Intercropping competition between apple trees and crops in agroforestry systems on the Loess Plateau of China.

Agroforestry has been widely practiced in the Loess Plateau region of China because of its prominent effects in reducing soil and water losses, improving land-use efficiency and increasing economic returns. However, the agroforestry practices may lead to competition between crops and trees for underground soil moisture and nutrients, and the trees on the canopy layer may also lead to shortage of light for crops. In order to minimize interspecific competition and maximize the benefits of tree-based intercropping systems, we studied photosynthesis, growth and yield of soybean (Glycine max L. Merr.) and peanut (Arachis hypogaea L.) by measuring photosynthetically active radiation, net photosynthetic rate, soil moisture and soil nutrients in a plantation of apple (Malus pumila M.) at a spacing of 4 m × 5 m on the Loess Plateau of China. The results showed that for both intercropping systems in the study region, soil moisture was the primary factor affecting the crop yields followed by light. Deficiency of the soil nutrients also had a significant impact on crop yields. Compared with soybean, peanut was more suitable for intercropping with apple trees to obtain economic benefits in the region. We concluded that apple-soybean and apple-peanut intercropping systems can be practical and beneficial in the region. However, the distance between crops and tree rows should be adjusted to minimize interspecies competition. Agronomic measures such as regular canopy pruning, root barriers, additional irrigation and fertilization also should be applied in the intercropping systems.

[Main interspecific competition and land productivity of fruit-crop intercropping in Loess Region of West Shauxi].

Taking the four typical fruit-crop intercropping models, i.e., walnut-peanut, walnut-soybean, apple-peanut, and apple-soybean, in the Loess Region of western Shanxi Province as the objects, this paper analyzed the crop (peanut and soybean) photosynthetic active radiation (PAR), net photosynthetic rate (P(n)), yield, and soil moisture content. Comparing with crop monoculture, fruit-crop intercropping decreased the crop PAR and P(n). The smaller the distance from tree rows, the smaller the crop PAR and P(n). There was a significantly positive correlation between the P(n) and crop yield, suggesting that illumination was one of the key factors affecting crop yield. From the whole trend, the 0-100 cm soil moisture content had no significant differences between walnut-crop intercropping systems and corresponding monoculture cropping systems, but had significant differences between apple-crop intercropping systems and corresponding monoculture cropping systems, indicating that the competition for soil moisture was more intense in apple-crop intercropping systems than in walnut-crop intercropping systems. Comparing with monoculture, fruit-crop intercropping increased the land use efficiency and economic benefit averagely by 70% and 14%, respectively, and walnut-crop intercropping was much better than apple-crop intercropping. To increase the crop yield in fruit-crop intercropping systems, the following strategies should be taken: strengthening the management of irrigation and fertilization, increasing the distances or setting root barriers between crop and tree rows, regularly and properly pruning, and planting shade-tolerant crops in intercropping.

[A study of mechanical ventilation pattern in different recovery stages of muscle relaxant after general anesthesia].

OBJECTIVE: To observe the effects of intermittent positive pressure ventilation (IPPV), synchronized intermittent mandatory ventilation (SIMV), and biphasic intermittent positive airway pressure (BiPAP) on the recovery time of automatic breathing in patients in different stages of recovery of general anesthesia with muscle relaxant. METHODS: Thirty patients were randomly divided into three groups. The initial ventilation pattern was IPPV for all patients. After the last dose of muscle relaxant, the pattern of ventilation of group II and group III was adjusted to SIMV and BiPAP, respectively. The airway peak pressure(Ppeak), minute ventilation(MV), expiration carbon dioxide(P(Et)CO(2)), blood gases, and the interval between the last dose of muscle relaxant and automatic breathing(LR-S) was observed. RESULTS: (1) When T(1) appeared, Ppeak of the BiPAP group was lower than that of the IPPV group and SIMV (all P<0.01). When T(R)=0.75, Ppeak of IPPV group was lower compared with the SIMV and BiPAP groups (all P<0.01). (2) When T(1) re-appeared, the MV of BiPAP was higher than that of the IPPV group (P<0.05), but was not different from that of the SIMV group (P>0.05). When T(4) appeared, T(R)=0.25, T(R)=0.75, MV of SIMV group and BiPAP group was higher than that of IPPV group (all P<0.01). (3) When T(R)=0.25, T(R)=0.75, the P(Et)CO(2) of the SIMV group and BiPAP group was lower than that of IPPV group (all P<0.05). (4) Partial pressure of carbon dioxide in artery (PaCO(2)) of the SIMV and BiPAP group was lower than that of the IPPV group (all P<0.05). (5) The LR-S before extubation was shorter in SIMV and BiPAP group than that in IPPV group (P<0.05). CONCLUSION: SIMV and BiPAP have the advantages as follows: no confrontation between mechanical ventilation and autonomous breathing, quick recovery of autonomous breathing, little change in airway pressure, high MV and low P(Et)CO(2). So SIMV and BiPAP are more suitable for recovery from anesthesia. In addition, BiPAP can lower the airway's peak pressure and decrease the probability of barotrauma therefore it is more suitable for those patients with high airway pressure.