Effect of row configuration on yield and radiation use of common vetch-oat strip intercropping on the Qinghai-Tibetan plateau

Abstract

Common vetch (Vicia sativa L.)-oat (Avena sativa L.) intercropping is widely used for forage production, especially in alpine regions. To understand the effects of row configuration on radiation interception and productivity in common vetch-oat strip intercropping under low-input conditions, a field experiment with seven treatments of different numbers of rows for common vetch and oat [1:1 (RI), 2:1 (S21), 3:1 (S31), 3:2 (S32), 4:2 (S42), 4:3 (S43), and 5:3 (S53)] and sole cropping treatments were conducted in the eastern Qinghai-Tibetan plateau (QTP) during 2016 and 2017. Compared with sole cropping, intercropping significantly increased plant height but decreased the net photosynthetic rate (Pn) and the fraction of intercepted photosynthetically active radiation (ƒIPAR) of common vetch in the configurations with narrow strip width such as RI, S21, S31, and S32; as the common vetch strip width increased, their performance tended to be similar with common vetch sole cropping. Plant height, Pn, and ƒIPAR were significantly greater for intercropped oat than oat sole cropping, but decreased as the width of the oat strip increased. On average, intercropping systems improved radiation use efficiency (RUE) by 27 % in comparison to the value expected from the monocultures. The land equivalent ratio (LER) was 1.20 (flowering stage) and 1.14 (maturity stage) on average, and greater than one in all intercropping treatments. Moreover, oat yield in border rows was significantly higher by 41–52 % compared with inner rows, indicating that the border row effect of the dominate crop is a key to increasing yield in common vetch-oat strip intercropping. In order to maximize the utilization of the border row effect, one row or two rows of oat strip which can mitigate intraspecific competition is recommended under low-input conditions. The optimal row configurations RI and S32, which achieved the highest RUE (2.9–3.4 g MJ−1), LER (1.16–1.27), yield (1257−1502 g m-2), and monetary advantage index, can be applied in common vetch-oat strip intercropping for sustainable forage production in alpine regions.