- (Public Value) UCANR: Safeguarding abundant and healthy food for all Californians
Following my blog post about a week ago about using urea or aqua-ammonia (aqua), a number of people have been asking to see the data. The study was conducted in 2017 at the Rice Experiment Station. Aqua and liquid urea were applied at three rates (50, 100 and 150 lb N/ac). Both N fertilizers were injected into the soil at 3 to 4 inches depth. Treatments were replicated three times. Across the N treatments, yields were similar between the aqua and liquid urea treatments. Yields were low, but overall state-wide yields in 2017 were low as well. In other studies (data not shown), we used dry urea banded into dry soil before flooding to the same depth as aqua we saw almost identical yields across seven on-farm studies. Based on these data, liquid or dry urea that is injected or buried into a dry soil before flooding, performs the same as aqua.
This morning I was out with several members of our research team on the northwest side of the valley planting a variety trial. The grower we were working with had just finished planting all of his rice acreage (1200 ac) yesterday (April 30). Pretty amazing how fast the rice is getting in this year. I know the west side is often earlier than the rest of the valley; however, growers around the valley are moving much faster this year. By the end of next week, we will likely have all of our variety trials (we have seven this year) planted. We have accomplished this so early before.
This is a good start to the season! Generally, when we plant early, yields tend to be higher. This is clear from the figure below. This figure shows state-wide yield averages from 1994 to 2019 relative to the date when 50% of the rice acreage had been planted (based on USDA data). One reason for higher yields is that dry springs (which allow for early planting dates), also give growers time to prepare their seedbed exactly how they want to without skipping passes. From the UCCE Rice Yield Contest, we have seen that good and uniform stand establishment is a key for high yields. Realizing, that the yield potential may be higher this year, the N fertilizer requirement may be a bit higher. It will be important to access the crop midseason (around PI) to see if the crop may need more N fertilizer to realize its potential. This can be done with either a Leaf Color Chart or the Green Seeker.
The UCCE Rice Yield Contest (http://rice.ucanr.edu/Rice_Yield_Contest/) will be running again this year and we look forward to your participation and learning more about how to achieve high yields. The 2020 forms will be available soon. You will need to enter the contest by the Annual Rice Field Day in late August.
In the past few weeks, we have been getting updates from some irrigation districts that water allocations have been reduced in some areas. We have provided some information in past years that will still be relevant this year.
During drought years water deliveries are often restricted. If that is the case, then “what is the least amount of water I can grow rice with without hurting yields?”. Based on past studies, the amount of water delivered to rice fields varies widely (i.e. 4 to 7.7 ft). Of this, evapotranspiration (ET) is roughly 34 inches; percolation in most soils is less than 0.3 ft (due to heavy clay soils & impermeable hard pan); seepage ranges from 0-1 ft; and tailwater drainage is 1-4 ft.
- Don't spill. The values above suggest that rice can be grown using roughly 4 ft of water if there is no tailwater drainage. This could even be less depending on the percolation and seepage characteristics of the field. With no-spill practices, yield can be maintained as long as you receive relatively clean water (low salinity) and the soils are not saline.
- Don't drain at the end of the season. Most growers pull their boards at the end of the season to drain the field in preparation for harvest resulting in significant tailwater drainage losses. Instead, growers should attempt to turn off irrigation before needing to drain and allow the water to naturally subside rather than drain the field. Determining when the irrigation water can be turned off depends on how much water is in the field, climate, and soil properties (percolation and seepage). Fields with heavy clay soils can safely have no standing water 21 to 24 days after 50% heading without risking yield loss and grain quality.
- Fallow fields that require more water. If fields need to be fallowed due to limited water availability, fallow fields with high percolation/seepage potential or high salinity (no-spill water management makes salinity problems worse).
- Short duration varieties. Choose shorter duration varieties which reduce the time period the field has to be irrigated. Shortening the period of irrigation can reduce ET by a couple of inches as well as reduce percolation and seepage losses. Rice typically needs to be flooded from planting to reproductive stage 7 (R7, when one kernel on the mainpanicle is yellow; about 3 weeks after heading).
- On average to reach R7, CM-101, M-104 and S-102 require 100 days; M-206 requires 104 days; M-202 and M-205 require 108-112 days; and M-401 requires 128 days.
- Avoid early plantings. Planting early increases water use because it is during a cooler time of the year. Thus, time to canopy closure and the period the crop needs to be irrigated increases along with the increased potential for higher ET and percolation/seepage losses.
- Dry- versus water-seeding. While it may seem counter-intuitive, dry/drill seeding does not necessarily require less water than water-seeding. Dry seeding can use less water if rice seed is planted to moisture which reduces the need to flush the field in order to germinate the seed.
• For more on this topic a video presentation has been prepared and is available at http://ucanr.edu/insights.
During the January UCCE Rice Winter Grower meetings I asked the audience a number of questions related to how they managed rice in 2019 when they planted during or after the mid to late May rains. As you recall, 2019 May rainfall was one of the highest on record with almost 3 inches falling between mid to late May (see Figure below showing average May rainfall from three CIMIS stations (Durham, Colusa and Davis). Thanks to all of you who participated. We had roughly 140 people respond. About 50% of farmers reported planting their last field by May 25; however, almost 40% of respondents said their last rice field was planted after June 1. These June plantings were more common on fields located east of the Sacramento River as most farmers were able to get their fields in earlier on the west side. Over 80% of the respondents said that in fields planted after the rains, yields were down by up to 10 sacks/ac; while 15% said they were the same. Also, about 25% of farmers reported that grain quality was lower in the late planted fields.
The management area that most farmers said was most challenging was land preparation (37%), followed by weed management (23%), stand establishment (13%) and nutrient management (10%). With respect to weeds, 32% said weed control was similar to other years. For farmers reporting that it was more challenging, most reported that grasses (44%) were the most difficult to control, followed by sedges (18%) and broadleaves (6%). About 50% of farmers reported that the efficacy of their herbicides was worse than normal. Both Kassim and Whitney felt that these two results are not surprising. The grass weeds were able to take advantage of the rains and germinate earlier than the rice making them more difficult to control. Furthermore, granular herbicide efficacy may also have been affected by deeper than normal flooding depth (diluting herbicides) at the beginning of the season, if rains came soon after planting.
Many reported land preparation to be very challenging. About one third of farmers reported that in late planted fields they skipped one or more tillage passes; while 12% skipped rolling. About 80% reported applying aqua-ammonia, although 20% of farmers had to apply aqua to wet soil, while 60% applied to dry soil and may have had to do some extra tillage passes to encourage soil drying. That leaves 20% of farmers that used granular fertilizers for their total N requirement. How these fertilizers were applied (before or after planting) was mixed. This is an area that I will be looking at more this year in an effort to develop better strategies to apply granular fertilizer when aqua is not an option.
Finally, and not necessarily related to the wet year, M-206 remained the most popular medium grain variety overall. It was the main variety planted for 48% of respondents and was grown widely in all regions of the Sacramento Valley. M-209 was the second most popular variety and most widely grown on the west side-particularly in Glenn and Colusa counties. The variety M-105 was planted mostly in Butte County where it was the main variety for over 50% of the respondents in that area. Interestingly, M-105 was not planted as much in the southern part of the valley where it yields well and heads relatively early. Talking with some growers, while they like the yields, they feel M-105 may be more prone to lodging than M-206 which delays harvest.
If you missed the rice grower meeting this year, the presentations can be seen at http://rice.ucanr.edu/Presentations/Winter_Grower_Meetings/.