Considerations for choosing the right medium grain rice variety

                        With planting season coming up, thinking about appropriate variety selection is key, and one of the first steps towards ensuring a good 2021 crop. Each year the California Rice Research Board funds a statewide variety trial testing program. Here I summarize some of that data.

These trails are on grower managed fields in eight locations around the Sacramento Valley as seen in the map. One major difference in the locations selected is nighttime temperatures in mid to late July when most of the rice is booting. Cold temperatures during this period can cause blanking and lower yields. On the map, locations in red are where cold nighttime temperatures are usually not a problem. These locations are generally north of highway 20. In yellow are locations where growers need to be concerned about low nighttime temperatures; while they may not occur every year, they are common. In blue (South Yolo) is a location where cold temperatures occur almost every year. Importantly, in each of these regions may be micro-climates where temperatures vary from the “average”.

Some varieties are more tolerant of cold than others. Therefore, it is important to select varieties that are suitable for the location you are farming. In the tables below, are yield data from the past five years for each location in the variety trial. Only the main medium grains varieties are shown (M-105, M-206, M-209, M-210 and M-211). This data will allow for a more informed decision when it comes to variety selection.

The warmer locations are north of Hwy 20,in Glenn, Butte and Colusa counties. At these locations, M-211 consistently outperforms the other medium grains by 4 cwt/ac, on average, over the five years and four locations. Among the other varieties shown, there were no consistent differences among them.

In the cooler locations, M-209 performed the worst in general. In the moderately cool locations (yellow dots on the map), M-105 and M-211 both did consistently well. In the coldest location (South Yolo), M 105 performed the best; while M-209 and M-211 performed poorly. Both M-209 and M-211 have similar days to maturity (about 5-7 days later than M-206). This data suggest that M-211 may have a broader adaptability range than M-209 becasue it appears to be slightly more cold tolerant. However, in the coolest location even M-211 did not perform well.

M-206 versus M-210: M-206 has beenthe most broadly adaptable variety available. While it may not always be the highest yielder, it generally does well across all locations. M-210 is a new variety which has blast resistance. It is basically M-206 with genes for blast resistance and has similar time to heading. Based on these data M-206 and M-210 have almost identical yields in both the warm and cooler regions.

Thoughts on M-211: As seen in the data provided, M-211 is a tremendously promising variety in terms of yield potential. Furthermore, its sensory qualities are similar to premium grain varieties such as M-401. However, one draw back is that for good milling quality, M-211 needs to be harvested at 20-22% moisture. Harvesting below this moisture can result in low milling quality. Given this, it may not be a variety that is suitable for large acreage planting and this should be tested by growers.

I have heard that there may be a shortage of aqua-ammonia (aqua) fertilizer for the start of this year's rice season. This begs the question as to what are the options. In previous studies, we have compared aqua to urea fertilizer. In one study, we compared aqua to liquid urea; and in another study we compared aqua to granular urea. The liquid urea was applied exactly as one would apply aqua (injected 3 to 4 inches below the soil surface). The granular urea was applied to the soil surface, but then lightly incorporated. How much you incorporate depends on the state of the seedbed. If you have a cloddy seedbed, a lot of the urea will fall into the cracks between the clods and relatively little is needed (maybe a light harrow in front of a roller). If you have a fine seedbed it may require a light disking. Importantly (and good news), is that urea dissolves relatively quickly and the flood water also helps move the dissolved urea further down the soil profile (this is not the case with ammonium sulfate). In both studies, we found that urea performed similar to aqua (in terms of yield and N uptake efficiency). However to get these results, you must make sure that the urea is applied to a dry soil before flooding and it be managed so that it gets incorporated below the soil surface before planting (or banded as you do with aqua). I have found that when urea is used, that the crop never seems as uniform as when aqua is used as the main N source; however this has not affected rice yields. It may affect your ability to assess the crop mid-season for an N deficiency.

If you flood the field before applying your nitrogen fertilizer, then have to apply all of your fertilizer N into a flooded rice field. In this case, your N use efficiency will be less and the cost of application will be higher. If you are in this position, apply N in four split applications. Apply 20, 30, 30 and 20% of the N rate at around 2, 4, 6 and 8 weeks after planting, respectively. The first N application should be ammonium sulfate or a starter blend of fertilizer (one that contains N, P and K). We do not recommend urea for the first N application. The other three applications could be urea. Efficiency will be lower in this system, so you may need to increase your overall N rate.

As you know, we have been monitoring armyworm flights with pheromone traps across the valley since 2018. This year, the first set of traps were put out on 4/10 near Princeton, and today we put out a few more. We checked the first traps today, and we got an average of 2 moths per night per trap. That is high for this time of year; in 2018 and 2019 we were not catching any moths until the first week of May. We will start updating our website, UC Rice Online, once a few more traps are established. Remember you can subscribe to receive email alerts every time the numbers are updated on the website.