Relation of shape of canopy to interception of radiation and yield of wheat

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Abstract
SUMMARY: Field experiments were made at the Punjab Agricultural University, Ludhiana, during 1974–5 to 1978–9 to study the possibility of improving wheat yield by more efficient use of radiant energy through modification of the shape of the canopy under varying levels of fertilizers, irrigation and seed rates. The results showed substantial yield increase by sowing half the seed and fertilizers in one direction and half in rows at right angles, giving a spacing of 22·5 × 22·5 cm, thereby intercepting more light, which showed a significant direct relationship with yield, but there were negative correlations with soil temperature. The increase in row spacing decreased the yield. With 33% extra fertilizer than the local recommendation, sowing the crop in two directions gave 0·96 t/ha (33·4%) higher yield, whereas none of the other sowing methods showed significant increase. Mixing varieties to form a prismatic canopy gave higher yield than the mean of the varieties sown alone. Irrigating the crop more than thrice did not prove beneficial. North-south row direction tended to improve yield compared with east-west rows. Seed rates varying from 50 to 200 kg/ha showed neither significant effect, nor interaction with canopy shape except in 1978–9 when 150 kg seed/ha showed yield improvement over 100 kg/ha.