What are the advantages of fertigation in agriculture ? 1. Controlling the alkalinity of irrigation water is possible. 2. Efficient application of Rock Phosphate and all other phosphatic fertilizers is possible. 3. Increased availability of nutrients to plants is possible. 4. Reduction in the leaching of chemical nutrients is possible. Select the correct answer using the code given below :

Identifies micro‑irrigation (the delivery system used for fertigation) as a means to reduce fertiliser/nutrient loss and to apply nutrients through irrigation.

A student could extend this by noting that precise delivery systems allow deliberate addition of chemical inputs to irrigation water, so they could test whether adding specific inputs via fertigation alters water alkalinity.

States that targeted irrigation can control where fertilisers go and can eliminate spread of harmful chemicals through drainage, implying control over chemical composition of irrigation water on‑farm.

One could infer that if irrigation systems control distribution of chemicals, they might also be used to adjust water chemistry (including alkalinity) locally and then test changes in soil and runoff.

Notes that irrigation water in canals can reduce soil salinity/alkalinity in desert areas, showing irrigation itself affects salt and alkaline conditions.

A student could combine this with the idea of adding reagents via fertigation to hypothesize that fertigation might be used to actively modify alkaline conditions rather than just dilute them.

Explains causes of saline and alkaline soils (salt accumulation via groundwater and capillary action), highlighting the chemical nature and sources of alkalinity in agricultural water/soils.

Knowing sources and mechanisms of alkalinity, a student could evaluate whether introducing neutralizing or pH‑altering fertiliser solutions through fertigation could counteract those processes.

States that chemical fertilisers dissolve in water and are immediately available to plants, demonstrating that adding soluble chemicals to irrigation water changes its composition.

A student might extend this to reason that dissolved additions via fertigation can include substances that influence pH/alkalinity and could be tested for that effect.

Says release of phosphorus from phosphate rocks to the soil exchange pool is very slow (occurs by erosion/weathering) and manufactured phosphate fertilizers come from phosphate rocks, implying raw rock phosphate is not rapidly available to plants.

A student could infer that because rock phosphate is slowly soluble, direct delivery via irrigation water (fertigation) may not provide immediately available P unless rock is processed or solubilized.

Defines phosphate-solubilizing microorganisms as biofertilizers used to increase availability of phosphorus by accelerating microbial processes.

A student could consider combining rock phosphate with phosphate-solubilizing microbes or inoculants in fertigation solutions to increase solubility and test whether this makes fertigation of rock phosphate effective.

States the need for more efficient, economic and integrated nutrient management systems combining organic, inorganic and biofertilizers to sustain productivity.

A student could view fertigation as one component of INM and design trials mixing rock phosphate with other nutrients or bioinputs in irrigation systems to evaluate efficiency versus conventional P fertilizers.

Notes that phosphates from fertilizers are easily leached from soils and can cause eutrophication when washed into water bodies.

A student should weigh the leaching/runoff risks of applying soluble P via irrigation; they could extend this to assess whether making rock phosphate more soluble for fertigation raises environmental loss risks.

States that manufactured fertilizers have high nutrient content and nutrients are released almost immediately, implying delivery method/timing affects when nutrients become available.

A student could reason that delivering such readily available nutrients through irrigation (fertigation) to the crop root zone may increase immediate availability compared with slow surface application.

Explains that in soil nutrients are held as ions on colloid surfaces and are the form readily available to plants, highlighting the importance of placing nutrients in ionic/soluble form near roots.

One could infer that dissolving fertilizers in irrigation water (creating soluble ions) could enhance the amount of nutrient in plant-available ionic form near roots.

Emphasises efficient nutrient management and combinations of sources to replenish soil nutrients and sustain productivity, linking method of application to efficiency.

A student might extend this to hypothesize that fertigation, as an efficient nutrient management practice, could improve nutrient use efficiency and availability compared with less targeted methods.

Advises restricting cultural operations so applied nutrients remain in the root zone and notes timing (after rains) affects fertilizer effectiveness, underscoring that placement/timing matter for availability.

Using a basic map of root zones and irrigation patterns, one could argue fertigation targets the root zone and can be timed to avoid losses, thereby increasing availability to plants.

Warns that excess fertilizers can be lost by leaching or runoff, indicating that application method influences how much nutrient remains available to plants versus lost to environment.

A student could infer that fertigation, by dosing nutrients with irrigation and potentially reducing surface runoff or timing to minimize leaching, might reduce losses and increase plant-available nutrients.

States that fertilizers contain major nutrients and that excess fertilizers may reach groundwater by leaching or enter surface waters by runoff.

A student could combine this with the basic fact that reducing the amount or improving placement/timing of applied fertilizer can reduce excess available for leaching, to assess whether fertigation (targeted delivery) might lower leaching.

Notes that industrial fertilizers have high nutrient content and that nutrients are released almost immediately.

A student could use the basic idea that immediate large releases increase the chance of leaching, and thus consider whether fertigation’s typically smaller/more frequent dosing could mitigate that risk.

Says excessive chemical fertilizers degrade soil structure and increase soil salts, implying soil condition influences nutrient retention and movement.

A student could combine this with knowledge that better soil structure and lower surface concentrations reduce percolation, and ask if fertigation practices help maintain soil structure or avoid salt buildup to reduce leaching.

Explains a mechanism (ion exchange in soil) by which nutrients like potassium and nitrate can be leached from soil.

A student could use this mechanistic rule and consider if fertigation’s timing/placement changes soil ion dynamics enough to reduce that exchange and subsequent leaching.

Recommends less use of chemical fertilizers to reduce nitrates in water bodies, linking application rate to downstream nutrient pollution.

A student could extend this by asking whether fertigation enables lower total fertilizer use (through efficiency), thereby reducing leaching and nitrate loading of water.