Soil testing in India needs to change the economics of a farmer’s decision

India’s rabi campaign can improve fertiliser use if it makes soil-based recommendations credible and economical to follow. The agriculture ministry’s 21 October announcement for Khet Bachao Abhiyan proposes soil testing, demonstrations, advice on balanced fertiliser use and water conservation. A recommendation may be agronomically sound and still go unused. The farmer has to trust it, obtain the recommended inputs before sowing and bear the loss if it performs poorly in their field. The campaign should therefore measure how farmers act on advice and how their returns change. Counting demonstrations or soil reports would establish how far the campaign reached, with little evidence on whether it improved decisions. Agriculture ministry’s rabi campaign announcement · Field experiment on soil recommendations in Bihar

A Bihar experiment clarifies what information can deliver

In a field experiment in Bihar, researchers gave farmers plot-specific fertiliser recommendations and measured their subsequent choices. They found little evidence of sizeable changes in fertiliser use overall. Responses were clearer for some low-cost recommendations and among farmers who were less confident in their own prior beliefs about suitable application rates. This is evidence from a particular intervention and region, not an estimate of the current campaign’s likely effect nationwide. It identifies a problem a broader campaign can test. Information can change choices where it is trusted and actionable. It may do little where the farmer already has a confident view or where inputs and credit are difficult to obtain. Field experiment on soil recommendations in Bihar · International Growth Centre’s study brief

A soil report is an input to a decision under uncertainty. Sampling and interpretation matter because soil can vary between plots and within a plot. A farmer who applied a familiar mix last year has direct experience of that practice, although yields also depended on weather and other inputs. The recommended change is less familiar. Even if it raises expected income, a household with limited savings may prefer a known practice to one with a greater perceived chance of a bad outcome. A well-documented demonstration can reduce uncertainty if the field and conditions are similar enough for the result to be relevant.

Profit and downside risk matter alongside yield

Suppose an illustrative one-hectare crop sells for ₹2,200 per quintal and the recommended input plan costs ₹1,100 more than the existing plan. With all other costs held fixed, the farmer needs an additional half-quintal of saleable crop to cover the added expense. A gain of one quintal increases gross margin by ₹1,100. If yield is unchanged, gross margin falls by ₹1,100. The price and costs are assumptions, not measured returns from a demonstration. They show why the campaign should report net returns and the spread of results, rather than a percentage yield gain by itself.

The arithmetic also runs in the other direction. Suppose a revised nutrient plan saves ₹1,100 and a farmer expects to sell at the same ₹2,200 per quintal. The saving would cover a yield decline of up to half a quintal per hectare under the same simplifying assumptions. Farmers need advice about which reduction is plausible for their fields and which input can be reduced without worsening a nutrient constraint. A uniform instruction to use less can impose costs where a nutrient is already underapplied. Plot-level recommendations should consider both the price paid by the farmer and any environmental or fiscal cost of excess use. Field experiment on soil recommendations in Bihar

Why a recommendation may be hard to implement

An input that is cheap on paper can be expensive to acquire if the dealer does not stock it, sells it only in larger packs or requires a trip to a distant market. If the test comes back after farmers have bought inputs, even a convincing recommendation may have to wait a season. A campaign should record the date of sampling, the date advice is available, what the farmer is advised to buy and whether that product is available nearby. Coordinating laboratories, extension staff and suppliers before the planting window could matter more than distributing additional reports late in the season. Agriculture ministry’s rabi campaign announcement · International Growth Centre’s study brief

There is also a tenancy and timing problem. A tenant with a short lease may be reluctant to pay for a change whose benefits accumulate in the soil over several years. A landowner may benefit from higher future productivity while the tenant bears the upfront cost. Practices with immediate input savings or a short payback are easier to adopt under those terms. For investments with longer returns, understanding who controls the plot next season and who captures the value is part of deciding how to support adoption. Demonstrations showing first-season results can be paired with longer observations where the effect is expected to accumulate.

Input subsidies can also make the private and public returns diverge. A farmer deciding whether to use one more bag responds to the price charged by the dealer and the crop they expect to harvest. The public cost can include part of the production or import cost and the effect of nutrient loss into water. Where testing identifies unnecessary use, a reduction can benefit the farmer and lower costs borne elsewhere. Where testing identifies a deficiency, additional use can raise production and farm income. A credible evaluation should allow for both directions and should avoid interpreting a national reduction in tonnes as the objective for every farm. Field experiment on soil recommendations in Bihar

The strongest case for broad outreach

A broad campaign can reach farmers who have never seen a reliable soil test or observed a different nutrient plan used locally. Extension staff can translate a technical result into a practical instruction and help groups share the fixed cost of testing and demonstrations. The research suggests that advice has value for some farmers, even when the average response is modest. The argument for expanding the programme is strongest where the same campaign can lower the cost of implementation or uncertainty about returns. Where neither constraint changes, additional outreach may improve awareness while leaving practices largely intact. Agriculture ministry’s rabi campaign announcement · Field experiment on soil recommendations in Bihar

Useful demonstrations should include a comparison plot or paired strips on the same field where feasible. Record seed, weather, irrigation, input quantities, labour, yield and sale prices, including cases where the new practice performs poorly. A comparison across nearby plots cannot remove every source of bias, but it can provide more relevant evidence than a single showcase farm with different conditions. Farmers should also be able to try the recommendation on a small area before committing an entire crop. That lowers the cost of learning and gives the programme a way to observe voluntary adoption after the first test.

Selection also affects the evidence from demonstrations. Hosts may have better irrigation, more reliable dealers or larger fields than the farmers the campaign most wants to reach. Comparisons should include groups with poorer access to inputs and credit. Tracking losses as well as gains matters because two recommendations with the same average return can have very different appeal to households unable to absorb a bad harvest. An observed decision to continue on a larger share of the plot next year can be informative when combined with measured returns.

What the next season should reveal

The government should look for advice delivered before purchases, adoption of the specific recommendation, net returns and whether adoption persists after demonstrations end. Distinguish higher input use recommended for deficient fields from lower use where inputs were being wasted. Compare results by crop, access to irrigation, tenancy and availability of the recommended products. If growers adopt the practices and see better margins or more reliable output, the next round can focus on scaling what worked. If adoption remains low despite timely and credible advice, the evidence should direct attention to input availability, risk or the terms on which farmers can finance a change. Agriculture ministry’s rabi campaign announcement · Field experiment on soil recommendations in Bihar