J. L. Harden, A. C. Mahony
Fertilizer is needed to support plant growth. It is made up of macronutrients that all plants require to survive: nitrogen, phosphorus, and potassium. Specialized fertilizers can also have different nutrient combinations in order to satisfy the needs of many different plants (What Is Fertilizer and How Does It Work). Although it is necessary for most crops’ well-being, the application of fertilizer can lead to negative outcomes. Much of the fertilizer applied to fields is not absorbed into the soil but is instead lost to runoff or leached into the soil profile, which eventually contaminates groundwater.
Many things must be considered when deciding what kind of fertilizer to apply to crops. Because plants will need certain amounts of nutrients in order to maximize their growth, many soil and tissue tests are completed. This way, the grower knows which nutrients the plants need and can decide on fertilizers accordingly. According to Monty Saunders (2013), soil tests should be done once every year while tissue tests should be completed once a week during the growing season to gauge nutrient levels and general health. Nitrogen fertilizer should be applied to onion crops every 2 to 3 weeks, while a supplemental phosphorus fertilizer can also be beneficial (Growing Onions).
There are various fertilizer application methods that a grower should consider. The four main types of application methods consist of broadcasting, foliar, placement, and fertigation. Broadcasting application means to uniformly distribute fertilizer over an entire field (for an in-depth description, please see Nutrient Management :: Methods of Fertilizers Application. Foliar application means to apply liquid fertilizer in a spray so that it settles on leaves of plants (for more information, visit Foliar Fertilization – Pros and Cons). Placement application means to only apply the fertilizer near plant rows within a field.
Fertigation is an entirely different type of application method. It is the addition of fertilizer into irrigation water and can be applied through drip, furrow, and sprinkler irrigation systems (Combining "Green Industry" with Technology). With fertigation, growers save money, time, labor, and water because they have more control over what is fertilized and what is not. Healthier plants can grow because they are less likely to contract diseases. Liquid fertilizers can also greatly reduce the amount of toxic runoff because chemicals are applied with more precision.
Fertigation can be beneficial to onion crops because it controls nitrogen leaching and saves water, energy, and nutrients through effective water and nutrient application (Jat et al., 2011). Drip irrigation applies water most precisely to the plant in comparison to sprinkler and furrow irrigation; therefore, drip irrigation is the best option in which to introduce fertigation to fields. For more in-depth information regarding equipment specific to your farm’s needs, please visit Fertilizer Injectors: Selection, Maintenance, and Calibration.