Estimating Hay Yields on Research Trials

Estimating yields on alfalfa or other hay crops can be challenging. Hay harvesting in the desert SW United States involves a period of curing and baling on dew moisture. Raking and Baling may occur at 3 am in the morning. We like to rise early here in the hot desert, but unless one sleeps in the field, one will miss the bale count. So here is our compromise to the traditional bale count to estimate yields on large research plots. We have used this method for a variety of trials ranging from fertility to soil amendments to soil micro-organism trials (seen here).



Here is a list of items needed: A field that had been cut. A pick up truck with an arm swung out off the bed of the truck. A milk scale. A tarp. Rakes. Measuring tape. Zip lock baggies. Clipboard. Pen. And a couple of assistants.



First measure a length of windrow in replicated plot with the tape.



The length of windrow is raked onto the tarp.





The tarp is weighed, the weight is recorded on the clipboard (don't forget to post the tare weight).



A sub sample of the hay is placed into the zip lock bag. The bag is returned to the lab for dry matter test.

Yield is estimated by back calculating the net weight of the hay to tons/ac. Moisture content is then corrected by dividing the yield by the percent dry matter found from the lab analysis. Yields are commonly reported on Dry Matter or 90% dry matter basis.

Real Time Soil Moisture Reports

Recently new IT products allow traditional soil moisture meters to update to the internet to give reports in "real time".

The report to the right is an example of how soil moisture is depleted from the rootzone of an established cotton crop. Note that root depth can be estimated by the zone of water depletion in that area. For example, the 32 inch sensor began to show water just prior to the last irrigation on July 15th. We can assume that the roots are now in the vicinity of that sensor. http://www.aquaspy.com/Home.aspx

Rain Event

As the old Arab saying goes "All sunshine makes a desert", so it is that I post a recent rain event here in our valley. We received 2.28 inches of rain Tuesday morning. This event was recorded by our Decagon Echo data logger and connected instruments. *see image.

The bar graph shows the rainfall amounts with 1.4 plus inches of rain falling between midnight and 1 am. Capacitance soil moisture sensors responded to the moisture from the rain event. First the top foot (red line) responded. Then the second foot (yellow) and even the deep soil moisture sensor (green line) at 36 inch depth increased. This field is in alfalfa and irrigated by center pivot irrigation system. Due to high water demand (ETo) and limited water supply, it is difficult to refill the soil profile this time of the year to the deep sensor. But it was accomplished by the precipitation that night. Note green line appears at about 4 am after the water had infiltrated to the depth.