Between the Rows: Improving our Corn Silage Harvest Timing
Greg Roth
Department of Crop and Soil Sciences
Penn State
March 2002
This is my first Between the Rows since I left last September for a six month visit to the Miner Institute in Northern New York to study corn silage and dairy cows. Now after going through another silage harvest here with my Miner experience under my belt, I thought a few comments on silage harvesting might be in order.
My hosts at Miner, Ev Thomas and Dr. Charlie Sniffen, continually reinforced to me the idea that to make milk, cows need good and consistent forage quality from both hay crops and corn silage. The Miner staff conducted a survey of active farms a few years back in their area and found that there is a wide range of corn silage quality being fed, dispelling the idea that silage is silage.
There are many factors that influence silage quality but perhaps the biggest one is the timing of harvest. Harvesting too late is especially devastating. Late harvested silage (>40 % DM) generally has lower fiber digestibility, harder kernels, less sugar and slightly lower yields than that harvested in the desired moisture range. It also packs less well and is more subject to yeast and molds. All of these factors could result in 2 lb less production per cow, translating into a $10,000 loss annually on a 100 cow herd.
Even though we all realize the issues with harvesting silage too dry, it still happens quite often- probably too often. We need to work at avoid late harvesting of silage.
This year several extension agents and I initiated a corn drydown demonstration at Landisville. We monitored the drydown of three types of corn early-planted normal, late planted normal and early planted drought stressed. You might have seen some of the reports in Lancaster Farming.
We learned several things in the process- the corn was dryer than it looked at times and it dried down about as fast as anticipated. Also as the corn got dryer, the sugar content of the silage declined. These are exactly the reasons to be moisture testing- not guessing on silage moisture.
So one of the first steps at improving our ability to harvest silage on time is to do more moisture testing both prior to harvest and then during harvest. Moisture testing should start just after all the kernels are dented and a milk line starts to form. Then estimate the time to harvest using a drydown rate of 0.5 to 1.0 percentage units each day. This year our drydown rate averaged about 0.6% per day until the crop reached about 60% moisture, then it increased dramatically.
On farm testing during harvest gives you a clue about whether to speed up the filling process or whether to stop or change fields. On the Miner farm and on several Pennsylvania farms I've visited, it's the responsibility of the guy packing the silo to monitor silage moisture with a Koster tester or a microwave.
Moisture testing should give you heads up on scheduling harvest. With the trend for more custom harvesting, this should help folks get started earlier and work later if necessary or possible.