Most of the rice plants under our center pivot in South Africa are starting to head with some panicles in the milk stage. People often ask me how’s your rice doing under the pivot. Without meaning to dodge their question, my usual reply is, “well, it depends on which part of the field you are talking about.” Thankfully, there are some places in the field that will make satifactory rice yields. See photo on right for good area. There are definitely good and bad areas and my quest now is to determine why the bad areas are that way. Some of the reasons are obvious. For example, our experiment has designed to include low irrigation water treatments causing the plants to stress in those zones. It does not make the field look “pretty” but it will provide important data that we need to understand rice water use. Also, on the far north side, from the beginning, we had a very poor stand because of trash (leaves and stems) in the Nerica seed which clogged the drill at planting. At first, the planter driver stopped every few meters to clean out the stopped up drills but after several hours of doing this it was decided to keep going and hope for the best. Unfortunately, where there is not a good stand of rice, weeds and grass will always fill in the gaps. Another early season problem that we had was glyphosate resistant volunteer maize. It was the thickest stand of volunteer maize in a field that I have ever seen. But, most of that is gone now thanks to Clincher herbicide and slashing.
We finally have the beetles under control after two insecticide sprays. The last chemical sprayed was AviGard, mercaptotion (250ml per 100 liters water). It took about 18 hrs to work but most of the beetles eventually died except the ones in the photo on the right that were mating.
One of my concerns with this rice crop is plant height variability (“waveness” across the field) and yellow plant color in some areas. Usually, fertigation helps correct this problem. To help diagnosis the problem, we collected tissue samples from “good’ and “bad” areas of the field.
The results of the tissue test are shown above. In case, it’s too small to read- main differences are Good rice: 4.0% N, 0.23%S, and 500.6 mg Mn/kg; Bad rice: 2.98%N, 0.15%S, and 258.8 mg Mn/kg. It is late to try and correct the low N, S, and Mn but we can use this for planning next year’s fertility program. What I do not know is whether the low tissue levels in the “Bad” rice was caused by low soil fertility levels or an indirect effect from herbicide injury. Yesterday, I noticed a interesting part of the field. The rice in this area is over waist high and has large panicles.
In the photo on the right, look at the taller rice in the center background. I plan to take soil samples from this area and compare it to a “bad” area to see if there is an obvious fertility difference that we need to address in next year’s fertilizer program.
The photo to the left shows a closer look at the tall rice.