Economy
Tire manufacturers recommend their customers to check tire pressures regularly, a 30% under-inflation is nearly invisible and will increase fuel consumption and tire wear.
Checking pressures with standard gauges is too much of a hassle and very often forgotten by machinery operators as they are mostly in a hurry! Improper tire pressures increase significantly the risk of wheel spinning and sinking of the machine into the soil. Improper tire pressures decrease significantly traction force and rolling resistance. Results are an excess fuel consumption, an unnecessary wear on both machines and tires as well as wasted time.
Safety
Incorrect tire pressures are dangerous and may cause rim failures, an uncomfortable ride, tire overheating, tire casing damage, tire rotation on the rim and less steering control.
Wheel or rim failures are rarely caused by low speed field work. The combination of high loads ( mostly overloads ) and high speeds often results in wheel or rim failures causing tire damages and in worst cases tire blowouts. High pressures tires are required to carry the load/speed combination but do not allow any flex or suspension from the tire itself : all shock loads from high speed road travel are transmitted directly to the wheels causing rim or disc failures. Minimum inflation pressures are very close to the point of causing damage to the tires, hence operating tires at minimum inflation pressures does require closer tire management.
Ecology
Compacted soils are a major concern for farmers and agriculturists. Improper tire pressures do cause soil compaction resulting in decreasing crop yields.
Soil compaction is one of the major soil damage processes and is a very serious issue. Compacted soils are less able to absorb water, increasing the risk of erosion and runoff. The easiest way to deal with soil compaction is to prevent it by running machinery with proper tire pressures reducing pressure on the soil caused by the repeated passes by agricultural equipment resulting in ruts in which nothing grows. Ruts are like a step causing, requiring a constant climbing of the tires resulting in increased fuel consumption and serious tire wear. The economic impact of soil compaction is important as it decreases significantly crop yields, risks of soil diseases development and a need to do regeneration work.