Due to high ammonia prices, farmers are shifting from corn to soybeans. This is to use less of nitrogen. However, they both still need potash! Conclusion: when natural gas rises, ammonia rises and potash will rise.
Corn uses an N-P-K ratio of 120-80-80.
Soybeans use an N-P-K ratio of 0-70-100. No nitrogen is needed because they get the nitrogen from fixating bacteria into nodules that produce plant available nitrogen.