Yellow Streaks and Spots in the Lawn
Yellow streaks and spots in the lawn are caused by a permanent soil condition. The actual problem is iron chlorosis (iron deficiency) which is – you guessed it – a lack of iron. Chlorophyll and to a small extent the mitochondria contain iron and when there is low iron there is less of these organelles and the turf turns yellow.
The cause is the soil pH being too high or low making iron unavailable in sufficient quantities to keep the grass green (in Pinellas County it is likely to be high pH). The condition is aggravated in the summer season of rapid growth and heavy rains keeping iron demand high and supply low.
The solution is supplemental iron. This can be done from several sources, the best and most lasting is chelated iron but is very expensive. A good alternative is iron sulfate. Both need to be applied on a regular basis because even the best of conditions the iron will soon be made unavailable by the soil pH.
For the homeowner this is a difficult problem to solve. The best solution is to use turf fertilizers with high iron content. The iron content can be found in the analysis on the bag. Also Millorganite is a good (but expensive) source and a very good product to keep the yellow out. With Millorganite be prepared to use 50 - 100lbs per thousand square feet or about 5 – 10 bags for an average lawn
I use a water soluble blend of natural iron chelates and iron sulfate to produce spray that is long lasting and economical. For the nitrogen fertilizer blackout periods in 2011, I will rely on the more expensive chelates to keep the grass green in an effort to mask the effects of low nitrogen.
ILoveTurf.com - July 15th, 2010
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