The main problem concerning corn cultivation is water stress: the most critical phases that suffer from water shortages, which can lead to significant production losses, are from the emission of the plume to flowering and the ripening stage.
In order to obtain high yields, it is necessary to satisfy the evapotranspiration demand of the crop, which is between 0.16 and 0.22 inches/yard per day.
For this reason, it becomes essential to select an efficient and economical irrigation system. The market offers various systems including the most well-known and widely-used option of central pivot and the newer solution of drip irrigation.
What are the differences between the two systems?
Among the relevant differences to consider is the investment cost, adaptability to the rotation, weather conditions, irrigation availability and the efficiency of any fertigation.
Pivot vs Drip irrigation: economic comparisons
In a study conducted by the University of Turin, the costs and efficiency of the two systems were analyzed. Researchers considered the same water supply and an average life of 10 years for the surface drip irrigation and 20 years for the pivot.
According to that study, drip irrigation requires a cost of $1,711 per acre, of which 50% is due to the hoses. The efficiency is between 0.90% and 0.95.
Meanwhile, the central pivot requires a cost of $720 per acre, of which 50% is due to depreciation. The efficiency is between 0.8 and 0.85.
In practice, these figures will be influenced by various factors such as the yield and market price of corn, the extent of cultivation and the effective duration of the system, which depends on the proper design and maintenance.
In fact, according to a study carried out by the University of Kansas, the performance of the pivot system is always higher than a drip irrigation system on large surfaces. The pivot system has maximum potential when the yield and the market price are high; for example, when the yields are above 28.8 Mg/acre and the price is above $108/Mg.
If the price isn't lower than an average price of $108/Mg and the yield is above 31.2 Mg/acre, the drip irrigation system can be equally advantageous in large areas.
In general, the drip system is suitable for small surfaces, while the central pivot is much more efficient in extensive corn crops, and when the yield and market price are rather low.
Pivot vs Drip irrigation: practical aspectsAlthough economic analysis strongly affects the selection of an irrigation system, other practical aspects should not be overlooked. These include water supply and quality, operator skills, crop physiology, and weather conditions.
The plant physiological response to the two irrigation systems is different: the root system develops superficially using drip irrigation while the root system extends in-depth using pivot.
For this reason, fertigation is integrated into a drip irrigation system: this provides the nutrients that the superficial roots cannot obtain in the deeper soil layers. Additionally, fertigation makes it possible to postpone the distribution of nitrogen at the beginning of the flowering phase.
To optimize the advantages of fertigation with drip irrigation, it is necessary to have good quality water. The water must be characterized by low quantities of boron or else the drippers could become obstructed and therefore the useful life of the system could be reduced.
Regarding weather conditions, it is essential to evaluate the windiness of the area. A strong windiness induces differences in distribution and excessive water consumption, which compromises the efficiency of the central pivot system even if the option is economically profitable.
Also, crop rotation is another factor to consider. When irrigation is not essential for all crops in rotation or the switch from monoculture to polyculture is frequent, the central pivot may not be practical and efficient. In such cases, drip irrigation could be more effective; although, it entails an expensive investment to dispose of the hoses at the end of the season and to provide the labor involved in disposal operations.
Water supply is also a relevant critical factor: in areas where this is limited, a drip irrigation system is preferred especially for heavy soils and small lands as this enables optimizing crop intensifications (9 -10 plants per yard). On the other hand, a drip irrigation system requires constant water supply given that the irrigation events are frequent and apply short volumes.
In conclusion, it isn’t possible to say that one system is universally better than another. The differences between the two systems are many and must each be individually assessed in order to make a choice that’s economically and environmentally optimal.