Effective Methods for Applying Manures and Fertilizers

Getting nutrients to your horticultural crops isn’t just about what you apply – it’s fundamentally about how you apply it. Even the best fertilizer or well-composted manure can underperform if delivered using the wrong method for the crop, soil, or growth stage. From simply scattering granules across a field to injecting dissolved nutrients directly into drip irrigation lines, each application method has a distinct logic behind it. Understanding these methods helps growers make smarter decisions that improve yields, cut input waste, and reduce environmental impact.

Why the method of application matters 🔗

Plants can only absorb what reaches their roots or leaves in an available form. A large portion of soil-applied fertilizer never actually reaches the plant – lost to runoff, leaching, or chemical fixation in the soil. Research on vegetable crop nutrition confirms that fertilizers are applied in solid form in about 90% of cases, with liquid methods making up the remaining 10%. Both solid and liquid forms come with their own set of application techniques, each suited to specific situations.

Solid fertilizer application methods 🔗

Broadcasting 🔗

Broadcasting is the most straightforward approach – fertilizer or manure is spread uniformly across the entire field surface. According to Tamil Nadu Agricultural University (TNAU), this method is best suited to crops with a dense stand where plant roots permeate the whole soil volume, or when large quantities of relatively insoluble fertilizers like rock phosphate need to be applied.

Broadcasting is done in two ways. Basal application (broadcasting at sowing or planting) distributes fertilizer evenly across the field before or at the time of sowing, mixing it into the soil. Top dressing, on the other hand, applies fertilizers – particularly nitrogenous ones – to standing crops without incorporation. It is widely used in closely sown crops like leafy vegetables, paddy, and wheat to supply nitrogen in a readily available form during active growth.

The main drawback of broadcasting is efficiency loss. Nutrients spread across the entire field surface can be taken up by weeds, fixed by soil contact before reaching plant roots, or lost through runoff. Cropnuts notes that proper equipment calibration is essential with this method to avoid uneven distribution.

Placement methods 🔗

Placement involves applying fertilizer at a specific location relative to the seed or plant, rather than across the whole field. TNAU identifies placement as the preferred approach when fertilizer quantities are small, root development is limited, or when phosphatic and potassic fertilizers need protection from soil fixation.

Key placement methods include:

• Band placement – Fertilizer is placed in narrow bands on one or both sides of the plant row. In orchards (mango, apple, grapes, papaya), this is done as hill placement around the base of the tree. For row crops like sugarcane, potato, and maize, it is done as row placement in continuous bands alongside the rows.
• Side dressing – Fertilizer is applied in between crop rows or around individual plants during the growing season. It is especially common for supplying additional nitrogen to crops like maize and sugarcane.
• Plough sole placement – Fertilizer is placed at the bottom of the plough furrow during tillage, then covered as the next furrow is turned. This method suits areas where the surface soil dries out quickly.
• Deep placement – Used specifically in paddy fields to place ammoniacal nitrogen in the reduction zone of the soil, where it stays available longer and is protected from runoff losses.

The advantages of placement over broadcasting are significant. OER Commons explains that banding fertilizer reduces the risk of it contacting foliage, slows the conversion of ammonium to nitrate (reducing leaching risk), and creates a concentrated nutrient zone that is easy for developing roots to access. Weed growth is also reduced since nutrients are not distributed across the entire field surface.

Liquid fertilizer application methods 🔗

Starter solutions 🔗

Starter solutions are dilute liquid fertilizers applied directly to young seedlings at the time of transplanting – most commonly for vegetable crops. TNAU describes the standard ratio as N:P₂O₅:K₂O in proportions of 1:2:1 or 1:1:2. The primary goal is to encourage rapid root establishment and early shoot growth. The high phosphorus component supports root development in the critical first days after transplanting. The limitation is that extra labour is required, and phosphate fixation in the soil can still reduce efficiency.

Foliar application 🔗

Foliar application means spraying a dissolved fertilizer solution directly onto the leaves of growing plants. Leaves absorb nutrients through their surface, particularly via stomata and cuticle pores, and nutrients are then translocated through the plant. ScienceDirect notes that foliar fertilization typically meets only about 10% of total plant nutritional needs unless applied repeatedly – it is a supplementary technique, not a primary one.

Where foliar application truly excels is in delivering micronutrients. Elements like iron, zinc, copper, boron, and manganese are frequently unavailable to roots in high-pH or waterlogged soils, making soil application ineffective. UConn’s Soil Nutrient Analysis Laboratory recommends foliar feeding primarily for correcting specific micronutrient deficiencies, noting its speed of action as a key advantage. Research published in Scientific Reports found that multi-element foliar fertilization of eggplant significantly increased fruit concentrations of iron, zinc, copper, and manganese – all critical for both plant health and produce nutritional quality.

Timing and concentration are critical. Spraying should be done in the early morning or evening when temperatures are below 22°C. High concentrations can scorch leaves and damage the crop. For this reason, frequent low-concentration applications are preferred over infrequent heavy ones.

Fertigation 🔗

Fertigation – the delivery of water-soluble fertilizers through the irrigation system – is widely considered the most efficient nutrient application method available for high-value horticultural crops. Wikipedia’s overview of fertigation defines it as the injection of fertilizers into an irrigation system, with the nutrients carried directly into the soil in solution and delivered to the root zone.

Fertigation can be applied through drip, furrow, or sprinkler systems, but drip irrigation is generally the most effective delivery mechanism. A comprehensive review published in Plant Science Today explains that drip fertigation delivers precise amounts of water and nutrients directly to the root zone, optimising both water and nutrient use efficiency, reducing losses from leaching and runoff, and supporting better crop growth through controlled, stage-specific nutrition.

The efficiency gains are substantial. A study published in Frontiers in Sustainable Food Systems found that optimised fertigation techniques can reduce nitrate leaching to as little as 7.1% while increasing plant uptake to 73.5% – a dramatic improvement over conventional fertilization where much of the applied nutrient never reaches the crop. Farmers can save 15-25% on fertilizer costs through drip fertigation, according to a chapter in Sustainable Agriculture Systems and Technologies (Wiley).

Research in the journal Horticulturae (MDPI) highlights that matching the fertilizer injection schedule to the crop’s actual nutrient uptake rate at each growth stage is the key principle behind effective fertigation management. Most horticultural crops – vegetables, fruit trees, and ornamentals – have distinct phases of high nutrient demand, and fertigation allows growers to align nutrient supply precisely with those phases.

Injection into soil and aerial application 🔗

Two less common liquid methods round out the picture. Soil injection involves placing liquid fertilizers directly into the soil using pressure or non-pressure systems. Anhydrous ammonia – the only gaseous fertilizer in common use – must be injected 12-15 cm deep and immediately covered to prevent nitrogen loss through volatilisation. Studies cited by OER Commons indicate that placing manure below the soil surface can reduce ammonia losses by up to 100% compared to surface application. Aerial application by aircraft is reserved for situations where ground access is impractical – hilly terrain, forest land, sugarcane fields, and grasslands – where conventional equipment cannot operate.

Choosing the right method for your crop 🔗

No single application method is universally best. The right choice depends on crop type, growth stage, available equipment, soil conditions, and the nutrient being applied. Oregon State University’s College of Agricultural Sciences emphasises that soil and tissue testing should always inform fertilizer decisions, so that the method chosen matches the plant’s actual needs rather than a generic schedule.

For large-scale leafy vegetables or grain crops in dense stands, broadcasting remains practical and cost-effective. For orchards and widely spaced perennial fruit crops, band or circular placement around the root zone is more targeted. For transplanted vegetables, starter solutions give seedlings the initial boost they need. During critical growth stages when micronutrient deficiencies appear, foliar sprays offer a fast and precise correction. And for high-value horticultural crops under drip irrigation – tomatoes, peppers, cucumbers, strawberries – fertigation delivers the highest return on every unit of fertilizer applied.

Van Iperen International captures the governing principle well: the ultimate goal of any fertilizer application method is to optimise crop nutrition while minimising environmental impact. Combining methods strategically – such as basal broadcasting at establishment, side dressing during vegetative growth, and foliar correction for micronutrients – gives growers precise control over nutrition across the entire crop cycle.

What do you think? Given that fertigation consistently outperforms conventional methods in nutrient use efficiency, what practical or economic barriers might prevent smallholder horticultural growers from adopting it – and how might those barriers be addressed? And when managing a mixed orchard with both young transplants and mature fruit trees, how would you design a combined application strategy that accounts for the different nutrient demands at each stage?

References

1. https://www.researchgate.net/publication/372956902_Manures_and_fertilizers_application_in_vegetable_crops
2. http://www.agritech.tnau.ac.in/agriculture/agri_nutrientmgt_methodsoffertilizerappln.html
3. https://cropnuts.com/fertilizer-application-techniques/
4. https://oercommons.org/courseware/lesson/87608/overview
5. https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/foliar-application
6. https://soiltesting.cahnr.uconn.edu/foliar-fertilization/
7. https://www.nature.com/articles/s41598-022-09247-0
8. https://en.wikipedia.org/wiki/Fertigation
9. https://horizonepublishing.com/journals/index.php/PST/article/view/10298
10. https://www.frontiersin.org/journals/sustainable-food-systems/articles/10.3389/fsufs.2024.1494819/full
11. https://onlinelibrary.wiley.com/doi/abs/10.1002/9781119808565.ch12
12. https://www.mdpi.com/2311-7524/3/2/37
13. https://agsci.oregonstate.edu/mes/sustainable-onion-production/best-management-practices-fertilization
14. https://www.vaniperen.com/story/methods-of-fertilizers-application/