Manipulation of dry matter accumulation and partitioning with plant density in relation to yield stability of cotton under intensive management

Cotton (Gossypium hirsutum L.) yield under extensive field management across a certain range of plant population densities can be stabilized by manipulating the number of bolls and boll weight, but little is known of similar yield stability under intensive management and how the yield stability is achieved by dry matter accumulation and partitioning under various plant densities. A field experiment was conducted to study the effects of plant density (1.5, 3.3, 5.1, 6.9, 8.7 and 10.5plantsm−2) on dry matter accumulation and partitioning in relation to cotton yield. The seedcotton and lint yields at 1.5plantsm−2 were significantly lower than those at other plant densities, but there was little difference in either seedcotton or lint yield among plant densities ranging from 3.3 to 10.5plantsm−2. Plant biomass increased gradually with increasing plant density. The ratio of dry weight of fruiting forms to plant biomass (DWFF/PB) at 135 days after sowing (DAS) at 1.5plantsm−2 exceeded those under 5.1plantsm−2 by 12.3%, 6.9plantsm−2 by 12.7%, 8.7plantsm−2 by 20.5% and 10.5 plants m−2 by 21.8%. Also, the harvest index at 1.5plantsm−2 exceeded those at 5.1, 6.9, 8.7 and 10.5plantsm−2 densities by 16.2, 16.2, 34.3, 38.7%, respectively. Seedcotton yield was positively correlated with total biomass at extremely low plant density (1.5plantsm−2), but was better correlated with DWFF/PB at higher densities (5.1–10.5plantsm−2). The boll weight of the last harvest was 6.0–6.3% lower than those of the first two harvests at 1.5plantsm−2. Leaf senescence as indicated by reduced Pn and leaf area index (LAI) in later season occurred earlier at 1.5plantsm−2 than other plant densities. It was concluded that cotton yield is relatively stable across a wide range of plant densities even under intensive field management. The stability was achieved mainly through manipulation of dry matter accumulation and partitioning. The reduced boll weight of the last harvest was mainly due to earlier leaf senescence at 1.5plantsm−2, which might explain the lower cotton productivity per unit ground area at such a low plant density.