I have aquired a potted moro blood orange which was on its way to an early death. It was badly root bound and lacking in what seems like all areas. It lost about 2/3 of all it leaves and lost about 1/2 of all it branches. I repotted it into a 2' tree box it lives outside here in southern Riverside county. It has responded with what seems like a large flush of growth, leaves and buds as well. I want to increase the nitrogen levels in the remaining foilage as it seems it is still quite pale/yellow to me. I am fertilizing with a combination of Bandini slow release granular citrus food (16-4-8) and two water soluable fertilizers, Citrus MoreGro (20-10-15) and Miracle Gro acid loving (30-10-10). I am limiting the soluable levels to 300ppm of Nitrogen each watering. We have had a good amount of rain lately, so I don't really want to add more water to the soil as there may be more rain on the way.

Now to my question, how often can I apply soulable fertilizer to the leaves (foliar) without burning the leaves. At what ppm levels are benficial? How high can I go before I burn the allready stressed leaves?

Pics follow:

Thanks,
Pat

When a fertilizer formulation doesn't have foliar instructions, you can still usually apply it as a foliar application, but apply the product at a rate of 10 to 15% of the maximum root application instructions (especially if the product is rather high in N-P-K). It is probably best to avoid the really high NPK chemical formulations, which are best left for root application. Plants can absorb nutrients 8 to 10 times more efficiently through their leaf surfaces than through their roots. When applying nutrients to the leaves, the nutrients enter through the stomata, then travel downward through the plant at an average rate of about a foot an hour. With foliar sprays, as much as 95 percent of what is applied may be used by the plant. A similar amount applied to the soil, about 10 percent of it is available.

The "law of small amounts" always applies to foliar feeding. It is better to spray small amounts of material more frequently than to drench the foliage with large amounts of material. Small quantities of major elements such as nitrogen "speed up" the physiological functions of the plant. If foliar feeding is done correctly, visual results from some elements may be seen within 48 hours. - Millet (1,426-)

Another reason for not applying foliar sprays during the heat of the day, is that the efficiency drops dramatically, because the sun and the heat quickly dries the spray, making it unavailable to the plant. - Millet (1,426-)

Thanks for your responces. Based on these I think I now have a good grasp on how much the plant can handle per feeding without burning.

Millet wrote:

The "law of small amounts" always applies to foliar feeding. It is better to spray small amounts of material more frequently than to drench the foliage with large amounts of material. Small quantities of major elements such as nitrogen "speed up" the physiological functions of the plant. If foliar feeding is done correctly, visual results from some elements may be seen within 48 hours. - Millet (1,426-)

Would once or twice a week be too frequent when using a 1% solution of a complete NPK fertilizer? It seems that foliar absorption is quite quick and that results may be visible quickly as well.

~Pat

Probably not, but if you are feeding your tree through the roots at 300 PPM, on a continuous basis, the tree will not also require a frequent and continuous foliar spray program. - Millet (1,426-)

Joe, that a good Point. - Millet (1,426-)