Question I have access to corncobs to use as mulch. Before mulching with corncobs I applied 5-10-5 fertilizer. Do ground corncobs rob the soil of nitrogen as sawdust does? Do corncobs add nutrient to the soil when rotted? What kind of lime and how much should be used to make hydrangea really pink? SR, Ill.
Answer Being softer than wood and, therefore, breaking down faster, ground corn cobs do not create a nitrogen deficiency to the same extent as sawdust. When rotted, corn cobs will add some nutrient material to the soil. Hydrated lime may be used to intensify the color of a pink hydrangea, but one cannot say off hand how much may be needed. A soil test is really required. Too much lime will cause a mottling of the leaves. Try a light sprinkling and scratch it into the soil.
