- Author: Bruce Linquist
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.
We have gotten several calls about the use of zinc (Zn) fertilizers to address potential Zn deficiencies. The price of zinc is going up, and it is prompting growers to look more carefully at the use of zinc. Use of zinc fertilizers became widespread in the late 1970s after it was discovered that the “alkali disease syndrome” was caused by zinc deficiency. The problem was widespread in the Sacramento and San Joaquin Valleys and affected young seedlings after the first true leave emerged. The syndrome consisted of yellowing of leaves from the base up, weak leaves that floated in the water, and plants eventually dying 4 to 6 weeks after seeding, resulting in thin stands. Cool temperatures during the early part of the season can exacerbate zinc deficiency problems.
Currently, we do not know how widespread zinc deficiency is. We know that zinc deficiency is more common in alkaline soils (pH higher than 7). In such soils a level below 0.5 to 0.8ppm (obtained by theDTPA method) suggests a deficiency. In soils with pH lower than 7, the threshold for zinc deficiency is 0.3ppm. Duringtillering stage, a Y-leaf Zn concentration of
Based on research out of the 70s, you can correct for Zn in a couple of ways. First by applying a Zn fertilizer. This is most often done by adding some Zn containing fertilizer (e.g. zinc sulfate, chloride, or nitrate) to the starter fertilizer blend. In most fields, no more than 8 lbs of Zn/ac was needed to correct deficiencies. Another option is to coat the seed with Zn before planting. When coating seed, 2 lb of Zn per 100 lb of seed was enough.
If you are reassessing the need to use Zn, use the pH and Zn content of your soil to decide if the investment in Zn is justified. Also, if you are using a starter fertilizer that has Zn in it, you may be supplying enough to address any deficiency.
Field with suspected zinc deficiency./table>
- Author: Michelle Leinfelder-Miles
Weeds are important pests of California rice systems, and weed management can account for roughly 17 percent of total operating costs, according to a UC cost of production study. Integrated weed management uses cultural and chemical practices and considers the following:
- Prevention (e.g. using certified seed, equipment sanitation, maintaining roads and levees)
- Cultural practices (e.g. land leveling, crop rotation, tillage, winter flooding, drill-seeding)
- Fertilizer placement and management
- Water management
Herbicides are important tools; however, resistance can occur when products are not rotated, or when diverse chemistries are not available.
In 2019, in cooperation with Corteva Agriscience, I conducted a trial to evaluate the efficacy of a new herbicide product called Loyant (florpyrauxifen-benzyl). Loyant is registered in rice growing states in the southern US but would be a new chemistry in California. Corteva Agriscience anticipates California rice registration in 2020, with the product being available for use in 2021. Previous trials have shown that Loyant provides good control of broadleaf weeds (e.g. ducksalad, redstems), smallflower umbrella sedge, and ricefield bulrush. It has some activity on Echinochloa species (e.g. barnyardgrass, watergrass). More data was needed, however, in drill-seeded systems. The objective of the trial was to assess the efficacy and crop tolerance of Loyant for weed control in drill-seeded rice in California.
The trial took place in the Delta region on a Kingile muck soil. This soil classification is characterized as having upwards of 40 percent organic matter in the top foot of soil. On high organic matter soils in the Delta, the typical practice is drill-seeding. Water-seeding is not successful in the Delta because the soil particles can float and move too easily, causing seed to get buried too deeply and germinate poorly.
For a full report on this trial with methods and crop injury data tables, please see my website. Treatments are described in Table 1 below. We observed slight to noticeable leaf curling in the Loyant treatments at 14 days after treatment (DAT), but this had disappeared by 21 DAT. We observed no stunting or stand reduction with any of the treatments; nor did we observe any differences in heading. All treatments had similar weed control with the exception of the Prowl-only treatment, which had statistically higher weed counts. Loyant does not control sprangletop, so sprangletop was the weed most commonly observed. We found no differences in yield or seed moisture at harvest (Table 2 below), and we observed no lodging. Yield averaged 8965 pounds per acre across treatments, and seed moisture averaged 13.7 percent.
In summary, the purpose of this trial was to learn the efficacy and crop tolerance of Loyant (florpyrauxifen-benzyl) for weed control in drill-seeded rice. We observed slight leaf rolling with the Loyant treatments a couple weeks after treatment, but those symptoms were gone by the third week after treatment. We observed Loyant to have good activity on the Echinochloa species but not on sprangletop, which was expected based on previous company trials. We observed Loyant treatments to have similarly low weed counts compared to the grower standard practice, and no significant differences in yield among the treatments. Tank mixes will be needed to manage sprangletop. The results indicate that Loyant could be used in drill-seeded rice herbicide programs, providing a different chemistry for herbicide resistance management.
This information on products and practices is for educational purposes only and does not constitute an endorsement or recommendation by the University of California.
Table 1. Rice herbicide treatments.
Table 2. Rice herbicide trial yield results.
- Author: Bruce Linquist
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/.
- Author: Ian Grettenberger
- Author: Luis Espino
Want to help make sure your freshly planted rice fields don't look like the muddied mess on the left below (vs. clear on right) following a pyrethroid application? Wondering if your tadpole shrimp are becoming less susceptible to pyrethroids? We do too! Pyrethroids are widely used for managing resistance and resistance seems to be a growing issue.
We are looking for additional fields where we can sample tadpole shrimp to test for pyrethroid resistance. We will be gathering soil/shrimp and then using these samples to run laboratory bioassays and measure susceptibility. The goal is to start measuring precisely how susceptible populations are in different fields. This will help us determine precisely how resistant known resistant populations are, how prevalent low levels of resistance are, and how “susceptible” currently susceptible populations are to generate baseline data. This will help generate the long-term baseline data we need to stay on top of this issue. We will anonymize any publicly available data. In addition, we hope that by measuring resistance in individual fields, we can help you by noting any susceptibility slippage that may not have shown up yet in terms of control. We can also help address questions about whether lack of control is due to resistance or application issues.
Types of fields:
- Fields with known resistance to pyrethroids in tadpole shrimp (control issues).
- Suspect fields where you think resistance is an issue, but it is a just a hunch or a concern.
- Any other field. Even if pyrethroids have been working well, it is still good to know susceptibility levels and for us to generate baseline data.
What we need:
- Access to field(s)
- Summary of your ability to manage tadpole shrimp with pyrethroids, any declines in susceptibility, etc.
If you are interested please email or call (Ian) at email@example.com or 530-752-0473.