Nitrogen's Lasting Effects

[JHazzardB]

No soil test here, just a soil question.

I've allied nitrogen (.5lb/K) to my yard twice this spring. Basically when it was waking up in February and maybe hit it again in March. Since then I've been coasting on rainfall and don't plan on adding anymore until fall.

How long does Nitrogen last in the soil? Does it wash through quickly? My yard is growing between 2-3 inches a week right now with all the copious amounts of rain (22" so far). But then, I start to wonder 'how much is due to rain?' or 'how much is the pound of N that I dropped in spring?'.

I'm thinking the N has passed through and it's just loving the rain.

Side note: has anyone ever pondered a relationship between "Lb/K of N" : "Inches of growth"? Have you ever though, 'right now, that .5'lb of N should get my 2.5" of growth over the next week'? That sounds like a can of worms.

[TimmyG]

How long does Nitrogen last in the soil?

Not long, as it is used up by the plants just about as quickly as it becomes available. Quick-release (water soluble) nitrogen like urea is taken up by the plants roots quickly. Slow-release (water insoluble) nitrogen, be it organic or coated synthetic or other, becomes available over an extended period.

If you don't have plants in the soil, then it may leach into groundwater and/or volatize into the atmostphere, but it won't persist in the soil like phosphorous and potassium.

[andy10917]

+1. Nitrogen levels in the soil are notoriously fickle and difficult to pin down. They can even change hourly and day-to-day, and you should notice that we don't even use them when writing soil plans - we just make sure some is always present.