Author: Karen Roberts
Last saved by: Craig Bratby
Company: Department of Primary Industries

How to estimate wheat yields 
     
Paul Parker, District Agronomist, Young and Karen Roberts, District Agronomist, Parkes
YouTube video transcript 10 October 2012

Estimating the yield of crops prior to harvest is a useful skill for a range of reasons from insurance assessments to harvest management. Paul Parker, District Agronomist with NSW DPI (NSW Department of Primary Industries), has been accurately estimating yields in crop judging for the last 38 years as the NSW state crop judge. In this video Paul shares his tips for assessing cereal yields.
Paul: Well firstly I make sure that I do a reasonable walk into an area before I start assessing yield, Karen, because I want to get an idea of the average density of a crop. So I’m starting to look for density, evenness of the crop in terms of its density, how well the grain’s filling, how the heads are filling, the size of heads, and just an overall view of things that might be present, whether weeds or whatever that may impact on that yield as well.
What formula do you use to calculate yield? 
Paul: Once I’ve walked through it, I start to assess what I believe are average areas in the crop, and that’s where Ill start to do a count so I can do the formula, but then I can also look for light areas or heavy areas or whatever. To get an assessment you count the number of heads in that metre of row, measure out your metre of row, count the number of heads, then work out average grains per head. I count ten heads and I have a look and before I start counting I make an assessment if 60% of the heads are around one size, or reasonable size, 20% are great big heads and 20% are small heads, I’ll do six average ones, two small ones and two of the big ones trying to get an average across them. 
I only count one side of the head. Over the years I’ve done a lot of counting on both sides and I find that one side is basically 50% of the grains so I just double it. 

Then the formula is the number of grains per head, multiplied by the number of heads, multiplied by a factor of 0.027 to 0.029.That’s to take account of grain size per thousand grains, and divided by the row spacing in centimetres. So if it’s a 25cm row spacing you’d obviously divide by 25. 
I try and do three of those counts on average areas in the crop or an assessment on whether its thick or thinner areas and the percentage of those, but I make sure I get a good walk through the crop so I’m getting an assessment. I tend to do a loop, I can go 100m or at times more if I’m not satisfied that I’m seeing an average, but usually a loop of 70-100m out from where you start and come back to that point gives you good idea.
What are some other factors to consider? 
Paul: Certainly grain size and grain development. So I rub the grain out of a number of heads just to see how big and plump the grain is, and whether it’s affected by having screenings of small grain, or may have some other factors there. 
Disease is a big issue. And that’s one of the reasons for doing a reasonable walk through the paddock to try and see of there’s disease there and if its there, how prevalent it is, how much of it and what impact that might have on a crop. They are the heads that you certainly need to look at to see if the grains going to pinch up and whether its going to blow out the back. 
Other issues that you look for are frost damage because that’s going to reduce the size and the amount of grain per head, but its also important to remember if you had 50% of a head frosted that does not necessarily mean you’re going to have 50% yield loss because the remaining grain is going to be large and plump to make up for that. So the density of the crop, that’s going to influence head size and grain numbers per head. 
Another issue that judges need to be aware of is the maturity of the crop. Because if you’re getting a crop that is still quite green then you need to assess certainly the soil moisture, you can judge that by looking at it and just scratching with your heel to see if there’s enough moisture there for that head to finish. If its very dry and the grounds cracking and powdery and the ground’s coming under stress, then that could indicate that the head may not fill to its potential so you end up with smaller grain, not necessarily screenings but the grain doesn’t reach its full potential, compared with a crop that is fully mature, big plump grain, its already there. But sometimes you come across a crop that is in very early stages of development in terms of grain size. That becomes very difficult to assess and basically all you can do is try to determine in your assessment whether there is enough moisture in the ground to enable that crop to finish or whether its just going to struggle later in the season. 
I find one of the most critical aspects of judging the crops is always to give feedback to the grower. Whether that be just on the areas that you’re judging, whether it’s a nice even crop, whether it’s a high yielding crop and general comments. But also give him some feedback on problems that you may have found that the grower can address or may be able to address in the future to help him to grow even better crops.
Paul Parker, District Agronomist, Young; Karen Roberts, District Agronomist Parkes and Tracy Reid, Customer Service Officer, Forbes (NSW Department of Primary Industries) With thanks to Jim Broughton, “Windrush”, Young.
For further information: www.dpi.nsw.gov.au or contact your local district agronomist

p 	How to estimate wheat yields- transcript

How to estimate wheat yields- transcript  p