Achim Dobermann, deputy director general for research at the International Rice Research Institute (IRRI; http://irri.org), and Leigh Vial, head of IRRI's experiment station, begin IRRI Agronomy Challenge II. It is the continuation of a special project in which they demonstrate how to grow a productive rice crop in a 25 x 100-meter field on IRRI's research farm.
In this installment, Achim and Leigh assess the crop at 40 days. Also joining the discussion is IRRI postdoctoral James Quilty.
Commentary from Achim:
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.
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. 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.
• 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?
International Rice Research Institute
6 years, 3 months ago