Organic fertilizer helped maize—but wheat needed a different plan

A regional meta-analysis shows why organic fertilizer substitution depends on crop, soil and nutrient-release timing.

This SoilBeat article draws on research by Yi Wang, Lu Li, Zihao Liu and colleagues, published in BMC Plant Biology. The study findings are theirs; the practical interpretation below is SoilBeat’s. Read the original research.

Replacing part of a mineral-fertilizer program with organic fertilizer sounds like a single agronomic decision. In practice, it is several decisions hidden inside one label.

What material is being used? How much of its nitrogen is mineral and immediately available? How quickly will its organic N mineralize? Is the soil warm and moist enough for microbial release? Can phosphorus diffuse to roots in that soil? Does the crop need nutrients early, or can it wait for later mineralization?

A regional meta-analysis makes the consequences visible. In China’s Huang-Huai-Hai Plain, organic fertilizer substitution produced a positive average maize response, no significant overall wheat response, and a negative yield response in neutral soils. The paper’s practical value is not a universal substitution percentage. It is the warning that crop, soil, and nutrient-release timing can reverse the result.

Research finding

Researchers synthesized 73 open-field studies containing 541 paired observations from winter wheat–summer maize systems. Of those effect sizes, 270 represented maize and 271 wheat.

The literature search covered Web of Science and the China National Knowledge Infrastructure through the end of 2025. Eligible experiments compared organic fertilizer alone or organic–mineral combinations with chemical-fertilizer controls and reported means, replication, and variability. The authors used random-effects meta-analysis and subgrouped results by crop, soil texture, soil type, and initial pH.

Across the maize dataset, substitution increased yield by 16.45% on average. Wheat yield did not change significantly overall.

Source: Yi Wang, Lu Li, Zihao Liu and colleagues (BMC Plant Biology, 2026)

The soil context mattered:

• Maize yield increased 16.45% in loam and 4.44% in clay.

• Fluvo-aquic soils showed a 22.09% maize increase.

• Alkaline soils with initial pH at or above 7.5 showed a 20.39% increase.

• Neutral soils between pH 6.5 and 7.5 showed a 7.26% yield decrease.

• Wheat had only modest significant gains in selected soil groups: 3.40% in brown soil, 2.51% in cinnamon soil, and 2.55% under alkaline conditions.

Soil indicators generally improved. Organic matter increased by about 10% in both clay and loam. Available phosphorus increased 20.01% in loam, 30.55% in fluvo-aquic soil, and 23.74% in alkaline soil. Total N increased 5.52% in clay and 13.09% in loam. Nitrate-reductase activity increased 64.01% in loam and fluvo-aquic soils and 70.90% under alkaline conditions.

Those changes are agronomically useful, but they did not translate into the same yield response everywhere.

Agronomic interpretation

Organic fertilizers contain nutrients in different chemical forms and release them at different rates. A soluble mineral-N fraction can enter the ammonium and nitrate pools quickly. Organic N must first be decomposed and mineralized by microbes. That process depends on material composition, carbon-to-nitrogen ratio, particle size, placement, temperature, moisture, aeration, and microbial activity.

Summer maize grows during warmer conditions that generally favor mineralization. Its high nutrient demand can overlap better with nutrient release from organic inputs. Winter wheat establishes under cooler conditions, when slow mineralization can leave less plant-available N during early tillering and canopy formation. That timing mismatch is a plausible explanation for the crop contrast, but the meta-analysis did not directly track nutrient release or roots across every study.

Texture changes the same process. Loam can provide a favorable balance among water retention, aeration, root exploration, and microbial activity. Clay can protect organic matter and nutrients on mineral surfaces, but diffusion, aeration, and physical access vary. The smaller average maize response in clay does not mean organic inputs are ineffective there; it means the yield response was more constrained or heterogeneous.

pH governs nutrient solubility and biology. In alkaline soil, added organic matter can increase microbial activity, contribute chelating compounds, and sometimes improve micronutrient and phosphorus availability. The synthesis reported bidirectional pH buffering: amendments tended to move acidic and alkaline soils toward less extreme values.

Yet neutral soil produced a negative maize response. That is important because neutral pH is often treated as inherently favorable. One possibility is that higher substitution reduced immediately available nutrients without a compensating pH benefit. Immobilization, amendment quality, or timing may also matter. The synthesis cannot identify one cause.

Why the average needs restraint

The 16.45% maize figure is attention-grabbing, but it is not a guaranteed response.

The maize funnel plot was strongly asymmetric, and Egger’s test indicated publication bias. Positive results may be overrepresented, small-study effects may be present, or study conditions may differ systematically. The wheat subset did not show the same signal.

The analysis also combined different organic materials and substitution strategies. Manure, compost, processed products, and crop-derived amendments do not share the same nutrient analysis, carbon chemistry, salinity, pathogen risk, or release curve. A tonne is not a nutrient-equivalent unit.

Where studies did not report standard deviations, the reviewers estimated them as one-tenth of the mean. That increases uncertainty around study weights. When several depths were reported, only the uppermost soil layer was used, so deeper nitrate movement and subsoil supply were not characterized consistently.

Finally, the study synthesized yield, soil chemistry, nutrient uptake, and enzyme indicators. It did not calculate a standardized margin, measure environmental losses under one common protocol, or prove that enzyme changes caused yield changes.

Possible management implication

Organic substitution should be designed as a nutrient-budget and release-timing decision.

Before changing a program, analyze the amendment for dry matter, total N, ammonium N, P, K, carbon-to-nitrogen ratio, pH, and electrical conductivity. Use realistic first-season availability coefficients rather than crediting total nutrients as immediately plant-available. Account for mineral fertilizer retained in the program, residual soil supply, irrigation or rainfall, and crop-stage demand.

For wheat, protect early nutrient availability. A substitution program that relies heavily on slow mineralization can miss the crop’s early demand even if total N looks adequate on paper. For maize, warm-season mineralization may improve synchrony, but drought or waterlogging can still interrupt microbial release and root uptake.

Monitor the crop, not just the application. Pre-plant and in-season mineral N, soil moisture and temperature, plant tissue or sap trends, biomass, and visual root-zone observations can distinguish delayed availability from insufficient total supply. Harvest measurements should include yield, nutrient removal, grain quality, residual nutrients, and a partial budget.

Recommendation

Do not copy the meta-analysis average into a fertilizer rate.

Where organic substitution is being considered, run replicated strips that compare the current mineral program with a nutrient-accounted organic–mineral program at the same realistic available-N target. If risk and evidence allow, include a responsibly reduced-mineral-N treatment. Keep cultivar, plant population, P and K balance, irrigation, and crop protection consistent enough to interpret the result.

Use the Measure → interpret → recommend → act → monitor loop: measure the amendment and soil supply; interpret release against crop stage, pH, texture, moisture, and temperature; recommend a locally testable nutrient budget; act in replicated strips; and monitor crop status, yield, residual fertility, losses where possible, and margin.

The value of an organic input is not its total nutrient content. It is the amount released in the root zone when that particular crop can use it.

References

Yi Wang, Lu Li, Zihao Liu and colleagues (2026). Contrasting responses of wheat and maize to organic fertilizer substitution in the Huang-Huai-Hai Plain: a meta-analysis. BMC Plant Biology.

AI-generated editorial illustration for SoilBeat. Conceptual imagery; not a photograph or figure from the study.