Abstract: Optimizing the spatial distribution of light interception is a key strategy for creating a reasonable individual and group canopy structure in cotton fields, which could increase yield and machine-picking efficiency and realize the integration of agricultural machinery and agronomy. We examined the effects of planting patterns and irrigation quotas on light interception at different canopy layers and yield formation of machine-picked sea-island cotton. A field experiment was carried out following a split-plot design in Xinjiang, Northwest China. Three planting patterns included: one film with three equal-width rows (S3), one film with four wide/narrow rows (S4), and one film with six wide/narrow rows (S6) with the same planting density. Three irrigation quotas included: 3150 m³·hm^-2 (W1, moderate deficit, 50% field capacity), 4050 m³·hm^-2 (W2, mild deficit, 75% field capacity), and 4980 m³·hm^-2 (W3, full irrigation, 100% field capacity). The results showed that increased row spacing and mild deficit watering could reduce the rate of decline of leaf area index and increase the PAR transmittance (T_r) of the lower canopy. The T_r of top, middle, and bottom layers of the canopy was distributed uniformly under S3W2 treatment, roughly in the 2∶2∶1 ratio. The distribution ratio of reproductive organs, the quality of cotton bolls, and the yield were greatly improved as a result of higher intercepted PAR rate (I_n) of the lower layer, despite a declining trend in the total I_n of the canopy. Water consumption efficiency was significantly decreased by increasing irrigation quota and row spacing. Our results suggests that the treatment of one film with three rows (S3) and mild deficit irrigation quota (4050 m³·hm^-2) did not decrease cotton yield and water use efficiency, instead of the relative balance of them, due to advantages for increasing PAR light energy transfer in the middle and lower portion of the canopy and promoting. Our results are of great significance for promoting the integration of agricultural machinery and agricultural technology of sea-island cotton and for realizing the collaborative improvement of yield and machine-picking- quality.

Key words: sea-island cotton, planting pattern, irrigation quota, photosynthetically active radiation, yield formation, water use efficiency