Abstract:

This research aimed to identify a suitable planting pattern for oilseed flax production in a dry-farming region. A long-term field experiment was started in 2012 with a 4-year crop rotation cycle， designed to measure the effects on flax crop performance of previous crop， and various patterns of flax planting interval within the four-year rotation， compared with continuous flax cropping. Crop parameters measured included plant height， stem diameter， dry matter accumulation and distribution， and the experiment included six different crop rotation patterns： Flax→flax→flax→flax ［（F）FFF］； Flax→wheat→potato→flax ［（F）WPF］； Flax→potato→flax→wheat ［（F）PFW］； Flax→flax→wheat→potato ［（F）FWP］； Flax→wheat→flax→potato ［（F）WFP］ and flax→wheat→potato→wheat ［（F）WPW］. Results for the ninth year showed significantly increased grain yield （29.89%-109.57%） in crop rotation treatments compared with continuous cropping of oilseed flax. The ranking of the six tested rotations for yield was： （F）WPW>（F）FWP>（F）WFP>（F）PFW>（F）WPF>（F）FFF. The grain yield of oilseed flax was significantly affected by previous crop， frequency and years interval of flax cropping and number of years of continuous flax cropping. Yield was increased by 54.45%-59.29% under wheat stubble and potato stubble compared with oilseed flax stubble， and increased by 30.66% and 109.57%， respectively， under 50% and 25% frequencies， compared with 100% frequency. The grain yield of oilseed flax under two-year continuous cropping was higher by 29.89% than four-year continuous cropping， and increased with increase in years interval between flax crops. Correlation analysis identified a significantly positive correlation between oilseed flax grain yield and effective capsule number， branch number and 1000-seed weight. The effective capsule number， branch number and 1000-seed weight of oilseed flax under rotation treatment were increased by 35.88%-108.91%， 15.47%-46.19% and 14.61%-16.34%， respectively （P<0.05）， compared with continuous cropping. In addition， the high grain yield of oilseed flax was accompanied by an increase in plant height， stem diameter and dry matter accumulation and these increases were， respectively， 5.11%-42.24%， 2.77%-39.92% and 31.25%-117.89% under the rotation regimes， compared with continuous cropping. Reduction in the number of years of continuous cropping years， change of crop stubble， decreased flax planting frequency and increased of interval between flax crops also improved flax crop performance. In summary， crop rotation improved the vigor of oilseed flax， resulting in greater plant height and stem diameter， improved dry matter accumulation and distribution， leading to increased branch number， effective capsule number and 1000-seed weight， and increase in the crop yield of oilseed flax. The results indicated that a multiple-crop rotation pattern was an effective way to avoid the yield reduction caused by continuous cropping in oilseed flax. The rotation： Flax→wheat→potato→wheat performed best among those tested and can be recommended as an appropriate cropping rotation for oilseed flax production in the dry region of northwest China.

Key words: oilseed flax, crop rotation, previous crop, crop frequency, crop interval, dry matter, yield