畦灌配施保水剂改善杨树林下土壤物理性状提高微生物活性

为指导杨树人工林节水灌溉和增产,通过大田试验,比较研究常规畦灌(720 m3/hm2)、常规畦灌量60%、常规畦灌量30%、60%常规畦灌量配施保水剂和30%常规畦灌量配施保水剂等处理对杨树林下土壤容重、微生物量碳和氮、微生物活性及生长的影响。结果表明:同常规畦灌相比,60%常规畦灌量配施保水剂处理明显降低了土壤容重,且显著增加了土壤总孔隙度和毛管孔隙度,其土壤容重分别较常规畦灌、常规畦灌量60%、常规畦灌量30%和30%常规畦灌量配施保水剂处理下降6.62%、11.19%、16.45%和7.97%;显著提高了土壤微生物量碳、氮含量,并明显增强了土壤微生物呼吸作用,其微生物呼吸速率较常规畦灌、常规畦灌量60%、常规畦灌量30%和30%常规畦灌量配施保水剂处理分别高出13.89%、24.24%、41.38%和12.33%;同时,60%常规畦灌量配施保水剂处理还降低了代谢熵,与其他4种处理相比其下降幅度分别为5.96%、8.84%、11.72%和4.78%。此外,该处理的材积生长率达到最大值,并显著大于其他处理(P0.05)。与60%常规畦灌量配施保水剂相比,30%常规畦灌量配施保水剂处理对林下土壤及材积的作用效果较小。相关分析表明,材积生长率与毛管孔隙度、代谢熵有极显著相关关系(P0.01),与土壤容重、微生物量碳和氮、微生物呼吸有显著相关关系(P0.05)。综合分析认为,适宜的节水灌溉措施(常规畦灌量60%与保水剂组合)有利于改善杨树林下土壤的物理环境,增强微生物活性,并促进杨树林木的生长。

Border irrigation co-applied with super absorbent polymers improving soil physical characteristics and increasing microbial activity in poplar forest

Abstract: Super absorbent polymers can absorb water up to a few hundred or even a few thousand times their own mass. The special physical structure, unique chemical composition and characteristics of high water absorption capacity allow super absorbent polymers to be widely used in water-saving agriculture, horticulture and other industries to relieve drought and reserve water for farmland, seedling protection and crop yield improvement. A large number of studies have showed that super absorbent polymer has the properties of water saving and drought resistance. But the application amount of super absorbent polymer is an important parameter to evaluate. Applying with the improper amount can result in bad effects, either no effect, or soil permeability compromised if excess super absorbent polymer is used. This can cause plant roots to have difficulty in breathing or to get rotten. In the meantime, border irrigation is also an efficient measure which has the advantages of low cost, simple operation and easy popularization. Similarly, the irrigation quantity is a vital factor. Because excess irrigation not only causes the waste of water resource, but also poses a threat to the groundwater. While insufficient irrigation may have no effect. Therefore, it is speculated that super absorbent polymer co-applied with border irrigation should be an interesting thing, and investigating their appropriate proportion has important theoretic value and practical significance. However, there is little information on the effect of border irrigation measure co-applied with super absorbent polymer on the forest-tree plantation. With the purpose of promoting water-saving irrigation and poplar yield, a field experiment of 5 treatments, i.e. CK (conventional border irrigation), I60 (60% conventional border irrigation quantity), I30 (30% conventional border irrigation quantity), I60S (60% border irrigation quantity co-applied with super absorbent polymers) and I30S (30% border irrigation quantity co-applied with super absorbent polymers) was designed and performed. The present study was conducted to determine the effects of different treatments on bulk density, microbial biomass carbon (MBC), microbial biomass nitrogen (MBN) and microbial activity in the forest soil as well as the growth of poplar. Results showed that in comparison to CK treatment, I60S treatment significantly reduced soil bulk density and obviously increased soil total porosity and capillary porosity, indicative of 6.62%, 11.19%, 16.45% and 7.97% decreases in soil bulk density compared to the treatments of CK, I60, I30 and I30S, respectively. The I60S treatment also evidently increased MBC and MBN contents and significantly enhanced microbial respiration, showing 13.89%, 24.24%, 41.38% and 12.33% increases in microbial respiration rate over the treatments of CK, I60, I30 and I30S, respectively. At the same time, the metabolic quotient was reduced by the I60S treatment, demonstrating 5.96%, 8.84%, 11.72% and 4.78% decreases, respectively. Additionally, the volume growth rate of the I60S treatment also reached the maximum, which had significant differences with other treatments (P<0.05). However, in the I30S treatment, less effect on the forest soil characteristics and the volume growth were observed than that in the I60S treatment. The correlation analysis showed that the volume growth rate was extremely significantly correlated with capillary porosity and metabolic quotient, and had significant correlation with soil bulk density, MBC and MBN contents and microbial respiration. In conclusion, the proper water-saving irrigation measure (60% border irrigation quantity co-applied with super absorbent polymers) is beneficial to improving soil physical environment and enhancing microbial activity in forest soil, as well as the growth of poplar.