Fertigation is the distribution of water-soluble fertilizers through drip irrigation. Think of it as precision nutrition. The nutrients are diluted concentrations of, mainly, potassium, nitrogen, and phosphorus. Fertigation delivers the right dosage at the right time in the amount needed by the target crop. The delivery system is a set of pumps and valves that feed small pipes to drip the nutrients to the plant roots. The pipes may be either underground or on the surface.
Fertigation is part of the comprehensive and urgent move to precision agriculture which applies technology to narrow down every use of scarce resources to pinpoint accuracy. Drones can now target single plants for water and pesticide treatment or weeding. Electrochemical sensors are able to detect specific ions in the soil and identify clay, organic matter, and moisture content. Artificial Intelligence neural models are beginning to accurately detect disease symptoms in a single plant from electromagnetic light invisible to the human eye.
The direct contribution of fertigation to precision agriculture is twofold: (1) fertilizer use, and (2) responding to water shortage.
The chemical composition of tea fertilizers has required that they be prediluted to keep them in suspension, making them weaker and low in concentration. Fertigation regulates the balance, reducing fertilizer volume and cost while ensuring strength and effectiveness. This is not a simple matter of pour and stir but involves situation- and equipment-specific proportioning mathematical equations. Nor are the nutrients confined to the N, P and K combination; one line of development is the use of compost tea waste as an organic fertilizer. The core requirement is that the nutrient be water-soluble. It can then be mixed, managed, filtered, injected and scheduled precisely, not broadly.
It also reduces water use. The latter is moving rapidly up in priority on the global policy agenda and in farming practice. In many regions of Asia and Africa, water shortage is at a crisis level. Droughts, shifts in seasonal rainfall, and water deficits are commonplace, not exceptional. This is happening in a context of declining crop yields when most estimates are that agricultural production must increase by 70% over the next decade to meet the demands of population growth.
Here is where the irrigation component of fertigation comes into play. It is not new in either concept or practice and is basically plumbing systems. It’s a more precise way of watering crops than traditional spraying and sprinkling. These have many inefficiencies. In dry seasons, they may stress the soil and add to erosion. In wet ones, they create waterlogging and runoff and can leach the chemicals. Overhead sprinklers are hit or miss and erratic in their precision and pressure. They distribute fertilizer (and pesticide and fungicides) broadly not precisely. You can literally see the water being wasted. Netafim, the largest Indian irrigation service firm, reports that flood irrigation reaches only 30% of the land, sprinklers 60% and drip irrigation 90%.
The science and practice of fertigation are well-established, with an experience base dating back for decades. The core is drip irrigation. The goal is to place water directly into the root zone and minimize evaporation – feed the plant, not the soil. It’s sometimes appropriately termed trickle irrigation. This can save both water and nutrients by allowing water to drip slowly to the roots of plants, either from above the soil surface or via pipes buried below it.
The classic and widely-referenced summary of the economic benefits of tea fertigation was published in 2008 but based on work started out in 2003 in Tanzania. It applied four schedules and identified an optimum schedule and nutrient flow, after which there were declining returns.
Tea is Tanzania’s fifth-largest export crop, generating $30 million in foreign exchange. Around 20% of gardens use sprinkler irrigation, often subjected to high winds that scatter the water flow. Almost all the rest is from rainfall – “flood irrigation.” Drip irrigation doubles the production of green leaves of harvestable quality.
The Tanzania affidavits for fertigation are consistent and compelling. The obvious problem is financing and management expertise. The subsystem of one 635 hectare farm in the trial consisted of a pump unit, filtration, and fertilizer injection unit, block valves, and surface driplines spanning two rows of bushes. This has been improved on but provides a baseline for a standard configuration.
Here are examples of benefits:
- The average yield for 3-year old bushes increased by 25%. For 4-year old plants, it was 48% and 52% for 5-year old ones.
- Labor savings were 48% and power reduction 16% versus sprinklers. Fertilizer costs were lower in all instances. Less weeding was required. Shoots regenerate faster and bush mortality is lowered.
- Other case studies show comparable gains:
- In South India, one extensive tea garden increased its yield from 3,500 kilos to 5,000 in four years and to 7,000 in nine. The owner reports a visible improvement in the health of the plants. A Sri Lanka three year development doubled yields.
- Another study of clonal tea impacts also reported a doubling.
- Several bioconversion projects show promising indications in converting cow dung and tea waste into soluble microorganisms for fertigation delivery.
The cost of fertigation systems is around $9 per hectare. For a smallholder, the estimated investment is about $4,000. The price listing for commercial-scale fertigation automatic machines averages around $6,000. Management skill is the main limiting factor in planning, operation, and benefits. Fertigation involves careful oversights, maintenance, and judgment.
Fertigation systems scale easily and their modular components permit incorporation of new technology quickly and incrementally. Ongoing developments exploit wireless sensors for image capture from drones that provide details on terrain, soil, undulation patches, pH levels, humidity, and many other factors that can be input to the fertigation mixes and injectors. AI backpropagation machine learning can build up patterns from experience that can link to the fertigation systems for real-time adjustment and early warnings. A growing range of fertigation software develops recipes for nutrition, procedures for handling varying pipe lengths, clogging and filtration, and scheduling. This, again, requires new management skills.
Fertigation will be evolutionary in its expansion across the scattered, fragmented, remote and varied terrains of tea growing. But it is a sure winner and an opportunity now, that will become a necessity as climate change accumulates its impact.
70% of all the freshwater in the world goes to the irrigation of agricultural crops. Since 2000, the rate of melting of the Himalayas has doubled.