RESUMO
From May to October in 2017, the sap flow, water consumption and the effects of environmental factors on the sap flow of Amorpha fruticosas with different stem diameters under different water and salt conditions were examined with the packaged sap flow measuring system in a secondary saline-alkali land of Ningxia Yellow River irrigation area. The sap flow rate showed a broad peak curve with no obvious phenomenon of 'midday break' in sunny days and a multi-peak curve in cloudy, overcast and rainy days. Weak sap flow was found at night. In the growing season (May - October), total sap flow of A. fruticosas with basal stem diameters of 13, 16 and 22 mm were 138.14, 206.06, 370.11 kg, respectively. The water consumption was largest in June and July, accounting for about 50% of the whole growing season, followed by May and August, and lowest in September and October. At both 0.5 h and day scales, photosynthetically active radiation (PAR) was the dominant meteorological factor affecting the sap flow. In the first growth stage (May 13th - August 19th), soil water in shallow layer (0-40 cm) had significant effect on the sap flow of A. fruticosas with three different diameters, and soil salt in shallow layer had significant inhibitory effect only on A. fruticosa with the diameter of 13 mm. In the second growth stage (August 20th - October 10th), soil water and soil salt had no significant effect on A. fruticosas with three different diameters. In summary, the A. fruticosas with diameters <13 mm was not suitable for planting in saline soil (electrical conductivity (EC)>2 dS·m-1), and individuals with diameters >16 mm could grow well in saline soil (EC=5 dS·m-1). Moreover, reasonable irrigation should be carried out in the vigorous growth stage of the A. fruticosas.
Assuntos
Irrigação Agrícola , Fabaceae/fisiologia , Caules de Planta/fisiologia , Álcalis , China , Rios , Solo , ÁguaRESUMO
Taking a typical apple×maize intercropping system in the loess region of Shanxi Pro-vince, China as test object, the current study analyzed the photosynthetic characteristics of maize leaves of ear position at filling stage under different irrigation and fertilization regimes. There were three irrigation levels [low (W1), 50% field capacity (Fc); medium (W2), 65% Fc; and high (W3), 85% Fc], three fertilizer levels {F1 [N (289 kg·hm-2) + P2O5 (118 kg·hm-2) + K2O (118 kg·hm-2)]; F2 [N (412.4 kg·hm-2) + P2O5 (168.8 kg·hm-2) + K2O (168.8 kg·hm-2)], F3 [N (537 kg·hm-2) + P2O5 (219 kg·hm-2) + K2O (219 kg·hm-2)]}, and a control (CK, no irrigation and fertilization throughout the growing season). The nine irrigation and fertilization treatment combinations were W1F1, W2F1, W3F1, W1F2, W2F2, W3F2, W1F3, W2F3, and W3F3, respectively. The results indicated that different water and fertilizer regimes had no significant effect on the variation in diurnal photosynthetic indexes. However, the application of water and fertilizers considerably increased the peak value of net photosynthetic rate (Pn), exten-ded the stomatal opening period, influenced the lowest value of intercellular CO2 concentration (Ci), and reduced the maximum value of water use efficiency (WUE) during the day. The limiting factors affecting photosynthesis were nonstomatal factors. Stomatal conductance (gs) and transpiration rate (Tr) were both significantly negatively correlated with the distance from tree line (P<0.01). WUE were significantly positively correlated with the distance from the tree line (P<0.05). gs decreased by 0.028-0.093 mol·m-2·s-1, Tr decreased by 0.56-1.41 mmol·m-2·s-1, WUE increased by 0.08-1.00 µmol·mmol-1, as the average distance from the tree line increased by 1 m. Thus, irrigation and fertilizers significantly increased the mean value of Pn, Tr, and gs, but decreased the mean value of WUE during the day. The W3F1 treatment had the highest mean values of Pn(10.64 µmol·m-2·s-1), gs(0.295 mol·m-2·s-1), WUE (3.05 µmol·mmol-1), but a lower mean value of Tr(4.32 mmol·m-2·s-1) compared with the other treatment combinations during the day. When the total irrigation rate was 1300 m3·hm-2, the total fertilization rate was 525 kg·hm-2, Pn was at its maximum, and the theoretical maximum value was 10.32 µmol·m-2·s-1. Therefore, the W3F1 treatment was the irrigation and fertilizer regime that was most likely to improve the photosynthetic efficiency of the apple-maize intercropping system.
