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Q
Hi , Maximum Yield ! I have a question : If I have 42 ppm of NO 3 in the soil where I plan to plant corn , is it better or not to use a starter basic fertilizer ?
A
Hello ,
Thank you for your question . The pre-sidedress soil nitrogen test ( PSNT ) was developed by Dr . Fred Magdoff at the University of Vermont to help make an accurate nitrogen ( N ) fertilizer recommendation for a corn crop . The test assumes the soil has had an application of manure , a cover crop that contributes to the N in the soil , or has had a previous application of nitrogen . The PSNT test displays the needed concentration of N in the nitratenitrogen ( NO 3-N ) form . Research done in many states has shown that when 25 ppm of NO 3-N is present in the top foot of soil , additional N applications are not necessary . However , if the NO 3-N level in the top foot of soil is less than 10 ppm , the full recommended rate of N would most likely be necessary . In other words , for a corn crop to have all the N it needs to grow properly , the soil needs to have a concentration of 25 ppm of NO 3-N or greater . Soils with a concentration of NO 3-N below 10 ppm would need to be fertilized at the full recommended rate , whereas those with a concentration of NO 3-N between 10-25 ppm may need supplementary fertilization ( that is , less than full strength ). From your soil sample , we know the concentration of NO 3 ( nitrate ) in the soil is 42 ppm . However , to use the PSNT with your soil test results , we need to convert your NO 3 value into a NO 3-N value . To convert NO 3 to NO 3-N , we multiply the NO 3 value by 0.226 . So , in your case , the NO 3-N value for your soil is 9.49 ppm ( 42 ppm x 0.226 = 9.492 ppm ). As you can see , your NO 3-N value is less than 10 ppm .
This means it would be a good idea to use a fertilizer at its full recommended rate to help raise the concentration of NO 3-N in your soil . Keep in mind , it is possible for the concentration of NO 3-N to build up over time with the addition of organic matter ( be it manure or cover crop ) or fertilizers . Therefore , it is a good idea to test the soil for NO 3-N concentrations each year prior to planting as your soil ’ s NO 3-N concentration could raise above 10 ppm over the course of the year . Hope this helps .
Keep on Growing , Eric Hopper
Eric Hopper ’ s past experiences within the indoor gardening industry include being a hydroponic retail store manager and owner . Currently , he works as a writer , consultant , and product tester for various indoor horticulture companies . His inquisitive nature keeps him busy seeking new technologies and methods that could help maximize a garden ’ s performance .
INCREASE IN NITRATE ?
Nitrates are produced for use as fertilizers because of their high solubility and biodegradability . The main nitrate fertilizers are ammonium , sodium , potassium , and calcium salts . An increase in any salt will increase the osmotic concentration of the soil solution . The roots of the plant then have to take up minerals from a more concentrated solution . If the solution gets too concentrated , there will come a point where the plant is not able to take up any water against the concentration gradient and the plant will start to wilt . Even before this point is reached , the plant will grow slower .
- saps . org . uk
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