I once read that the "real cost" of a gallon of fuel delivered to a Forward Operating Base in Afghanistan was in the neighborhood of $400 a gallon.
That seems insane to somebody in the US who is pumping $4/gallon gasoline into their Toyota. It reeks of corruption and incompetence until you start looking at the cost structure.
Start at $4.50 per gallon in southern Pakistan. Then apportion out the cost of maintaining "sanitized" routes through unsecured territory. Also apportion the cost of equipment that is damaged (blown-up, bullet-holes shot through the walls of the tank, damaged tires). Also add in the cost of the security detail that accompanies each fuel delivery along with the real depreciation to their equipment.
Suddenly, $400 a gallon does not seem so outlandish. It is certainly much less expensive than illegal drugs in the US (which are expensive for many of the same reasons).
Fertilizer
Fertilizer has a less hazardous trip from the dock in Louisiana to the cells in the plant you are growing...but there are costs.
The point I want to emphasize is that if you lost a 10,000 gallons of diesel in the outskirts of Islamabad you were out $45,000. If you lost that same 10,000 gallons 500 meters from the Forward Operating Base you were out $4,000,000 because the "cost" incurred between Islamabad and the FOB were squandered.
While the fertilizer is in your care, the bag can tear or you can put it in a damp place and have it turn into a rock or it can get rained on and leached into soil.
The fertilizer you sprinkle onto the soil can be washed away by excessive rains, it can be immobilized by drought (the roots requiring that the nutrients be dissolved in water before they can absorb them), the nutrients can be poached by weeds or the weeds can suck the moisture out of the soil thereby making the nutrients unavailable.
Some gardeners are casual about weeds, saying that the nutrients are still in the garden...and while that is mostly true, those nutrients are NOT available to the plant you are growing and are counting on to feed you. Disclosure: I favor using plants like turnips and rye to capture nutrients during the "off" season when I don't have other food-plants actively growing. But pay attention to the fact that the "weeds" I use for that particular purpose are edible and they can function as a safety-net if things get really spicy.
Some forms of nitrogen like urea and ammonia will vaporize at high temperatures (again pointing to the wisdom of managing you soil moisture as an integral part of your fertilizer management).
In the soil, some nutrients bind to iron or aluminum ions if the pH is "wrong". You might have an abundance of phosphorous (for instance) and adding more will not help you nearly as much as addressing the issue with pH.
Even after the nutrients managed to dodge flood, drought, greedy weeds, bad chemistry and get into your plant, they can be lost to the plant collapsing due to a stem-disease or a hungry rabbit or deer munching the leaves. Or to cabbage worms or tomato worms or a host of other pests. At this point, you are in the same situation as the FOB that watched the tanker truck take a direct hit from a mortar round 500 meters from the wall. So close. So very, very close.
Fortunately, the events that are "most expensive" in terms of lost nutrients are the ones that are most under the control of the gardener. We can put up fences to deter virtually all animals smaller than elk and moose. We can choose disease resistant varieties and space them out to foster good air-flow. We can control the insect pests.
Weeds deserve a special note. Weeds are not "just another plant". The plants in your garden divert significant amounts of carbohydrates and protein into the food you are going to harvest. Weeds, on the other hand, do not have to "pay" those costs. They grow more quickly. Their roots plunge more deeply into the soil. Their roots have more surface area and so on. Given that your food-plants are operating under a significant handicap, you need to put a very aggressive thumb-on-the-scale to even things out. Remember, weeds short-stop nutrients by stealing them, by sucking the soil dry, by shading your enfeebled plants and by getting a head-start, time-wise, in your garden.
Moving a step away from the garden along the supply chain, timing the application of fertilizers so that they are just entering the root zone as the plants are unfurling their canopy is good business. The plants cannot "pull" nutrients unless they have leaves transpiring water. No leaves, no movement of the nutrients into the plants. The longer the nutrients are in the soil before the plant can pull them in, the greater the losses due to leaching and weeds (which had a head-start).
A step farther up the supply chain, treat the bags of fertilizer (or shovelfuls of manure) gently. Put them on a pallet off of the ground and under a roof that will keep the rain off of it. If you have mice, have a plan to control them lest they chew holes in the bags.
About that nitrogen that leached...
Suppose you have animals and you have been dumping the stable-waste in a pile. If you have been doing it for a while, that pile might be 8' high, 15' wide and 50' long.
Most annuals that we grow in gardens are fairly shallow rooted as noted in the paragraph where I discussed weeds.
However, there is a huge amount of variability. Some perennials like asparagus and horseradish have roots that plunge more than 10' deep (assuming the water table is deeper than that and they don't hit bedrock).
Many varieties of grapes have roots that run deep as do pears, figs and mulberries.
Another possibility is to plant species that are heavy users of nitrogen and use the leaves or cuttings from them as mulch. Or, use them as forage/bedding for your animals and THEN use them for mulch.
Bonus images