May05

IRRI agronomy challenge: combine harvest—what a mess to deal with

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

2 May

We have managed to quickly harvest our crop today before total disaster could strike. The last few days have been a rollercoaster ride. I was traveling when I received a cryptic message from Leigh saying that we had 70% lodging in the field.

Achim Dobermann and Leigh Vial harvest their crop.

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When I returned and visited the field yesterday it was over 90% lodged, and occasional rains were still happening. So, we were facing a serious problem of a lodged crop that was mature but quite wet, and could easily rot, shatter grain or even have seeds germinate if we wouldn’t move fast.

We went in with one of IRRI’s Thai combine harvesters today and it wasn’t easy to pull the lodged plants in, but it worked. Sure enough, half an hour after we were finished we had another rain shower.

It’s been well over 25 years since I drove a combine harvester, back in Germany, and that was certainly not a rice combine. I had a bit of initial trouble getting used to it, but managed to complete a full round. Not easy, considering the state the crop was in. Had to cut very very low and go very very slow. Great fun nevertheless, after all that hassle we had with growing our crop.

How did we do? We harvested a total amount of 1427 kg rice (paddy) at 21% moisture, which equals 1310 kg grain at 14% moisture and thus translates into a grain yield of 5.24 tons per hectare. That’s about 1 t/ha more than the average rice yield in the Philippines, but also nearly 1.8 t/ha less than what we had set as our own goal to achieve.

We assessed the harvest losses by estimating the density of dropped grains in the field. Where the crop was harvested the ‘right’ way – with the crop lying away from the combine – we lost an estimated 0.63 t/ha, or 11% of the total yield. Almost all of the losses were from grains shedding from the panicle and dropping to the ground before being fed into the header. Where it was harvested the ‘wrong’ way - that one challenging strip I braved where the crop was facing towards the combine – we lost an estimated 2.4 t/ha, or 41%. Ouch! 2-4% loss is generally regarded as normal, and 10% is not unusual for lodged rice. If the reel was slower, it could have gathered the crop more gently and losses would have been lower, but at least the field is finished, as further rain falls each day.

Why did we get that sudden lodging? It wasn’t too much nitrogen fertilizer, but probably a combination variety choice, crop establishment method and weather. We noticed that throughout the IRRI Farm this particular variety, NSIC Rc 222, was lodging in many trials in this growing season. Moreover, because of the broadcast sowing the plants weren’t as deeply anchored in the soil as in transplanted rice. The late rains in recent days didn’t do any good either.

I was shocked yesterday, but I’m a lot more relieved today. We'll analyze our yield gap soon in more detail and we’ll also figure out whether we made a profit or not. Overall and given the numerous challenges we faced during the whole season, I’d say it wasn’t a total disaster. We certainly learned a lot towards doing better next time, and with a bit more luck it could have been the 7 t/ha we had hoped for. Yet, luck is not something one can rely on very often.

It’s time to start thinking about what to do next, towards preparing for the next cropping season. That’s the blessing in disguise in the humid tropics.

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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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