sum of values divided by the number of values, in this case, three replicates. The statistical method used to compare the means, called Tukey's range test, compares all means against each other. 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”. Seven varieties have a letter “a” following their mean yield, which means that those seven varieties all performed similarly in the trial. The numerical values of these seven varieties differ, but based on this research, we cannot attribute those numerical differences to variety differences. Among varieties, there were also differences in stand count, bloom date, fusarium ear rot presence, 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 some measures, particularly the disease percentage, the variability between the three replicates was very high.

Special thanks go to grower cooperators, Steve and Gary Mello, and participating seed companies. The report is available in an easy-to-print version from my website.