Sustainable Fertilizers in a Changing Climate: Can Farmers Balance Yield, Cost and Carbon?

Fertilizers remain one of agriculture's most powerful productivity levers – and one of its most exposed cost and emissions lines. Nitrogen starts with ammonia, whose production accounted for roughly 2% of global final energy consumption and about 1.3% (≈450 Mt) of energy-system CO₂ emissions in 2020; around 70% of ammonia is used to make fertilizers [1]. Across manufacture, transport and field nitrous oxide (N₂O), the synthetic-nitrogen supply chain was estimated at 1.13 Gt CO₂e in 2018, about 2.1% of global greenhouse-gas emissions (global, modelled estimate) [2].

Price exposure is equally material. The World Bank's April 2026 Commodity Markets Outlook projected its fertilizer price index to rise by about 31% in 2026, led by urea, after Middle East shipping disruptions, and noted that natural gas accounts for 80–90% of ammonia production cost (global; forecast, not outturn) [5]. Meanwhile, organic farmland held broadly stable at 98.9 million ha in 2024 – about 2.1% of global agricultural land – while organic retail sales reached roughly €145 billion (global; reported) [6]. Soil-health programmes, food companies' Scope 3 targets and a changing climate – which can alter nutrient losses through leaching, volatilisation and denitrification, and shift the timing of crop uptake – add further pressure.

The question is therefore no longer “organic or chemical?” It is whether farmers can adopt more sustainable fertilizer strategies without compromising productivity or significantly raising costs, while also reducing carbon intensity. We frame this as The New Fertilizer Equation (Figure 1): yield, cost, nutrient efficiency, carbon and soil health evaluated together – per tonne of crop produced, not per tonne of fertilizer bought. The answer increasingly points to a portfolio of nutrient sources rather than a binary choice.

Figure 1. The New Fertilizer Equation and the sustainable fertilizer spectrum. Conceptual framework; contains no quantitative data.

“Sustainable fertilizer” is not one product class. It spans organic manures and composts, biofertilizers, recycled or circular nutrients (e.g., digestates, recovered struvite), naturally mined minerals, enhanced-efficiency fertilizers (inhibitor-treated or coated products), low-carbon fertilizers (e.g., ammonia with carbon capture) and green-ammonia-based nitrogen. These categories overlap: a mined sulfate mineral can be both natural and low-energy; green-ammonia urea can be applied in an enhanced-efficiency formulation. Sustainability is a property of how a nutrient is produced, matched and applied – not of its label alone.

Evaporite and sedimentary deposits supply several naturally sourced nutrient materials with distinct chemistry (Table 1). Polyhalite (K₂Ca₂Mg(SO₄)₄·2H₂O), mined in North Yorkshire and marketed as ICL Polysulphate and Anglo American POLY4, is primarily a sulfur source that also supplies K, Mg and Ca [11]. Langbeinite (K₂SO₄·2MgSO₄) supplies K, Mg and S; K-Mag and Sul-Po-Mag are commercial names for langbeinite-type products, but grades differ in guarantee, particle size and solubility and should not be treated as identical [12]. Korn-KALI and PatentKALI (K+S) are processed potash–magnesium fertilizers rather than single raw minerals: Korn-KALI is chloride-based with kieserite, PatentKALI is sulfate-based [13]. Kainite is a crude potash salt rich in sodium and chloride, suited to grassland and sugar beet but not to chloride-sensitive crops. Rock phosphate, greensand (glauconite) and gypsum are slower or narrower sources: rock phosphate carries substantial total P₂O₅ but low immediate availability, especially in neutral-to-alkaline soils; greensand's potassium is largely non-water-soluble; gypsum supplies Ca and S without raising soil pH [14].

Labels conventionally report nutrients as oxides (P₂O₅, K₂O, MgO, SO₃, CaO). Elemental contents are lower: K = 0.830 × K₂O; P = 0.436 × P₂O₅; Mg = 0.603 × MgO; S = 0.400 × SO₃; Ca = 0.715 × CaO. Polyhalite's 14% K₂O, 6% MgO, 48% SO₃ and 17% CaO, for instance, equal about 11.6% K, 3.6% Mg, 19.2% S and 12.2% Ca. Comparisons across products – and against crop removal – must use one consistent basis; elemental equivalents for all products are provided in the accompanying Excel file.

Table 1. Nutrient composition of selected natural mineral and multi-nutrient fertilizers (% by weight, oxide basis). Sourced data from manufacturer specifications and university extension references [11–14]; values are declared/typical and not independently tested. Ranges reflect different grades, markets or deposits; “theoretical” rows are calculated from mineral formulae; “≈” values are converted from elemental guarantees. Verify current specifications before use.

Each nutrient performs distinct functions (Figure 2A). Nitrogen drives vegetative growth, protein formation and biomass. Phosphorus supports root development, energy transfer (ATP) and reproductive development. Potassium regulates water relations and osmotic balance, underpinning stress tolerance and crop quality. Among secondary nutrients, magnesium is the central atom of chlorophyll and activates enzymes in photosynthesis; sulfur is a constituent of the amino acids cysteine and methionine, essential for protein synthesis and closely linked to nitrogen-use efficiency and to oil and protein quality in oilseeds and pulses; calcium builds cell walls and root and tissue structure and is largely immobile within the plant.

Secondary nutrients matter more as intensive, NPK-focused systems draw them down. In India, ICAR coordinated-project data reported to Parliament indicated that about 41% of soils were sulfur-deficient (national survey data, reported 2005) [16]; the Soil Health Card scheme now tests S alongside N, P and K and promotes balanced, integrated nutrient management [16]. Three distinctions matter when evaluating any product: nutrient supply (what the analysis contains), agronomic potential (whether those nutrients are limiting on a given field) and demonstrated field performance (replicated results under defined conditions). A product can supply a nutrient the crop does not need, and one positive trial does not establish a universal benefit.

Why multi-nutrient fertilizers matter

Multi-nutrient fertilizers combine several nutrients in one granule, which can simplify blending, reduce application passes and distribute low-rate secondary nutrients evenly. Where soils are deficient in more than one nutrient, supplying them together can relieve constraints that otherwise cap the return on nitrogen – sulfur deficiency, for example, limits the crop's use of applied N. Low-chloride sulfate forms are also relevant for chloride-sensitive crops such as potatoes, tobacco, fruit and many vegetables. Crop-specific formulation and logistics (one product, one supply chain) add operational value.

Polyhalite illustrates both promise and caveats (Figure 2B). Field studies at ICAR-IARI, New Delhi, reported higher agronomic efficiency, grain K and root growth when polyhalite replaced muriate of potash (MOP) as the K source in wheat in 2021–22 [15] – demonstrated performance under specific conditions, not a general yield guarantee. The trade-off is concentration: at 14% K₂O, polyhalite supplies far less K per tonne than MOP (≈60% K₂O), so its value depends on whether the accompanying S, Mg and Ca are agronomically needed and on delivered cost per unit of useful nutrient, including freight.

Figure 2. N–P–K–Mg–S–Ca nutrient functions and the multi-nutrient pathway. Conceptual; functions summarise established plant physiology. The pathway does not imply a guaranteed yield response, which is site- and crop-specific.

Interest is rising across organic, regenerative and broader sustainable systems, with shared emphases on soil organic matter, biological nutrient cycling, biofertilizers, nutrient recycling, natural minerals and, increasingly, precision application. Relying exclusively on low-concentration organic sources, however, raises practical constraints: nutrient concentrations are low and variable, so large tonnages must be transported and spread; release depends on microbial mineralisation, which may not coincide with peak crop demand; product consistency varies; and the scale of nutrient demand in high-yield systems can exceed locally available organic material.

The yield evidence is context-specific. A meta-analysis of 115 studies found organic yields on average about 19% lower than conventional, narrowing to roughly 8–9% where crop rotations or multi-cropping were used [7]; an earlier meta-analysis reported gaps from about 5% to 34% depending on crop and conditions [8]. Neither “organic always yields less” nor “organic always yields more” is supported; outcomes vary by crop, geography, soil and management. This motivates Integrated Nutrient Management (INM) (Figure 3): organic inputs + biofertilizers + natural minerals + efficient mineral fertilizers + precision application, guided by soil tests. India has long promoted INM through ICAR packages and soil-test-based recommendations [16]. We treat INM as an analytical framework – the right mix depends on soil, crop, climate, certification and farm economics – not as a universal prescription.

Figure 3. Integrated nutrient management framework. Conceptual framework; contains no quantitative data.

Three dimensions interact. Yield determines productivity and food security; cost determines farm margins; carbon captures embodied and supply-chain emissions from fertilizer manufacture, transport and field use. Nutrient-use efficiency (NUE) links them: global cropland nitrogen-use efficiency has been estimated at about 0.4 – more than half of applied N is not recovered in harvested crops – and would need to rise to roughly 0.7 by 2050 to meet food and environmental goals [4]. Life-cycle analysis suggests about two-thirds of nitrogen-fertilizer emissions occur after application, making efficiency the single most effective lever, alongside decarbonised production [3]. Two ratios reframe the decision:

The cheapest fertilizer per tonne does not necessarily deliver the lowest cost per tonne of crop: a cheaper product that leaves a nutrient limiting, or is lost before uptake, raises cost per unit of output. These ratios are deliberately simple. They exclude application labour and machinery, multi-season soil-fertility and residual effects, price risk and quality premiums, and the emissions boundary (cradle-to-gate versus including field N₂O) must always be stated.

We compare three illustrative scenarios for a sample cereal hectare (Figure 4; Table 2). Cost-first agriculture: conventional fertilizers remain competitive, carbon costs are limited and farmers optimise near-term economics. Carbon-constrained agriculture: carbon accounting matters, buyers reward lower-carbon inputs and low-carbon nitrogen gains commercial relevance at a premium. Integrated sustainable nutrient management: organic inputs, natural minerals, biofertilizers, enhanced-efficiency products, precision application and soil-health practices are combined.

Under the sample assumptions (fertilizer cost USD 250/310/280 per ha; yield 6.0/6.0/5.9 t/ha; fertilizer-related emissions 1.6/1.0/1.2 t CO₂e/ha), the cost-first case has the lowest fertilizer cost per tonne of crop (USD 41.7/t) but the highest fertilizer-related carbon intensity (0.27 t CO₂e/t). The carbon-constrained case cuts carbon intensity by 37.5% at a 24% cost premium; the integrated case sits between them, with a slightly lower sample yield. Applying a carbon value changes the ranking (Figure 4B): at zero, cost-first is cheapest; near USD 100/t CO₂e the three converge; above that, lower-carbon strategies become cheaper on a carbon-adjusted basis. The crossover point is an artefact of sample data – the insight is that rankings are sensitive to yield, NUE and the carbon value assumed.

Table 2. Qualitative comparison of fertilizer scenarios. Qualitative analytical assessment; no numerical values are implied.

Figure 4. Illustrative Yield–Cost–Carbon comparison and scenario-based fertilizer economics. Data are sample and illustrative and are intended to demonstrate the analytical framework; they do not represent actual market values unless explicitly sourced. Assumptions in the Excel file.

Credible, public and consistently defined estimates of the multi-nutrient or natural-mineral fertilizer market are scarce; commercial estimates vary widely in product definition and are often proprietary, so we assess market scope qualitatively rather than citing a figure.

Conventional ammonia is made by Haber–Bosch synthesis using hydrogen from natural-gas reforming or coal gasification; the global average energy intensity is about 41 GJ/t (net) versus best-available-technology levels of 28 GJ/t for gas-based plants [1]. Green ammonia replaces fossil hydrogen with electrolytic hydrogen from renewable power (Figure 5A), removing most direct process CO₂; each tonne of ammonia needs roughly 0.18 t of hydrogen (stoichiometric). Economics are dominated by renewable electricity cost, electrolyser capex and utilisation, and the cost of capital. The IEA reports that, depending on location, renewable hydrogen costs roughly 1.5–7 times more than unabated fossil hydrogen, and low-emissions hydrogen remains under 1% of global hydrogen demand (global, 2024 data) [9]. Policy can narrow the gap: the EU CBAM entered its definitive phase for imported fertilizers on 1 January 2026, with the first certificate surrender for 2026 imports due by 30 September 2027 [10].

The key distinction: lower-carbon production does not automatically mean lower fertilizer cost for the farmer. The delivered price depends on energy prices, production efficiency, the prevailing fertilizer market price, the carbon value captured (through regulation or buyer premiums), logistics and policy support. During a gas-price spike, low-carbon nitrogen backed by contracted renewable power can look relatively competitive; when gas is cheap, the premium widens. Field N₂O emissions are also unaffected by how ammonia is made, so production decarbonisation must be paired with efficiency.

Figure 5. Green H₂ → green NH₃ → fertilizer value chain, and the shift to carbon-aware procurement. Conceptual diagrams; contain no quantitative data.

Procurement has traditionally weighed price, quality and availability. An emerging approach adds carbon intensity and supply risk (Figure 5B). We call this Carbon-Adjusted Fertilizer Economics:

The carbon value may be a regulatory price (e.g., CBAM exposure for EU importers), an internal carbon price, or a buyer premium tied to Scope 3 targets. This is an analytical framework, not a description of current universal practice – most farm-level purchasing remains price-led. Its value lies in making hidden exposures visible: the same tonne of nitrogen can carry very different embedded emissions and supply risks depending on origin and production route, and Figure 4B shows how rankings shift as the carbon value rises.

For 2030–2035 we expect multiple fertilizer pathways rather than a single replacement technology. Table 3 sets out qualitative Low, Base and High transition cases – scenarios, not forecasts. In all three, conventional nitrogen remains the backbone of global supply; the open questions are how quickly nutrient-use efficiency improves, how much low-carbon ammonia reaches commercial scale, and how far carbon values reach into farm-gate prices. Natural mineral and multi-nutrient fertilizers are likely to grow where secondary-nutrient deficiencies, chloride sensitivity or organic certification create a clear agronomic case, and to remain niche where they do not. Organic and biological inputs will expand alongside, rather than instead of, mineral nutrition in most high-yield systems. The advantage will go to those who manage the portfolio: matching nutrient source to soil and crop, measuring cost and carbon per tonne of output, and stress-testing decisions against energy, carbon, policy and trade scenarios.

Table 3. 2030–2035 sustainable fertilizer outlook: qualitative Low / Base / High transition cases. Qualitative scenario framework developed for this article; not a forecast and contains no market values.

Navigating the new fertilizer economy

Sustainable fertilizer decisions now sit at the intersection of commodity prices, energy markets, carbon policy, agronomy and supply chains. EnviroSUSIQ helps businesses analyse these interactions through:

Whether you are a producer assessing low-carbon capacity, a distributor building a multi-nutrient portfolio or a food company managing Scope 3 exposure, the objective is the same: understand how alternative production pathways, carbon values and market conditions shape cost and risk per tonne of output.

Visit EnviroSUSIQ to explore its decarbonisation and commodity analytics capabilities.