| Relay intercropping is a commonly used agronomic practice in China for many years. Suitable crop relay intercropping pattern can use nutrient, water and solar radiation resources efficiently and enhance crop yield enormously. Capsicum (Capsicum.annuum L.) is a unique export-oriented agriculture product in China, which is mostly planted by relay intercropping pattern and has achieved significant relay intercropping yield advantage. Therefore, capsicum relay intercropping pattern is attracting more and more agronomists′and ecologists′attention. In this paper, physiology and ecology mechanisms of capsicum/maize (Zea mays L.) relay intercropping system were studied by the way of pot culture experiments, field growth experiments and different interspecific root barriers technique. The objective of the work is to give scientific evidence for improving productivity and higher efficient resource utilization in relay intercropping system. The following main results were obtained in the experiments.Capsicum/maize relay intercropping not only altered solar radiation distribution in crop population, but also enhanced chlorophyll a and chlorophyll b content of capsicum and maize function leaves markedly. Compared to monoculture maize and capsicum, Capsicum/maize relay intercropping depressed the descending rate of function leaves chlorophyll content in the process of leaves senescence. Capsicum/maize relay intercropping improved the maximum net phointercropping reduced the maximum net photosynthesis rate of sloe growth capsicum leaf, especially in cloudy, reduced by 55.65%. In this relay intercropping system, diurnal average photo use efficiency of capsicum was enhanced. There was a different linear relationship between photosynthetic active radiation and photosynthesis in the different capsicum growth stage.The average height of relay-intercropped maize and capsicum plant respectively exceeded that of monoculture maize and monoculture capsicum. Compared to monoculture maize, the volume, surface area, average diameter, tip number and chiasma number of relay-intercropped maize were improved. Root top ratio of relay-intercropped maize was increased by 37.77% as compare with monoculture. Morphological configuration characteristic of relay-intercropped capsicum took on weak current and root top ratio increasing as compare with monoculture capsicum. The root activity of relay intercropping components was enhanced in capsicum/maize relay intercropping system, and the increase extent of capsicum root activity exceeded that of maize root activity.In the whole grow stage, average LAI (leaf area index) of capsicum/maize relay intercropping system increased by 22.47% as compared with monoculture capsicum; reduced by 2.46% as compared with monoculture maize. The number of day, which LAI of capsicum/maize relay intercropping system exceeded 3, increased by 1.33 times as compared with monoculture capsicum; increased by 19.32% as compared with monoculture maize. There was a marked relay intercropping yield advantage in the capsicum/maize relay intercropping system, LER (Land equivalent ratio) of biological yield was equal to 1.29, and LER of economy production yield was equal to 1.33, economy production yield advantage more significant than biological yield advantage. Economy production yield and biomass yield advantage of capsicum/maize relay intercropping system not only resulted from crop interspecific interaction of above-ground but also below-ground interspecific root interaction, and furthermore, relative contribution of above-ground accounted for 75% and relative contribution of below-ground accounted for 25%.Grain (fruit) number to leaves number ratio and grain (fruit) weight to leaves number ratio of capsicum and maize crop in relay intercropping system exceeded those of monoculture capsicum and maize completely. Compared to monoculture capsicum and maize, there was a bigger PRA interception efficient in capsicum/maize relay intercropping system. PRA interception efficient of capsicum/maize relay intercropping system raised by 46.5% as compared with the weight average of PRA interception efficient of monoculture crop according to relay intercropping growth proportion. Photo-energy utilization efficiency of capsicum/maize relay intercropping system reduced by 11.7% as compared with the weight average of Photo-energy utilization efficiency of monoculture crop according to relay intercropping growth proportion. The yield advantage of capsicum/maize relay intercropping system resulted from the increase of PRA interception efficient, not from the increase of Photo-energy utilization efficiency. Shoot dry matter accumulation rate of relay-intercropped capsicum had bigger absolute value of rate, and smaller relation rate as compared with that of monoculture capsicum. The shoot dry matter accumulation rate of relay-intercropped maize exceeded far it or monoculture maize.The proportion, which relay-intercropped capsicum plant dry matter was allocated to stem and branch, was smaller, and which relay-intercropped capsicum plant dry matter was allocated to fruit and root, was bigger, as compared with those of monoculture capsicum. The proportion of relay-intercropped capsicum plant dry matter was allocated to root increase by 2.6% as compared with it of monoculture capsicum. Dry matter allocation proportion of different organ of maize plant had no distinct difference between relay-intercropped maize and monoculture. Compared to that of monoculture maize, the dry matter allocation proportion of stem of intercropped maize was reduced; however it increased in root of intercropped maize.In the whole grow stage, nitrogen (N), phosphorus (P) absorption quantity of relay-intercropped maize were always more than those of monoculture maize. During the symbiosis of maize and capsicum, N, P absorption of capsicum were inhibited, however, N, P absorption quantity of relay-intercropped capsicum plant showed marked recovery phenomena after maize harvest, finally N, P absorption quantity of relay-intercropped capsicum were attained or exceeded N, P absorption quantity of monoculture capsicum. N, P nutrition competition ratio of relay-intercropped maize relative to relay-intercropped capsicum decreased after application of N fertilizer. Relay intercropping growth pattern almost did not influence potassium (K) absorption of relay-intercropped capsicum and maize, compared to monoculture capsicum and maize. N, P nutrition absorption of capsicum showed side row disadvantage in capsicum/maize relay intercropping system. However, these phenomena did not happen in the K nutrition absorption of relay-intercropped capsicum. The result of pot culture and field culture experiments showed, relay intercropping growth pattern improved N, P, K nutrition absorption quantity of relay intercropping crop as compared with monoculture, the increase extent of relay intercropping crop nutrition relative to monoculture decreased after application of N fertilizer. Use efficient of N, P and K nutrition in the capsicum/maize relay intercropping system was less than monoculture.Bacteria, fungi and actinomycete number of rhizosphere and non- rhizosphere soil in the capsicum/maize relay intercropping system were generally more than monoculture capsicum and maize in the whole grow stage, there was a relay intercropping rhizosphere effect in the capsicum/maize relay intercropping system. Microbial biomass carbon and nitrogen content of rhizosphere soil of relay-intercropped crop was more than monoculture crop. Average well color development (AWCD) value, simpson diversity index, shannon diversity index, probability of interspecific encounter (Pie) and alatalo evenness of relay-intercropped crop were all more than these diversity indexes of monoculture. There was a positive correlation or significantly positive correlation between crop biological yield and these diversity indexes, this suggested that soil microbial diversity might play an important role in the process of crop growth.Microbial number, enzyme activity and effective nutrition content of rhizosphere and non-rhizosphere of relay-intercropped maize and capsicum were all more than monoculture, this indicated soil micro ecology mechanism of relay intercropping advantage. Rhizosphere soil effective nutrition content of crop was less than non-rhizosphere soil effective nutrition content of crop. Soil important microbe group number was main factor influencing soil enzyme activity; as well, there was a significant correlation between them (p<0.01). The content of organic matter and alkali-hydrolyzable nitrogen were also significantly correlated with soil microbe number and enzyme activity (p<0.01), available phosphor content was positively correlated with soil microbe number and enzyme activity. Soil fungi number and urease activity were negatively correlated with soil available potassium content. After the pathway analysis was done between soil nutrients content and biological factors, a conclusion was drawn, the urease, catalase, bacteria, protease were the main biological factors of deposit of organic matter; the surcease was the most important factor affecting alkali-hydrolyzable N; the urease was the most important factor affecting available P; the bacteria was the most important factor affecting available K; the alkaline phosphatase and fungi only selectively affected the deposit of organic matter and the forming of available nutrients of N, P and K. The direct path coefficients were negative between actinomycete and soil nutrient, which showed that actinomycete affected soil nutrient slightly.
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