Agricultural Land: How to Evaluate Soil, Water and Crop Suitability

Five factors that determine agricultural land productivity

Agricultural land suitability is not binary. It is a gradient that varies by target crop, production system and input level available. The five site-specific factors that determine whether a parcel is productive for a given crop are:

1. Soil: texture, effective depth, pH, organic matter, internal drainage. No amount of inputs can overcome a soil that structurally limits rooting depth or drains poorly.
2. Water: rainfall regime — mean and drought-year distribution — plus access to irrigation and aquifer status if irrigation is planned.
3. Climate: temperature range, frost-free window, heat accumulation, drought frequency and severity.
4. Flood risk: percentage of the parcel that floods in wet years, frequency and duration. This is the most commonly omitted factor in standard land transactions.
5. Logistics: distance to storage, processing and market. For low-value-density crops (sorghum, maize), freight can consume 30-50% of margin.

None of these five appear in a standard land title or sales listing. All are verifiable before purchase.

Soil depth: the single most important physical characteristic

Effective soil depth — the depth to which roots can penetrate without restriction — determines yield ceiling more than any other single factor. A loam soil with 1.2m effective depth can store roughly 160-200mm of plant-available water. The same loam over a hard pan at 40cm stores less than 60mm. In a dry year with 15-20 dry days during grain fill, the first soil supports the crop; the second one doesn't.

Minimum effective depths for common field crops: maize and soybean need at least 60-80cm. Alfalfa requires 100cm+ for multi-year root development. Wheat and sorghum are more tolerant but still benefit from 60cm+ for drought resilience.

Rainfall: average vs. drought year

Annual average rainfall is the most widely cited climate metric for agricultural land. It is also the least useful for investment-grade evaluation. The relevant parameters are:

• Drought-year rainfall (p10): how much falls in the driest year that occurs roughly once per decade. This is the floor of production to plan for.
• Intra-seasonal distribution: whether rainfall arrives in the critical windows for the target crop — germination, flowering, grain fill. A 600mm annual total concentrated in 60 days can be worse for maize than 450mm distributed across 4 months.
• Frequency of total crop failure: how often the drought year falls in a critical stage. In highly variable climates, this can be every 4-5 years.

Rainfed agricultural land in a zone with 650mm average but drought years of 300mm every 5-6 years has a very different risk profile from land with 550mm stable. The second may be more valuable to a buyer projecting over a 10-year horizon.

Flood risk: the most commonly omitted factor

Flood history on a specific cadastral parcel is almost never mentioned in a standard land sales description — and it is one of the most consequential factors for agricultural land profitability. A parcel that floods 15% of its area in wet years loses that proportion as direct crop loss, plus additional losses from soil compaction and delayed planting when the field is worked wet.

Satellite-based records from JRC Global Surface Water cover the last 30 years at parcel level. They show exactly which portions of a cadastral polygon have been inundated in each year, and with what frequency. This information is not routinely disclosed by sellers. It needs to be actively sought.

Crop suitability reference by rainfall regime