Influence of Row Spacing and P and N Applications on Seed Yield Components and Seed Yield of Siberian Wildrye (Elymus sibiricusL.)

Abstract

Siberian wildrye (Elymus sibiricusL.) is a globally important cool‐season forage grass for semiarid regions. However, its seed yield is often low or inconsistent. As previous studies examined the effects of row spacing and P and N levels on seed production of Siberian wildrye separately, this study was focused on the combined effects of four row spacings (30, 45, 60, 75 cm), four P application levels (0, 60, 90, 120 kg P ha−1), and four N application levels (0, 30, 60, 90 kg N ha−1). Treatments were established within a split‐split‐plot factorial arrangement, with main plots arranged in a randomized complete block design with four replicates. The field experiment was conducted on a Lithic Haprendoll soil type at the Guyuan farm in Hebei Province, China, during the 2010, 2011, and 2012 growing seasons with no supplemental irrigation. Narrow row spacing improved seed yield by increasing fertile tillers m−2, with 30 cm being the optimal row spacing. Phosphorus application increased seed yield by increasing spikelets per fertile tiller, with 90 kg P ha−1being the optimal P application level. Nitrogen application had no significant influence on seed yield in any year. Path analysis structural equation modeling revealed that spikelets per fertile tiller and fertile tillers m−2had significant and direct path coefficients with variances in seed yield. The best management practices for optimal seed yield of Siberian wildrye was 30‐cm row spacing, 90 kg P ha−1, and no additional N beyond 109 g kg−1available soil N under rain‐fed conditions with annual rainfall <300 mm.