| Water shortage, soil secondary salinization and inefficient use of fertilizer are the main factors that limiting the sustainable development of agriculture in Hetao Irrigation District (HID), which is located in the west part of Inner Mongolia. Investigating the mechanisms of saving water and fertilizer and building reasonable water and fertilizer managing patterns is a promising way to solve these problems. Previous studies has demonstrated radiation interception and use efficiencies are the determinant factors for crop production when the water and fertilizer are not limited. Constructing proper canopy structure and enhancing leaf photosynthesis rate is one of the key point for improving crop radiation use efficiency. Therefore, investigating the effects of water and fertilizer regulation on canopy structure and photosynthesis efficiency is significant for building reasonable water and fertilizer managing patterns and sustainable development of agriculture in HID.In this study, a field study was conducted at Shahaoqu Experimental station (located in the center part of HID and the soil is moderate salinized) to investigate the effects of water and fertilizer regulation on canopy structure and photosynthesis efficiency of sunflower, one of the main cash crop in the study area. Membership function method was used to evaluate the effects of water and fertilizer regulation. Main conclusions are as follows:1. The yield, water use efficiency and IWUE of sunflower was the greatest under the treatment with 108 mm water and 68.8 kg hm-2 nitrogen applied before seeding and 72 mm water and 68.8 kg hm-2 applied during squaring stage, which was 20.5%,23.1% and 50.6% than the control treatment (CK). Hundred grain weight, grain number per plant and maturing rate are significantly improved optimal treatment (P<0.05).2. Photosynthesis rate of sunflower initial growing stage was increased as the decrease of fertilizer application and decreased as the decrease of water application before seeding. Moderate decrease of water application (108 mm) did not decrease the photosynthesis rate significantly. Reducing the fertilizer and water application would improve the photosynthesis rate during maturing stage significantly compared with the CK. The photosynthesis rate under 20% reduction of water and 20% reduction of fertilizer was the greatest.3. The biomass accumulation of sunflower from seedling to squaring increased as the increase of water application before seeding, however, the increase under 20% water reduction was not significantly different from CK. The growth of sunflower under water reduction before seeding was compensated during flowering stage after water application during squaring.20% reduction of water and 20% reduction of fertilizer during squaring obtained the highest growth rate and its biomass accumulation after harvest because its leaf area index (LAI) decreased 20.3% slowly compared with the CK and thus its photosynthesis rate during late growth stage was relatively higher.4. Light interception by the sunflower canopy decreased and the increase of fertilizer application when water application was the same. Reasonable reduction of water and fertilizer application (B1ã€B2ã€B3) could improve the photosynthesis rate significantly (P <0.05). The treatment with 20% reduction of water and 20% reduction of fertilizer obtained the greatest radiation interception efficiency since its LAI kept a relatively high level during the late growth stage and the canopy structure was more suitable for light interception.5. Those managing patterns with reduced water or/and fertilizer application obtained significantly greater radiation use efficiency (RUE) compared with the CK (P<0.05). RUE of the treatment with 20% reduction of water and 20% reduction of fertilizer was significantly greater since soil water under this treatment was not significantly lower while soil salinity under this treatment was significantly lower compared to other treatment (P< 0.05). |
