RESUMO
Taking the main production area of yam in North China Plain as the research area, we analyzed the status of soil fertility and fertilizer application in yam production through field investigation and tracking monitoring, examined soil nutrient balance using the input-output model of nutrients in agricultural system, and assessed the environmental risks in the yam planting system. The results showed that: 1) the contents of soil organic matter and total N were extremely low, and the contents of available P and available Zn were both low; both nitrate and available Cu contents were at the middle level, the contents of soil slowly available K, available S, and exchangeable Ca and Mg were all extremely high, the contents of available K, available Fe, and available Mn were all at high level; 2) The nitrogen (N), phosphorus (P2O5), and potassium (K2O) inputs were 575-943 kg·hm-2, 341-981 kg·hm-2, and 655-1219 kg·hm-2 during the whole growth period of yam, with chemical fertilizer accounting for 83.0%, 88.6%, and 91.3%, respectively; The input imbalance between organic and inorganic fertilizer, as well as the excessive nutrients input were prominent; 3) The surplus rate of soil nitrogen, phosphorus and potassium reached 271.14 kg·hm-2, 466.34 kg·hm-2, and 739.97 kg·hm-2, with corresponding surplus ratio of 48.7%, 258.1%, and 324.5%, respectively, which all exceeded the environmental safety threshold and were classified as moderate risk, severe risk, and severe risk, respectively. The overall environmental risk caused by chemical fertilizer application in yam production had reached severe risk level.
Assuntos
Dioscorea , Solo , China , Nutrientes , Medição de RiscoRESUMO
In October 2015, soil samples with different salinity were collected in a coast area in Yuyao, Zhejiang, and soil microbial community composition, soil catalase, urease activities, as well as soil physical and chemical properties were studied. The results showed that Nitrospira took absolute advantage in the bacterial community, and showed good correlations to total potassium. Cladosporium and Fusarium were predominant in the fungal community. Meanwhile, Cladosporium was related to soil urease and total nitrogen, and same correlation was found between Fusarium and soil urease. Catalase activity ranged from 3.52 to 4.56 mL·g-1, 3.08 to 4.61 mL·g-1 and 5.81 to 6.91 mL·g-1 for soils with heavy, medium and weak salinity, respectively. Catalase activity increased with the soil layer deepening, which was directly related to soil total potassium, and indirectly related to pH, organic matter, total nitrogen and total phosphorus through total potassium. Soil urease activity ranged among 0.04 to 0.52 mg·g-1, 0.08 to 1.07 mg·g-1 and 0.27 to 8.21 mg·g-1 for each saline soil, respectively. Urease activity decreased with soil layer deepening which was directly related to soil total nitrogen, and was indirectly related to pH, organic matter and total potassium through total nitrogen. The total phosphorus was the largest effect factor on the bacterial community CCA ordination, and the urease was on fungal community.
Assuntos
Salinidade , Microbiologia do Solo , Solo/química , Bactérias , Catalase/análise , China , Fungos , Nitrogênio/análise , Fósforo/análise , Potássio/análise , Urease/análiseRESUMO
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.