There are times when the development of one technology supports the development of another. There are also times when one technology demands another. The postwar development of irrigation both supported and demanded the development of artificial fertilizer, and vise versa.
Before the irrigation boom of the late 40s, farmers counted on the natural fertility of the rich land to supply their crops with nutrients like nitrogen and potassium. Many would use natural fertilizers like manure. Or they rotated their fields, planting crops like alfalfa that replenished nitrogen in the soil every third or fourth year. The next year, they would plant that field back to corn or another cash crop.
But when a farmer made a big investment in an irrigation system, he or she had to plant cash crops every year to pay off the new system. Natural sources of fertilizer didn’t supply enough nutrients and couldn’t be controlled easily. Intensive cropping patterns were sucking the nutrients out of the farmland.
One writer for a farm magazine in the late 1940s wrote, “constant cultivation is exhausting the organic content of the soil.”
So, the technology of irrigation was crying out for new technologies in fertilization. Private companies and the government responded. By the late 1940s, they had shifted their production of nitrogen for bombs to the production of nitrogen for farms.
At first, nitrogen was supplied in pellets that were scattered on the ground. But by the end of the decade, chemical fertilizer was produced in a gas form – anhydrous ammonia. “Anhydrous” (as it became known) was almost 80 percent nitrogen and was manufactured from the air or natural gas. It could be distributed throughout the Midwest via pipelines, an extremely inexpensive mode of transportation. And by 1950, a Texas firm had developed a way for individual farmers to inject the anhydrous directly into the soil.
Irrigation demanded the development of commercial fertilizer. On the other hand, fertilizer demanded irrigation. 
Manure and rotated crops were essentially free. When a farmer started using commercial fertilizer, uncertain rainfalls put that investment at risk. If a drought year hit, the entire fertilizer outlay could be lost without irrigation.
Jim Chenault (right) knows the dilemma well. On the one hand, his irrigation system and operation is a big expense. On the other hand, it makes his investment in fertilizer much less of a risk. “The knowledge that you can plant heavy, [and] fertilize heavy – because you will have the water if you need it – is worth a lot.”
Written by Bill Ganzel, the Ganzel Group. A partial bibliography of sources is here.
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