Productivity of strip intercropping systems in agro-pastoral ecotone

Abstract: Strip intercropping system is not only a technique that achieves high productivity but also an important practice to protect winter and spring wind erosion in Agro-pastoral ecotone. Dry matter accumulation process and yield advantage of intercropping are vital indicators for exploration of intercropping performance and assessing the environmental benefit. This study is aiming to quantify crop growth, yield and land productivity in typical intercropping systems in agro-pastoral ecotone. An expolinear relationship between biomass growth and heat sum of above 0 ℃ temperature was fitted for different crops in the inter- and mono-cropping systems. The regression parameters were used to quantify the delay of crop growth in the intercropping. Land equivalent ratio (LER) was used to explain land productivity and over-yielding of the intercropping systems. The main results showed that sunflower/potato, oats/potato and oats/bean strip intercropping systems with wider width of strips (e.g. 2m:2m intercropping) significantly increased land productivity with yield land equivalent ratio (LER) of 1.12, 1.09 and 1.05, respectively, which means 5 % to 12 % of the land productivity increasing. Intercropping yield advantages were significantly higher in the wider strip intercropping systems than that with narrower ones (1 m:1 m intercropping), and had a less yearly variation. The harvest index (HI) of sunflower was significantly increased in intercropping, while that for other crops were significantly changed. A border row effect was clearly found in the oat based intercropping systems. The border rowers had a significantly higher yield compare to middle rows in the intercrops and sole oats. Strip intercropping decreased the maximum growth rate cm, while the relative growth rate rm stayed as the same as the monoculture. The growth delay of crops in the intercrops was quantified by using the parameter tb, which indicated the thermal time requirement at the time of reaching maximum canopy cover. The growth of five species in the intercropping systems, e.g. sunflower, potato, oats, faba bean and vetch, were delayed 117 to 387 degree days compared to that of monocultures, which resulted 8-26 d of growth delay when we took the daily average temperature (15℃) into accounts. All in all, Strip intercropping systems not only have over-yielding effects and higher economic benefits, especially in intercropping systems with wider strips, but also reduce the agricultural risks in the agro-pastoral ecotone climatically and economically.