IRRI Agronomy Challenge 2: Crop assessment

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

31 January

It’s 40 days after planting, so time to judge how well the vegetative growth has been. We’re at the end of tillering stage, close to panicle initiation. What do we see? Well, there is a visible difference between the one half of the field that was planted with the hybrid, and the half that was planted with an elite inbred variety.

The hybrid plants are taller and they look more vigorous, with stronger stems. It’s expected to see hybrid vigor, but some of that may also be because of the 1 week shorter growth duration of the hybrid chosen, compared to the inbred. It also seems that in the hybrid half we have less skips and patches with no or poorer growth.

We knew that with the mechanical planter such patches can happen when the planting mechanism fails to grab seedlings or when the tiny seedling disappear in deep, muddy soil. Somehow there seems to be less of that in the hybrid half, or the hybrid seedlings recovered more quickly. We’ll see how this all pans out in terms of yield, but so far it’s an interesting observation.

Overall, I’d rate the crop stand uniformity as a B-.

Can we judge what yield we’ll get? No, way too early for that. One thing is clear: compared to the broadcast-sown crop we grew last year our yield components will be entirely different. In broadcast seeding you typically have many plants per square meter, but each has only few tillers (and thus few panicles per plant) and individual panicles tend to be relatively small. In our mechanically planted crop with 30 cm row spacing we’ll end up with fewer plants per square meter, but many more tillers (and panicles) per plant and probably also larger panicles.

Achim Dobermann (rt) and Leigh Vial (lt) assess their rice plants

Achim (rt) and Leigh (lt) assess their rice plants.

We’re also learning some new lessons from others. Not far away, in another study, IRRI researchers have machine-planted some plots without any prior tillage, i.e., as no-till mechanical transplanting, directly into wet soil. That’s something that has been pioneered in recent years in some parts of India with good success - see the video. It saves a lot of energy, water, time and labor needed for land preparation, so maybe this is another promising way forward for certain locations and growing seasons. However, it may have also have some other drawbacks that require more study.Without the usual plowing and puddling there may not be a good plowpan, thus resulting in higher water percolation rates and more frequent need for irrigation. Everything has its tradeoffs in life, I guess.

On the bright side, compared to last year, we didn’t have any major crop damage due to birds eating the seed, snails or rats. Weeds are also less of a problem. We only did one pre-emergence herbicide application, which has provided pretty good control. We spotted a few weedy patches today, probably where the herbicide application done with a backpack sprayer wasn’t uniform enough.


  • Hire a couple of contract laborers for doing spot hand-weeding later today.
  • Drain off the water to have a good mid-season drainage for about 3-4 days. That’ll bring in oxygen and dry the soil surface before applying the next dose of nitrogen fertilizer.
  • Apply 45 kg nitrogen per hectare at panicle initiation, as per Nutrient Manager recommendation.
  • Re-irrigate.
  • Next week take a look at our crop health situation. So far, we haven’t sprayed any insecticide or fungicide yet. Will we need anything?

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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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