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Contact Information:
Contact Dr. Tao via email at haiying.tao@wsu.edu or via phone at 509-335-4389.
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Episode Transcription:
[ Music ]
Drew Lyon: Hello. Welcome to the WSU Wheat Beat podcast. I’m your host, Drew Lyon, and I want to thank you for joining me as we explore the world of small grains production and research at Washington State University. In each episode, I speak with researchers WSU and the USDA-ARS to provide you with insights into the latest research on wheat and barley production. If you enjoy the WSU Wheat Beat podcast do us a favor and subscribe on iTunes or your favorite podcasting app and leave us a review while you’re there so others can find the show too
[ Music ]
Drew Lyon: My guest today is Haiying Tao. Dr. Tao is an assistant professor in soil fertility and nutrient management in the department of crop and soil sciences. Haiying was born and grew up in inner Mongolia, northeast of China. She came to the US in 2002 and obtained her Ph.D. degree in soil fertility at the University of Connecticut in 2007. She worked on two large multi-state projects in nitrogen loss reduction and land application of livestock manure prior to joining WSU. She joined WSU in August 2015. Her research and extent in focus at WSU is soil fertility and soil health management for dryland cropping systems. Hello Haiying.
Dr. Haiying Tao: Hello Drew.
Drew Lyon: So, how will nitrogen deficiency result in yield lost in canola?
Dr. Haiying Tao: Right. Nitrogen is very important for winter canola yield. Nitrogen fertilizer applications in nitrogen deficient soils can increase overall plant growth. Specifically, plant is taller and the plant stem is larger and stronger so leaf area and leaf duration increase. Number of branches and number of flowers on each branch increase as you provide better nitrogen availability. A number of parts and weight of parts will also increase. All this are important for yield.
Drew Lyon: How much nitrogen does winter canola need?
Dr. Haiying Tao: For winter canola, there are two rapid nitrogen uptake stages. So, the first rapid nitrogen uptake stage is during fall growth and the second is from spring grain up to flowering. It depends on the environmental conditions. Substantial amount of nitrogen can be also taken up after flowering and even at grain filling stage. But in dryland Washington state, most of nitrogen is taken up before flowering.
Drew Lyon: Okay.
Dr. Haiying Tao: So during fall, winter canola can accumulate anywhere from 30 to 130 pounds per acre of nitrogen. That really depending on the planting date, the growing degree days, and moisture. So over the winter, about one-third of that accumulated nitrogen can be returned to the soil through leatflet.
Drew Lyon: Oh, okay. So, the leaves that fall off during the winter just cycle the nitrogen back into the —
Dr. Haiying Tao: Cycle them back. Right. And then total nitrogen uptake also depends on yield and your nitrogen management practices. So, it could be from less than 100 pounds per acre to more than 300 pounds per acre total nitrogen uptake. This wide range does not seem help but farmers can estimate total nitrogen uptake easily using their yield, seed protein, and nitrogen harvest index. So, our research shows that winter canola seed protein concentration is anywhere between 18 to 30%. It really depends on, again, your nitrogen management practices. And we also know that in the protein, 17.5% of it is nitrogen. So, to estimate a total nitrogen uptake, you can first estimate how much nitrogen is in the seed. So, you can make this calculation using yield times protein concentration times the 17.5%. So, we also found that winter canola grown in Washington State has nitrogen harvest index of 65 to 85%. So, use amount of a nitrogen in seed. We just talked about how to calculate it, divided by nitrogen harvest index, you come up with the total nitrogen uptake.
Drew Lyon: Okay.
Dr. Haiying Tao: So now, you may want to ask what is nitrogen harvest index?
Drew Lyon: [ Laughter ] Yes. That was going to be my next question.
Dr. Haiying Tao: So that is nitrogen in seed divided by nitrogen total uptake which is total aboveground nitrogen. So basically, nitrogen harvest index is a percent of nitrogen taken up by the crop that ends up in the seed.
Drew Lyon: And this was at 65 to 85 —
Both: To 85%.
Drew Lyon: And how does a grower decide which number to use when making the calculation?
Dr. Haiying Tao: Right. That’s a good question. So, this really depends on many factors. So, I think farmers if they want to use exactly how much what the nitrogen harvest index is, they have to actually cut a little bit in their field and make this calculation. But overall, I think to estimate, make an estimation they could use the range or just average.
Drew Lyon: Okay. Use 75% of if they have some reason to believe it’s not that good this year go down to 65 or if they think it’s really good use the 85.
Dr. Haiying Tao: Right. Exactly. And it’s heavily affected by the rainfall.
Drew Lyon: So, a high rainfall year would tend to have a higher nitrogen uptake and a lower rainfall year less or?
Dr. Haiying Tao: Right. Right. So, if you — so the nitrogen, how much nitrogen ends up in the seed that is heavily affected by the water availability. So if you have better water availability as nitrogen reallocation stage, then you have more nitrogen can be removed to the seeds. Then your nitrogen harvest index is higher.
Drew Lyon: Okay. So how much nitrogen do you take off when you take the seed off? So, at the harvest time, how much nitrogen are you pulling off in a typical winter of canola crop?
Dr. Haiying Tao: Right. So estimated nitrogen removal by harvest is very important for nitrogen management for the falling crops because by estimating, excuse me, nitrogen removal, we can estimate how much nitrogen is removed from the field and how much nitrogen is left behind in the crop residue. So canola growers know that winter canola is nitrogen scavenger, right? Its deep and expanded root system is capable of taking up nitrogen in deep soils that wheat left behind. So, much of nitrogen taken up by canola is left behind in the field in the crop residue, and when crop residue decomposes, this nitrogen can become available for the following crop. So, although like I just said, is it is hard to say exactly how much nitrogen is removed by harvest, farmers can easily estimate how much nitrogen is removed with harvest. To make this estimation farmers needs to know seed yield and seed protein concentration. And seed yield can be measured using yield monitor, and seed protein concentration can be measured easily using an IR equipment which is how weed protein is measured. So if farmers are familiar with that, then they would know how to measure the protein content in the oil seed as well. So then, like I described earlier, then you can use yield protein content and the nitrogen percentage in the protein and to estimate how much nitrogen is removed with harvest. For example, if you have a field that yields 1,000 pounds per acre of seed and the protein content is 20%, so the nitrogen removal with harvest will be 1,000 times 20% times 17.5% which comes up with 35 pounds of nitrogen per acre removal with the seed.
Drew Lyon: Do you have, by any chance, I think we have a calculator on the small grains website, smallgrains.wsu.edu for wheat that lets people do this. Do we have anything similar to that for canola?
Dr. Haiying Tao:That’s very interesting that you ask because I was just thinking about it. I think it would be very useful for farmers to have this calculator. I think we should start working on it.
Drew Lyon: All right. Well, maybe that will happen here. I do think that would simplify the math for everybody, and it sounds like it’s a pretty straightforward mathematical equation.
Dr. Haiying Tao: Yes.
Drew Lyon: So, how do we determine how much nitrogen winter canola needs?
Dr. Haiying Tao: So currently, we use yield goal-based method to estimate nitrogen weight for winter canola. In another word, we estimate nitrogen application rate based on yield goal. Based on our two-year research we recommend approximately five to seven kilogram of nitrogen per acre for each 100 kilogram of seed yield, which we call it unit nitrogen requirements.
Drew Lyon: So, for people out there who might not know what a kilogram is, it’s about 2.2 pounds in every kilogram.
Dr. Haiying Tao: In every kilogram. Right. So, the unit nitrogen requirement is lower in the higher yield zone and vice versa. This is because winter canola that has higher yield potential has better root systems which contribute to greater nitrogen extraction from large volume of soil.
Drew Lyon: Okay.
Dr. Haiying Tao: And this means if your yield potential is high, you use five. If your yield potential is low, you use seven.
Drew Lyon: Okay.
Dr. Haiying Tao: [ Drew laughs ] However, there’s another important thing to consider when you consider nitrogen application rate which is soil test. So, if your soil test in the six-foot, six feet depth is higher than 100 pounds per acre, we do not recommend any nitrogen applications because the research for both winter canola and spring canola conducted in Washington State showed that if you have soil test greater than 100 pounds per acre, than the chance that you get yield benefit from additional nitrogen fertilizer applications is very low.
Drew Lyon: Okay. And you go — I think a lot of people only sampled a three or four foot but because canola has this big extensive root system, you want to take that test to six foot and both for winter canola and spring canola?
Dr. Haiying Tao: Right. So especially for winter canola, we definitely recommend six feet, but for spring canola if there’s any difficulty with deep sampling and four feet.
Drew Lyon: Okay. Good. Is it true that seed oil — so the amount of oil and the amount of protein in the seed are negatively correlated? It seems to me I recall hearing that meal, canola meal is a sought after commodity, but generally if you have high oil content you have lower protein in the meal. Is that true or is that just something that is seen sometimes?
Dr. Haiying Tao: Yes. It’s true, and it’s always.
Drew Lyon: [ Laughs ] It’s always. Okay. You put me in place.
Dr. Haiying Tao: Right. With all the seven sites that were conducted and with other research that was conducted in other areas, all show that seed oil concentration and protein concentration are negatively correlated. That means the higher the protein concentration, the lower the oil content is, right? For example, in the seven sites we conducted, research on nitrogen management we found that in average the oil concentration reduced from 47% to 36% when the protein concentration increased from 17% to 30%. So, this is one of the reasons that we should manage our nitrogen very carefully. If farmers want high oil concentration they should apply nitrogen up to optimum nitrogen rate for maximum yield. But if too much nitrogen is applied, you won’t get yield benefit, but your oil concentration will be reduced.
Drew Lyon: It will be reduced?
Dr. Haiying Tao: It will be reduced. So you do not want to overapply nitrogen, right? But if farmers would like high protein content, which is possible, like you imagine it because protein in the canola meal is also valuable for animal feed, fish meal, and even soil amendment. So in that case, and then if there is a premium for protein and they can consider applying more nitrogen, and I will talk about timing of application also as a factor on the protein content.
Drew Lyon: And what’s that affect?
Dr. Haiying Tao: So, again, we found that, of course, none of our research site needed fertilizer nitrogen when we did our research project which means we could not determine the best nitrogen application timing for yield. But, we found the nitrogen application timing has effect on the protein content and oil content. So, that answers your question. So when nitrogen is applied in fall, you have — so comparing fall applications, spring applications and split between fall and spring applications. So, the fall applications you have highest oil content in the seed, but if you apply all the nitrogen in spring then your oil content is lowest. But if you split nitrogen in fall and spring, it depends on where you are. So, if you are in a low rainfall area or intermediate rainfall area, then the spring application are split between spring and fall, you would end up with a similar amount of oil concentration. But if you are in a high rainfall area, so the split application actually ends up a little higher oil content than spring application. So basically, a spring application will end up with lowest oil content.
Drew Lyon: So, if you’re going for meal high protein you’d want to put it on in the spring, but if you’re going for oil content it’s better to put it on the fall. Is that the general message?
Dr. Haiying Tao: It’s one of the factors that you want to determine where you want to apply for nitrogen because nitrogen use efficiency is also important. Not only important for the environment but also important for farmer’s inputs.
Drew Lyon: Bottomline.
Dr. Haiying Tao: Yes. Their wallet, right? So, if farmers are in high rainfall area and we found that the fall application has the least nitrogen use efficiency. In fact, most of nitrogen is lost during the heavy rainfall winter season.
Drew Lyon: So you’ll leach a lot of that water.
Dr. Haiying Tao: You leach a lot or you have standing water so that you have denitrification. So, especially like if you have to delay your planting date because you don’t have moisture and you don’t plant until late in fall so which means your canola is very small in fall and over winter. So, because your canola is little it does not require that much of nitrogen and the root system is not capable of taking up a lot of nitrogen. So all of the nitrogen that you apply in fall will end up leaving.
Drew Lyon: So, we talked about nitrogen use efficiency in winter canola. What are the most important factors that affect that? Timing must be one of them, right? We just talked about. What else?
Dr. Haiying Tao: So, water. Water is always important. Water is the determined factor for yield and nitrogen use efficiency like we talked about. In higher rainfall zone, if nitrogen is applied at right timing the nitrogen use efficiency can be higher in lower rainfall zone. But, of course, this is because in higher rainfall zones, winter canola has higher yield potential therefore higher nitrogen use efficiency. And nitrogen use efficiency is also affected by nitrogen management, like one of the things we talked about which was the timing, and nitrogen application rate also has a factor on nitrogen use efficiency. So, if you apply more than needed and the more you apply the less of nitrogen use efficiency you would end up with. And there’s another important factor that affects the nitrogen use efficiency that we did not — we haven’t talked about which is form of nitrogen. So, what type of nitrogen the farmers use. And that what is the best form also depends on where you are. Sorry about that.
Drew Lyon: [ Laughter ] Do not give me a straightforward —
Dr. Haiying Tao: I know.
Drew Lyon: I was looking for that simple answer, but it’s a little more complicated as life often is.
Dr. Haiying Tao: Yes. With nitrogen, it’s the most complicated fertilizer and nutrient that farmers are dealing with. They need a lot of it, but it’s just so complicated. So, in high rainfall area, if you have to apply nitrogen in fall. Of course, we don’t recommend, right? So, if you have to apply nitrogen in fall, it’s best that you choose anhydrous ammonia or aqua ammonia because then you lose less.
Drew Lyon: They leach less.
Dr. Haiying Tao: They leach less.
Drew Lyon: And denitrify less too or is it mostly leaching?
Dr. Haiying Tao: So, that, both.
Drew Lyon: Both. Okay.
Dr. Haiying Tao: And that is even if you apply anhydrous or aqua in fall, you still need to think about when you want to put it down. You do not want to put it down when the temperature is still high. So, you want to put it down when temperature is lower than three degrees Celsius.
Drew Lyon:Which would be about 42 degrees Fahrenheit, something in there?
Dr. Haiying Tao: If you say so. [ Both Laugh ] Sorry about that. So, that’s because below that temperature the microbial activity is low. So, the conversion of ammonia to nitrate is low which means you have less of leaching and denitrification loss.
Drew Lyon: Because the ammonium ion is actually positively charged and attaches to the soil colloid better than the nitrate molecule which is negatively charged and tends to be repelled.
Dr. Haiying Tao: You got it.
Drew Lyon: All right.
Dr. Haiying Tao: But that doesn’t mean you are okay, protected from nitrogen loss because early in the spring when temperature warms up and microbial activity dramatically increase as temperature increases. Right? And then if you have a season, a year that happens to have heavy spring rainfall and you could still reach quite amount of nitrogen. So, that’s in the high rainfall area, but if you apply nitrogen in spring, you want to apply fertilizer that is in the form that contains nitrate. So, for example, you UAN you do not want to apply UAN in fall, but in spring, yes. And spring applications should be made early. So, as soon as grain up stage. You do not want to wait until the rain season is over because then your nitrogen will stay just on the surface. And also, it’s best that you apply nitrogen just before rainfall. So, if you know some rain is coming, you may want to run out and apply nitrogen because it requires about a minimum of half inch of rain to push the nitrogen deep in the soil so that the volatilization loss is minimum.
Drew Lyon: Okay. All right. And what about out in the dry areas? We talked about in the high rainfall areas. What’s the best — is there a preferred form out in that environment as well?
Dr. Haiying Tao: Right. So that depends — so if you are in dry area in the grain fallow area, so the common practice is fall application anyways. So, fall anhydrous ammonia is I think is the most common practice. I think because in that area the leaching loss is minimum so volatilization loss becomes more concerning than leaching loss unless you have an abnormal year that you have high rainfall in the winter. So fall application is okay.
Drew Lyon:All right. Well, nitrogen fertilization in winter canola, a very important topic. Not as simple as I might have thought coming into this conversation. I appreciate your time trying to explain the ramifications of different nitrogen types and timings on winter canola fertility. Thanks Haiying.
Dr. Haiying Tao: Thank you, Drew.
[ Music ]
Drew Lyon: Thanks for joining us and listening to the WSU Wheat Beat podcast. If you like what you hear don’t forget to subscribe and leave a review on iTunes or your favorite podcasting app. If you have questions or topics, you’d like to hear on future episodes please email me at drew.lyon — that’s lyon@wsu.edu –(drew.lyon@wsu.edu). You can find us online at smallgrains.wsu.edu and on Facebook and Twitter @WSUSmallGrains. The WSU Wheat Beat podcast is a production of CAHNRS Communications and the College of Agricultural, Human and Natural Resource Sciences at Washington State University. I’m Drew Lyon, we’ll see you next time.