Effects of deficit irrigation on water-radiation use and yield of Coffea arabica under different shade cultivation modes in dry-hot region

Abstract

The yield and quality of Coffea arabica cannot be guaranteed due to irrational irrigation and light management in dry-hot region. To investigate the best coupling mode of irrigation and shade cultivation of C. arabica in dry-hot region, a field experiment was carried out with different irrigation levels and shade cultivation modes. Three levels of irrigation, i.e., full irrigation, light deficit irrigation and severe deficit irrigation, and four modes of shade cultivation, i.e., no shade cultivation (C. arabica monoculture), light shade cultivation (intercropping of four-line C. arabica and a line banana), moderate shade cultivation (intercropping of three-line C. arabica and a line banana) and severe shade cultivation (intercropping of two-line C. arabica and a line banana) were designed to examine the effects of deficit irrigation on growth, photosynthetic characteristics of lea-ves, water-radiation use and yield of C. arabica under the shade of banana trees. The results showed that net photosynthesis rate (Pn), transpiration rate (Tr), stomatal conductance (gs), leaf water use efficiency (LWUE), leaf radiation use efficiency (LRUE) increased with the increases of irrigation amount, while the intercellular CO2 concentration (Ci) decreased with the increases of irrigation amount. Compared with full irrigation, light deficit irrigation decreased dry bean yield by 9.4%, severe deficit irrigation decreased dry bean yield and water use efficiency (WUE) by 36.7% and 16.9%, respectively. Pn, Tr, gs, LWUE first increased and then decreased with the increases of shading degree, with moderate shade cultivation having the maximum increment. Compared with no shade cultivation, light shade cultivation increased dry bean yield and WUE by 13.0% and 12.9%, respectively; moderate shade cultivation increased dry bean yield and WUE by 23.1% and 23.4%, respectively. The dry bean yield, WUE, volume and fresh mass of 100-bean of C. arabica increased in different degrees with the increases of irrigation amount and shading degree, with the largest enhancement of dry bean yield and WUE occurring in full irrigation under moderate shade cultivation. Soil water content in the same soil depth decreased with the increases of shading degree. Soil water content in the same place increased first and then decreased with the increases of soil la-yer depth in 0-50 cm soil layer. Results of regression analysis showed that LRUE had a significantly negative exponential relation or Logistic-curve variation with photosynthetically active radiation. Therefore, the suitable combination of irrigation treatment and banana shade cultivation mode for C. arabica was full irrigation and moderate shade cultivation, considering the comprehensive benefit of superior quality and high production and high efficiency water-radiation use.