Intercrop Competition & Find Who Wins

LER (Land Equivalent Ratio) tells you whether the intercrop is more productive than sole crops overall — it is the sum of each component's partial LER (intercrop yield ÷ sole yield), and a value above 1 means a yield advantage. Aggressivity tells you which component is winning the competition: Aab = (Ya ÷ (Sa·Za)) − (Yb ÷ (Sb·Zb)). LER answers 'is it worth it', aggressivity answers 'who is dominating'.

If aggressivity (Aab) is positive, component A is the dominant, more competitive crop; if negative, component B dominates; near zero, the two are evenly matched. The further from zero, the stronger the imbalance. The tool flags A or B as dominant when the magnitude exceeds 0.1 and recommends shifting the row ratio toward the suppressed component.

The competitive ratio (CR) refines aggressivity by accounting for the sown proportions: CRa = (La ÷ Lb) × (Zb ÷ Za). A CRa above 1 means component A is more competitive per unit area sown than B. Unlike aggressivity, CR is a ratio, so it is easy to say 'A is 1.8 times as competitive as B'. The dominant crop has CR above 1 and the suppressed crop below 1.

The relative crowding coefficient (K), from de Wit, measures how much a component crowds out its partner relative to itself. Kab = (Ya·Zb) ÷ ((Sa−Ya)·Za). If a component's K is above 1 it produced more than expected in the mixture; the product K = Kab × Kba above 1 indicates a yield advantage from the combination, consistent with LER above 1.

AYL compares each component's intercrop yield per unit area it occupied against its sole yield: AYLa = (Ya ÷ Za) ÷ Sa − 1. A positive AYL means that component actually yielded more per unit of its land than as a sole crop; negative means it lost. The total AYL sums both and shows the net behaviour of the system beyond the simple LER.

The row ratio sets the sown proportions Za and Zb. A 2:1 maize-to-pigeonpea stand gives Za = 0.667 and Zb = 0.333. These proportions appear in aggressivity, competitive ratio, crowding and actual yield loss, because each index asks how a component performed relative to the share of land it was given. Change the ratio and every competition index changes.

Usually yes, if the goal is a balanced harvest of both crops. When one component is strongly dominant, reducing its rows or adding rows of the suppressed crop re-balances the stand and often raises the total LER by letting the weaker crop contribute more. If you only want the dominant crop and the legume is a bonus, you may keep the ratio — the tool's recommendation assumes you value both.

It means you would need more than one hectare of sole crops to produce what the intercrop produces on one hectare. An LER of 1.3 means a 30 percent land-use advantage — the same yields would need 1.3 ha as monocultures. This is the classic justification for intercropping, and it usually comes from the two crops using light, water and nutrients at different times or depths.

The tool includes ten reference pairs from AICRP and ICRISAT cropping-systems trials — maize-soybean, maize-cowpea, sorghum-pigeonpea, pearl millet-groundnut, cotton-greengram, sugarcane-onion, wheat-mustard, groundnut-pigeonpea, maize-French bean and redgram-blackgram — each with sole yields and a recommended row ratio, plus a custom option for your own figures.

Yes. As long as both sole and intercrop yields for the two components share a consistent unit (t/ha or kg/ha), the indices are ratios and the unit cancels out. Do not mix tonnes for one crop and kilograms for the other, or the partial LERs and every derived index will be wrong.

Yes — if the LER falls below 1, the intercrop produced less than the sole crops would on the same land, usually because one crop suppressed the other too severely. A strongly negative aggressivity with a low LER is the warning sign. In that case widen the gap, change the ratio toward the weaker crop, or reconsider the pairing.