Study On The Effect Of Field Configuration On Light Environment, Light Utilization And Yield In Maize-soybean Relay Strip Intercropping

The maize and soybean relay strip intercropping pattern is one of the most important way to ensure national food security and revitalize China’s soybean industry. So it will be of great significance to find a way increasing the total yield, by which the light distribution, the light interception and radiation use efficiency can be improved and the response mechanism of the morphology and yield of soybean to the light environment can be ascertained. Therefore, we carried out a series of field experiments in two counties of Sichuan province from 2013(Ya’an) to 2014(Renshou) and the Chuandan 418 and Nandou 12 were used as the experiment materials. The designs of different maize-soybean relay strip intercropping systems were based on the narrow row distance of maize (or the distance between the maize and soybean rows), and the sole maize and sole soybean were used as the controls. The light distribution and RUEs of the systems, the morphologies response of both crops, the recovery growth of soybean and the change of total yield were investigated. The main conclusions were as follows:1. The PAR transmittance and R/Fr values of soybean canopy were decreasing with the narrow row distance increasing. The maximum and minimum of PAR transmittance of wide row of maize were 35.3%,14.1% and 25.9%,5.8% in "20+180" and "100+100" treatment separately when the soybean was sowed which were 215.8%,25.9% and 334.8% higher,3.0% lower than sole maize in 2013 and 2014. The maximum of PAR transmittance in the wide row of soybean canopy were 48.8% and 19.7% in "20+180" treatment during the seedling stage in 2013 and 2014 which were 372.7% and 168.8% higher than the sole maize separately, but there was little difference between the minimum and the value of sole maize. The maximum and minimum values of R/Fr at the soybean canopy were 0.68 and 0.32 in "20+180" and "100+100" treatment seperately when soybean was at the stage of emergence in 2014, which were lower than sole soybean by 49.3% and 76.0% separately. And the same indexs were 0.63 and 0.47 at the seedling stage of soybean, which were 47.9% and 61.5% lower than sole soybean separately.2. The light interception and RUE of maize were increasing with the narrow row distance increasing. The maximum of RUE in the relay intercropping was 2.700 g/MJ in the "20+180" between the silking stage and filling stage, which had little difference with the sole maize and the other treatments are lower than the "20+180" treatment by 17.9%,18.4%,11.5%, and 6.9%. Instead, the light interception and RUE of soybean were decreasing with the narrow row distance increasing. The maximum of light interception appeared in the R4 stage.The values of RUE of all treatments arrived at the maximum from R2 to R4 stage and the maximum was 2.788g/MJ in sole soybean and the other treatments were 29.359.3%、64.7%、85.4% and 86.1% lower than the sole soybean. The RUEs of maize in the whole growth period were increasing with the narrow row distance increasing but RUEs of soybean were in the opposite trend in maize and soybean relay strip intercropping system. The RUEs of maize and soybean relay strip intercropping system were higher than monoculture system and the maximam of RUE was 1.65% in "20+180".3. The light environment had an immediate impact on the morphology and yield of both crops at the co-existence period. The correlation analysis showed that the plant height, stem diameter, LAI, shoot biomass and yield of maize are extremely significantly or significantly negatively correlated with the total PAR transmittance at the bottom of maize; there were negative correlations between the plant height and length of first internode of soybean with the PAR transmittance of soybean canopy, but the stem diameter, LAI, shoot biomass and yield of soybean showed significantly positive correlations with the PAR transmittance and R/FR value.4. The morphology, LAI and shoot biomass of relay-cropping soybean at the seedling stage showed an important impact on the recovery growth of soybean after the maize harvested. The correlation analysis showed that:the RGR, NAR and CGR of soybean during the recovery growth period showed significantly positive correlations with the stem diameter, LAI and shoot biomass of soybean when the maize was harvested in the two years and these showed a significantly negative correlations with the plant height and the length of first internode at the same period only in 2013 and also showed some correlations in 2014. This shows that the recovery growth of soybean was closely related to morphologiey, LAI and biomass of soybean when the maize was harvested.5. The yield of maize was increasing with the narrow row distance increasing, but the yield of soybean and LER of the system showed an opposite trend. The resaults showed that the maximum of total yield and LER of the system appeared when the narrow row distance ranging from 20cm to 40cm, and the maximum of yield and LER were 6635.6 kg·hm-2 and 1.60 in 2013 and which were 11044.0 kg·hm-2, 1.81 in 2014. Therefore, the yield and LER of maize and soybean relay intercropping system showed the best performance when the narrow row distance ranging from 20cm to 40cm with the strip width fixed in 200cm.