The present invention relates to methods for fertilization by adding fertilizer nutrients to agricultural irrigation systems.
The agriculture industry adds fertilizers to the plant environs, such as the soil, to enhance crop growth and subsequent yields. Commercial fertilizers are usually selected of a variety of formulations depending on the crop and its nutrient requirements.
Fertilizers generally are classified according to their NPK content. NPK is common terminology used in the fertilizer industry and stands for: (1) N—the amount of nitrogen in the formulation as N; (2) P—the amount of phosphorus in the formulation as P2O5; and (3) K—the amount of potassium in the formulation as K2O. Nitrogen, phosphorus and potassium are the basic plant nutrients or macronutrients that are taken up and utilized by the growing crops, and they are commonly provided or augmented by the addition of fertilizers (NPK fertilizers).
A fertilizer, as that term is used herein and as generally understood, refers to the nutrient-containing materials used to deliver fertilizer nutrients to a crop. Conventional fertilizers typically will contain materials that are extraneous to the crop's nutrient-uptake and soil condition (“yield-extraneous constituents”) but which, for practical and/or other reasons, are necessary to the delivery of the nutrients. The process of delivering fertilizer nutrients to crops is referred to as fertilization.
The fertilization method of adding fertilizers to the water being used to irrigate the crops is called “fertigation”, reflecting this combination of irrigation and fertilization. Fertigation reduces equipment, fuel and labor expended in the addition of fertilizers in comparison to mechanical delivery of fertilizers to the crop, and thus fertigation achieves a significant overall cost savings.
To conserve water, which is decreasing in availability and increasing in cost, current conventional technology includes micro-irrigation systems that deliver precise amounts of water directly to the soil holding the root system of the plant that is being grown. In the past twenty to thirty years, a large percentage of crop producers in the western and southwestern United States have converted from flood and sprinkler irrigation systems to micro-irrigation technology. Micro-irrigation systems contain devices called emitters, micro-sprinklers or other such devices that provide the precise amounts of water directly to the desired soil site, namely the soil holding the roots of the plant or crop being irrigated.
Micro-irrigation systems are sensitive to water quality and the inclusion of fertilizers and other additives stemming from the refinement of their micro components. These emitters, micro-sprinklers or other micro devices have very tiny orifices and/or a long tortuous narrow passageway that provide the requisite pressure for delivery of precise amounts of water in a uniform manner to each plant in the crop being irrigated so long as deposits do not build up inside them. Deposits from any source foul or plug these micro components. The smallest particle or foreign material can cause fouling of these devices. Water quality and the inclusion of fertilizers can, and frequently does, cause severe plugging problems. The problems arise from a number of factors: (1) the irrigation water is typically obtained from wells, reservoirs, canals, lakes, or rivers which contain various amounts of dissolved minerals; and (2) fertilizers can form insoluble salts and/or cause particulate formation when added to the water. Macro-irrigation systems (macro-sprinkler irrigation systems) mainly tolerate these conditions, while micro-irrigation systems are extremely intolerant.
In more detail, the addition of conventional fertilizer formulations to irrigation water normally increases the loading of inorganic salts over that already in the water. When the loading, or the combined loading, is too high, the solubilities of at least some of the naturally-occurring irrigation-water minerals and/or added compounds are exceeded and particulate formation increases dramatically. When particulates form, significant deposits begin to build up throughout the irrigation system. The end result for emitters or micro-sprinklers is plugging.
Plugging results in uneven distribution of water and nutrients to the crop being irrigated, and in some cases, the complete shut-down of the micro-irrigation system. Problem-free use of additives such as fertilizers in micro-irrigation systems is normally seen only in irrigation systems that use relatively pure water sources.
The conventional agricultural practice is to make intermittent or periodic applications of fertilizers. Such intermittent or discontinuous additions might be a single addition, or a plurality of additions, of large amounts (high concentrations) of fertilizer during a brief time interval each growing season or crop cycle. (The number of applications per growing season or crop cycle usually depends on the crop and/or the type of fertilizer being added.) When the fertilizer-delivery method is fertigation, fertilizers are typically slug fed into the irrigation system as quickly as possible to minimize the labor requirements and ease material handling. Slug feeding of a block (portion of a field) normally entails feeding the large amounts (high concentrations) of fertilizer to the irrigation water over a six to seven hour period during irrigation, and then, after the fertilizer feed is shut off, continuing the irrigation of that block for an additional two to three hours to rinse out all of the fertilizer that is contained inside the irrigation system, insuring that all of the fertilizer intended for the block is in fact delivered to the block. When an entire field is irrigated on a single day, slug feeding does not require a post-fertigation rinsing period.
The cost of commercial fertilizer formulations is, however, itself significant, and commercially viable fertilizer formulations (formulations sufficiently inexpensive for bulk agricultural use) typically include, as mentioned above, yield-extraneous constituents which do not contribute to plant nutrition or soil condition, and can even be undesirable components. Further, the bulk weight of commercial fertilizer formulations typically is water which increases the shipping costs. The water of a fertilizer formulation is analogous to, or at least approaches being, a yield-extraneous constituent because its contribution to the water requirements of a crop normally is negligible, particularly in comparison to its adverse impact on shipping, storage and handling but since water is normally required for an unimpeded container-to-irrigation-system fertilizer addition it is analogous to, but still not considered herein, an essential yield-extraneous constituent.
The terms “micro-irrigation” and “macro-irrigation” as used herein refer respectively to (1) micro-sprinklers, drip, and subsurface drip systems and (2) sprinkler systems without micro components which are primarily overhead sprinklers. The terms “overhead sprinkler” and “overhead sprinklers” as used herein refer to irrigation systems in which the irrigation water is emitted or sprayed from sprinkler heads, nozzles or other irrigation devices disposed at a position elevated from ground level, that normally (but not necessarily) are engaged directly above the crop being irrigated. Overhead sprinkler irrigation systems are normally macro-irrigation systems because micro-irrigation normally depend on a close proximity between the emitters and soil immediate the crop while overhead sprinklers are normally spaced apart from the soil immediate the crop. Such micro- and macro-irrigation systems are collectively referred to herein as “emitter-irrigation” systems because they each emit or eject sequential small quantities of irrigation water from irrigation lines or tubes directed more or less towards the crop being irrigated.