IRRI Agronomy Challenge 2: The end is near

Author // Dr. Achim Dobermann Categories // Achim Dobermann's blog

22 March

As I’m sitting here writing this blog, a heavy rain is pouring down. Yesterday, when we were out in the field, I was reflecting on how nice the weather had been in this growing season, with more sunshine and perhaps a higher yield potential than last year. That is what I wanted to write about, but now I’m reminded again that, although the end is near, nothing is certain yet. Last year, we had heavy rains just a few days before the crop was mature, resulting in nearly complete lodging and severe harvest losses. So, anything can still happen and I had better hold back from making any optimistic predictions.

Achim and Leigh discuss whether or not they had applied enough nitrogen fertilizer. 

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So, what did we talk about yesterday in the field? Well, one thing we were arguing about is whether we had applied enough nitrogen or not. Leigh thinks it wasn’t enough, whereas I think it was (120 kg/ha on the inbred vs 150 kg N/ha on the hybrid), at least for the yield we’re going to get. Looking at the crop, I am still convinced of that because, even now, just a couple of weeks before maturity, the upper leaves are nicely green and grain filling along the entire panicle appears to be good. There is, of course, the possibility that I’m biased in that judgment by looking at only a few places, whereas there are other areas in the field where the crop stand is poorer and some more nitrogen might have helped.

Achim Dobermann and Leigh Vial examine the grains of the rice plantsAchim and Leigh examine the grains of the rice plants.

The other problem we’re facing now is making a decision on when to harvest. As expected, the hybrid is well ahead and will probably reach physiological maturity in 7–10 days, and should thus be harvested around April 5. Physiological maturity is the point at which grain filling effectively ends and it typically occurs several days before harvestable maturity. Harvestable maturity is determined by grain moisture, which is generally 18–23% at the time of harvest. The inbred will take at least 1 week longer to mature. So, in order to avoid unnecessary losses, we probably have to harvest them separately, according to their maturity. It’ll be a democratic choice: one for Leigh and one for me to harvest.

I’m interested in learning more about this crop in terms of its yield components so that we can understand better what may have caused the yield we will harvest. So, if time allows, I would like to do a more detailed assessment of that just around physiological maturity. We’ll put on a final small irrigation to finish the crop, but then drain the field so that it becomes dry enough in time for the combine harvest.

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About the Author

Dr. Achim Dobermann

Dr. Achim Dobermann

Achim is a soil scientist and agronomist with 25 years experience working in Asia, North America and Europe. He is recognized internationally as an authority on science and technology for food security and sustainable management of the world's major cereal cropping systems. He has authored or co-authored over 250 scientific papers and two books on nutrients in rice and has received numerous awards from various academic, government and industry organizations. He is a Fellow of the American Society of Agronomy and a Fellow of the Soil Science Society of America.

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