| Forest-grass intercropping can not only coordinate the contradiction between the land use of forest and livestock husbandry,but also improve the utilization efficiency of above-and belowground resources,ameliorate soil structure and fertility and increase biodiversity.According to herbage demand and planning of Ningxia,introduced herbage into ’LingwuChangzao’ jujube cultivation to form a new pasture production mode.9 kinds of planting patterns were studied.By carrying out this research,we clarified the productivity performance of intercropping systems under different planting patterns,explored the physiological and ecological driving mechanisms of system productivity improvement from three perspectives including light utilization characteristics,the nutrient(N,P and K)uptake and utilization efficiency and soil environment,and determined the key factors affecting the yield and quality of jujube and herbage.Meanwhile,the ecological mechanism of intercropping yield and nutrient uptake dominance was explained through the net effects of diversity:complementarity(CE)and selection effects(SE).We comprehensively evaluated the effects of different planting patterns on the production,screened out suitable’LingwuChangzao’ jujube-herbage intercropping patterns for promoting cultivation in arid sandy areas of Ningxia.The main results are as follows:(1)’LingwuChangzao’jujube-herbage intercropping could promote herbage growth,increase the yield of jujube-herbage,and change the quality of jujube-herbage.Intercropping significantly increased height,the tiller and branches number,leaf area,stem-leaf ratio and freshdry ratio of herbage.In addition,the maximum dry matter accumulation and maximum daily growth rates of 4 herbages in intercropping were higher than those in monoculture.In the’LingwuChangzao’ jujube-herbage intercropping systems,the yield of ’LingwuChangzao’ jujube was significantly increase by 21.18%-104.45%compared with that of monoculture,the total yield of perennial ryegrass,annual fescue,wheatgrass and alfalfa were significantly increase by 8.90%,8.03%,20.97%and 14.57%,respectively compared with that of monoculture.The land equivalent ratio of 4 intercropping patterns ranged from 1.02 to 1.96,and showed a significant yield advantage of intercropping over monocropping.Compared to monoculture,intercropping was beneficial for improving the fruit quality of jujube,but had no significant impact on the herbage quality.(2)Intercropping could increase the net photosynthesis rate of herbage,and alleviated the phenomenon of photosynthetic acclimation.The leaf area index,net photosynthetic rate,stomatal conductance,transpiration rate and light utilization rate of perennial ryegrass,annual fescue and alfalfa in intercropping were significantly higher than those in monoculture,the increases were 20.36%-105.1 4%,26.55%-48.77%,35.63%-209.84%,19.66%-208.37%,9.1 4%-12.42%,respectively.Intercropping regulated the photochemical electron transfer efficiency and activity of the photoreaction center of herbage,promoting the energy capture and adaptability to the high-light environment.The increasement of leaf maximum net photosynthetic rate,light saturation point,carboxylation efficiency,maximum carboxylation rate,maximum electron transport rate and triose phosphate utilization promoted the increase of net photosynthetic rate,enhanced the carbon fixation and carboxylation ability of the leaf,and thus promoted growth and adaptability of herbage.(3)Compared with jujube monoculture,intercropping significantly increased the nutrient(N,P and K)uptake of ’LingwuChangzao’ jujube by 28.14%-130.34%,42.15%-127.09%and 22.46%-124.88%.Intercropping significantly increased the nutrient(N,P and K)uptake of perennial ryegrass,annual fescue,wheatgrass and alfalfa by 16.54%-79.34%,14.60%-96.77%,13.65%-87.43%compared with herbage monoculture.Among the intercropping patterns,’LingwuChangzao’ jujube-alfalfa had the highest N and K uptake while the highest P uptake was found from ’LingwuChangzao’ jujube-perennial ryegrass.(4)Yield changes and nutrient uptake availability advantages of ’LingwuChangzao’ jujubeherbage intercropping systems were driven by the complementarity effects(CE)and selection effects(SE).The yield and N,P and K uptake advantages in ’LingwuChangzao’ jujube-perennial ryegrass intercropping pattern were the result of positive CE and SE.Enhanced yield and N,P and K uptake derived from positive CE and negative SE in ’LingwuChangzao’ jujube-annual fescue and ’LingwuChangzao’ jujube-alfalfa intercropping patterns.The yield and N,P and K uptake advantage are not obvious by ’LingwuChangzao’ jujube-wheatgrass resulted from the negative SE offset some positive CE.CE played a major role in the contribution of yield and N,P and K uptake.Therefore,it is necessary to increase the CE in the intercropping system to ensure a significant yield advantage.(5)Intercropping changed the physicochemical properties of soil.The content of>0.25 mm aggregate in soil increased compared with that of the corresponding monoculture.The contents of soil water,total nitrogen,total potassium,available phosphorus,available potassium,nitrate nitrogen and ammonium nitrogen were significantly increased under the intercropping patterns,while the bulk density,pH and total phosphorus were significantly decreased.4 intercropping patterns significantly increased the content of the soil organic carbon fractions compared to monoculture,which promoted the formation and accumulation of soil organic carbon storage,with an increase of 9.69%-64.97%.Specifically,’LingwuChangzao’ jujube-annual fescue intercropping pattern had higher carbon cycling enzymes:β-1,4-glucosidase and cellobiohydrolase,and’LingwuChangzao’jujube-perennial ryegrass intercropping increased the activity of nitrogen cycling enzymes:β-1,4-N-acetylglucosaminidase and urease.These 2 intercropping patterns were more conducive to improving the carbon and nitrogen level of soil.Besides,intercropping significantly increased the diversity of soil bacteria and fungi,and had a higher impact on bacteria than fungi.The abundance of Proteobacteria,Actinobacteria,Bacteroidota and Ascomycota apart in bacteria and fungi increased significantly under the intercropping patterns.The results of redundancy analysis and mental test showed that the BD,BG,SWC,AP and AKP were the key soil factors affecting the composition and diversity of microbial community.Structural equation modeling showed that the interaction of the nutrient uptake of plants,soil physicochemical properties and soil enzyme activities together explained the variation of 81%in yield.The nutrient uptake of plants had the greatest impact on yield,followed by soil physicochemical properties and soil enzyme activities.(6)Herbage light characteristics,the nutrient uptake,soil characteristics and microbial diversity affected yield and quality through direct/indirect effects.SEM showed that the direct/indirect effects of herbage light characteristics,the nutrient uptake,soil characteristics and microbial diversity explained 84%of the variance in yield and 90%of the variance in jujube fruit quality and 88%of the variance in herbage quality,respectively.In terms of yield effect,the herbage light characteristics(-0.231),soil characteristics(-0.463),nutrient uptake(-0.204),microbial diversity(-0.400)all showed negative effects;In terms of jujube fruit quality effect,the herbage light characteristics(-0.197)showed a negative effect,soil characteristics(0.816),nutrient uptake(0.015),microbial diversity(0.333)all showed positive effects;In terms of herbage quality,the herbage light characteristics(-0.847),nutrient uptake(-0.590),microbial diversity(-0.046)all showed negative effects,soil characteristics(0.802)showed a positive effect.LingwuChangzao’jujube-perennial ryegrass and ’LingwuChangzao’ jujube-annual fescue intercropping patterns were finally selected by using the entropy weight DTOPSIS method.In summary,based on the 6 m row spacing of ’LingwuChangzao’ jujube,’LingwuChangzao’jujube-herbage intercropping can significantly improve system productivity.This is because the interaction in the intercropping regulated the light utilization characteristics,promoted nutrient uptake and utilization efficiency of plants and improved soil environment.Intercropping advantages derived from interaction between CE and SE among species,and interspecific facilitation may play a key role in enhancing intercropping productivity.Consequently,’LingwuChangzao’ jujube-perennial ryegrass and ’LingwuChangzao’ jujube-annual fescue intercropping were the recommended ’LingwuChangzao’ jujube planting patterns in Ningxia. |
PDF Full Text Request