Louisiana Rice: Planting Stalls In The Rain

Click image to enlarge. Cold damage in rice. Photo: Louisiana State University.

Rice planting has slowed somewhat in southwest Louisiana over the last couple of weeks due to the rains we received last week. However, water seeding acres picked up as the rain drained from fields last week.

This week we have had a short window, from Tuesday (March 22) to Thursday morning (March 24) where we were able to get in the fields at the Rice Station in Crowley to drill-seed some research trials. But a bit further west, less rain was received and some farmers were able to continue drill-seeding last week.

Only a limited number of acres are planted so far in central Louisiana, and no planted rice acres have been reported to me from northeast Louisiana so far. This is to be expected since a lot of the area is still dealing with the excessive rain fall total from a week earlier.

A large band of storms is passing through Louisiana this morning (March 24) as I write this newsletter. Hopefully, the rainfall totals will not be too high and cause additional flooding. If I were to estimate the rice acres in the state today, I would guess that we are probably around 40% to 45% planted in the state, with almost all of the planted acres currently south of Alexandria.

Click image to enlarge. Cold damage in rice. Photo: Louisiana State University.

Click image to enlarge. Cold damage in rice. Photo: Louisiana State University.

Cold Damage In Rice – What It Looks Like

Click image to enlarge. Cold damage in rice. Photo: Louisiana State University.

Click image to enlarge. Cold damage in rice. Photo: Louisiana State University.

We did see some cold weather earlier this week. Here in Crowley it actually dipped down to 37oF on Monday (March 21). Cold weather can affect rice development at the seedling stages.

Seedling cold damage often causes seedlings to turn yellow or it can also cause a yellow or white band across the leaves. The white band is generally a combination of wind and cold temperature damage of the seedling at the soil line.

As the seedling recovers, the white band becomes more prominent. Normally seedlings grow out of this damage as temperatures increase.

Occasionally, frost will kill rice down to the soil level. The good news is that seedlings will normally recover from this type of damage by continued leaf growth from below the soil surface.

So, if you see the white band on your rice this week that looks similar to the pictures in this newsletter, then it is most likely due to the low temperatures that were observed earlier this week and not herbicide damage or another disease.

Sulfur and Zinc Fertilizer Sources for Rice

Sulfur and zinc are important plant essential nutrients needed for rice development. A soil test is very good at determining if sulfur or zinc is limiting in your soil and if you need to apply additional sulfur or zinc to maximize rice yields. However, the fertilizer source is important to both these fertilizer nutrients to be adequately utilized in rice.

Sulfur must be in the sulfate form (SO4-2) to be utilized by plants. Ammonium sulfate, zinc sulfate, and other sulfate fertilizers are excellent sources of sulfur. Elemental sulfur (S2) fertilizer (commonly 0-0-0-90 S) is not a good fertilizer source to use in-season for rice because the sulfur is not in an immediately available form.

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The elemental sulfur must be converted to the sulfate form before it can be made available for rice. This conversion is called sulfur oxidation and it is done by sulfur oxidizing bacteria. Most of the sulfur oxidizing bacteria require…drum roll please… you guessed it, oxygen.

Once the rice is flooded, generally very little elemental sulfur will be converted into sulfate sulfur. In upland conditions, elemental sulfur oxidation to sulfate sulfur is a slow process that can be influenced by several factors including the size of the fertilizer (powdered will be oxidized faster), temperature, soil pH, soil water content, oxygen availability, and the amount of sulfur oxidizing bacteria in the soil.

In upland conditions, large granule of elemental sulfur, like the one shown in in the picture, will be very slow. For example, one study illustrated that for a granular size similar to the one in the picture only 2% of the elemental sulfur would be converted in a one month period of time.

Therefore, applications of elemental sulfur for rice in-season for a soil that is deficient in sulfur is not recommended. However, applications of elemental sulfur are recommended in the fall and winter to bring soil test sulfur levels up and also to help lower soil pH.

Similarly, zinc must be in a soluble form to be utilized by rice immediately. Generally, we would like to see producers use zinc fertilizer sources that are at least 50% water soluble. Less soluble forms, like zinc oxide, are not immediately available and are not recommended for rice grown in a soil that is limiting in zinc during the growing season. The water solubility of zinc fertilizers is stated on fertilizer labels.

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