Sally A. Flis, Ph.D. – Feed and Crop Support Specialist, Dairy One
Kevin Putnam – Dairy Specialist NY/NE, DuPont Pioneer
There have been lots of question and concern in the drought stricken parts of NY about nitrate levels in corn silage and when or if dry matter (DM) is at a level to chop already. As of last week, 44.6% of NY was in moderate drought or greater, with 27.2% still in severe drought and 6.0% in extreme drought (Figure 1).
Figure 1. August 23, 2016 NY drought conditions.
Drought stressed corn will often look like it is dry enough to harvest for silage because of the visual effects of drought stress, curled leaves, small or no ears, and stunted growth. The fact is that this corn can take longer to dry out because of the small or lack of ears and dry leaves do not reflect a dry stalk. Additionally, nitrate accumulation in the plant can be a concern when plants experience drought stress. Nitrate is a major precursor of plant protein. Ensiling suspect forages can often reduce nitrate concentration by up to 50%.
So, what does this stressed corn look like this year? Samples have been taken over the last 2 weeks and tested for DM and nitrate concentration (Table 1). Dry matter is increasing as moisture leaves the plants, but we are still on average about almost 10% change away from corn being in the ideal range for harvesting for corn silage. Nitrate ranges are well below critical concern levels (< 0.44 % Nitrate). More information on nitrates is available at https://dairyone.com/wp-content/uploads/2014/01/Nitrates-and-Dairy-Cattle.pdf.
Table 1. Corn dry matter (DM) and nitrate results from Central NY.
|Date||Average DM||DM Range||Average Nitrate, %||Nitrate, % Range|
|8/18/16||23.2||18.4 – 31.2||0.06||0 – 0.19|
|8/24/16||26.5||22.5 – 30.1||0.10||0 – 0.27|
Nitrate concentrations in drought stressed corn in NY does not appear to be a problem. This is likely because of late season rainfall causing some addition growth and leaching of nitrates from the soil. Additionally, if side dress N applications were not made due to drought conditions N may be deficient. As with anything else, sampling and testing is the only way to know what your crop looks like.