A. C. Mahony
It is essential to analyze the differences in the sustainability of irrigation systems and which would best fit your farm—certain irrigation methods, when implemented and monitored properly, can increase sustainability by optimizing profits, water usage, and onion yield. Research conducted by the Malheur Experiment Station, among others, has shown that drip is the most sustainable irrigation method for onion production because it minimizes off-site soil and nutrient losses, decreases risk of onion rot and disease, and conserves water with more precise application in comparison to sprinkler and furrow (flood) irrigation systems (Shock, C. C., Flock, R., Feibert, E., Shock, C. A., Jensen, L., & Klauzer, J., 2013; Shock, C.C., 2013).
Drip irrigation can be used to optimize onion quality while minimizing water stress on the onion. Drip can also sustain higher yields and larger bulbs, reducing the chance of disease within the onion because of the direct, underground application of water (Shock et al., 2013). In this way, drip irrigation can minimize fungicide usage and costs. Drip irrigation also makes weed control more efficient because less water is applied between onion beds to satiate weeds, minimizing herbicide usage and costs. When drip irrigation is used with fertigation, it can reduce the use of excess nitrogen fertilizer with its precision. Current irrigation system designs already in place, irrigation automation systems, and amount of water available are other factors that need to be considered when deciding how to best apply drip irrigation to crops and maximize efficiency. Installing drip irrigation requires a large start-up cost; however, the saved water and profitability of drip irrigated onions can make the investment worthwhile (Shock, 2001).
Sprinkler irrigation sprays water fairly uniformly on the tops of crops, making it less beneficial for onion production in comparison to drip irrigation. Sprinklers spray water directly on onion leaves, increasing the risk of fungal and bacterial disease development while decreasing marketability. They also spray on the soil around the onion, providing an ideal environment for weed seed germination. Sprinkler irrigation increases the need for pesticides and fungicides, ultimately increasing costs of onion production in comparison to drip irrigation. If a grower already has a furrow irrigation system, drip and sprinkler systems increase capital costs and reduce labor costs compared with furrow irrigation; also, labor costs related to center pivot sprinkler irrigation are lower than those of drip irrigation. Both systems can also be successful as means of fertilization.
Furrow (flood) irrigation directs water down crop rows to water plants. This is the least efficient irrigation method for onion production because more water, topsoil, and nutrients are leached and lost in runoff than with drip or sprinkler irrigation. Water application with furrow is not as easily monitored or regulated as drip or sprinkler, nor is it as uniform. However, with intensive monitoring and surge irrigation, furrow can be made more sustainable to minimize off-site losses.
Refer to additional resources according to the geographical location and current assets of your farm for further information.