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 discuss, among other things, whether or not they had applied enough nitrogen fertilizer.
Commentary from Achim:
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 better hold back with making any optimistic predictions.
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.
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 about 7-10 days, and should thus be harvested around April 5. Physiological maturity (PM) is the point at which grain filling effectively ends and it typically occurs several days before harvestable maturity. Harvestable maturity (HM) is determined by grain moisture, which is generally from 18-23% at the time of harvest. The inbred will take at least one 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 like to do a more detailed assessment of that just around physiological maturity stage. We'll put on a final small irrigation to finish the crop, but then drain off the field so that it becomes dry enough in time for combine harvest.
International Rice Research Institute
4 years, 6 months ago