Pastures in integrated crop/livestock production systems © 2013 Proceedings of the 22 nd International Grassland Congress 982 Relation of residue biomass after defoliation to regrowth dry matter, WSC and grain yield of winter wheat Lihua Tian A , Qingping Zhang A , Yuanbuo. Liu A , Yuying Shen A , Lindsay W Bell B and Jeremy PM Whish B A The State Key Laboratory of Grassland Agro-ecosystems, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou 730020, People’s Republic of China, www.lzu.edu.cn B CSIRO Ecosystems Sciences/APSRU, PO Box 102, Toowoomba, QLD 4350, Australia . Contact email: tianlh08@lzu.edu.cn Keywords: Loess plateau, rain-fed region, cutting, yield components. Introduction The importance of defoliation height on final yield in dual- purpose wheat is inconsistent. In one study no difference in final wheat yield following a severe grazing at 2 cm compared to light grazing at 6 cm was found (Dann et al. 1983). In contrast, clipping at 3 cm above ground level significantly reduced grain yield compared to 7 cm (Arzadun et al. 2006). An explanation for these inconsistent results may be an underestimation of the value of the remaining biomass and its role in the regrowth process (Fulkerson and Donaghy 2001). In this study, the percentage of residue biomass remaining after defoliation was considered when examining the effect of defoliation height on dry matter accumulation and water-soluble carbohydrate (WSC) during wheat regrowth on the Loess plateau, China. Methods The experimental trial was established at Qingyang Loess Plateau Research Station of Lanzhou University (35°40 N, 107°52 E; altitude 1298 m a.s.l.) in Gansu Province of China. Agriculture in this area is rain-fed with summer- dominant rainfall. Wheat (Triticum aestivum) was sown on 20 September 2010 (cv. Longyu 216). Four treatments with an uncut control and 3 defoliation treatments (Light defoliation, Moderate defoliation and Severe defoliation) were imposed at tillering (7 April 2011) with 81%, 45% and 0% of the total biomass left for regrowth, respectively. Treatments were arranged in a randomised complete block design with 4 replicates; the plot size was 3 m by 3 m. Dry matter was compared between the treatments at 3 crop stages (booting, anthesis and maturity) by sampling 3 rows (1 m×0.15 m×3) from the centre of each plot. At crop maturity, total grain yield and yield components (spike number per m 2 , grain number per spike and kernel weight) were measured. Water-soluble carbohydrate (WSC) within the plant at booting and anthesis were analysed by the anthrone method (Yemm and Willis 1954). Results and Discussion DM dynamic of regrowth Following defoliation, the dry matter accumulation at booting of the light defoliation treatment was 17% higher than the uncut control, while both the moderate and severe defoliation produced less biomass than the uncut control, 26% and 58% (P<0.05), respectively. At anthesis, this relationship remained unchanged, the light defoliation treatment had accumulated 13% more biomass and the moderate and severe defoliation treatments accumulated 8% and 42% (P<0.05) less biomass than the uncut control (Table 1). WSC concentration and storage at booting and anthesis During regrowth, there was no significant difference between defoliation treatments in the WSC concentration at booting; at anthesis, a similar trend occurred apart from the severe defoliation treatment that had an increased WSC concentration. With respect to WSC storage (total DM multiplied by the WSC concentration), the light defoliation increased the WSC storage as a result of the increased DM production at both booting and anthesis. For the moderate and severe defoliation, the WSC storage at booting was reduced by 12% (P>0.05) and 55% (P<0.05), but at anthesis, the reduction was less (8% and 14%, respect- ively), as the DM accumulation had caught up and WSC concentration was slightly increased. Table 1. Regrowth of DM at booting and anthesis under different defoliation treatments (mean±se). Defoliation intensity Residue DM (t/ha) Booting (t/ha) Anthesis (t/ha) Uncut control 1.01 ± 0.16 3.13 ± 0.37 5.45 ± 0.27 Light 0.82 ± 0.04 3.66 ± 0.60 6.17 ± 0.27 Moderate 0.55 ± 0.06 2.31 ± 0.30 5.02 ± 0.24 Severe 0 1.30 ± 0.20 3.16 ± 0.07 LSD(P=0.05) 0.27 1.23 0.70 brought to you by CORE View metadata, citation and similar papers at core.ac.uk provided by University of Kentucky