Effects Of Density Manipulation And Nitrogen Fertilizer On6Perennial, Cool-season Grasses Seed Production

There is little information available on grass seed production managements in Chinawhere a heavy demand is presented since2000s. From August,2009to July,2013, Weevaluated the influence of climate, seeding rate, row spacing, nitrogen timing and nitrogenrate on Elymus kamoji (ohwi) S.L. Chen, slender wheatgrass (Elymus trachycaulus (Link)Gould ex Shinners ssp. Trachycaulus), smooth bromegrass (Bromus inermisLeyss), Siberianwildrye (Elymus sibiricus L.), Chinese sheepgrass (Leymus chinensis (Trin) Tzvel), and tallfescue (Lolium arundinaceum Schreb.). Most field trial were conducted in Jiuquan in Gansuprovince (the Hexi Corridor), however, we also tested the effect of climate on smoothbromegrass seed yield by conducting the same seeding rate and row spacing experiment inJiuquan (a continental climate with annual precipitation of87mm) and Tongliao (a semiaridcontinental monsoon climate with annual precipitation of362mm). The results indicted that:1. The highest seed yield for Elymus kamoji (ohwi) S.L. Chen, slender wheatgrass,smooth bromegrass, Siberian wildrye, and Chinese sheepgrass were8828kg/hm2,5977kg/hm2,3903kg/hm2,10178kg/hm2, and1980kg/hm2, respectively, which indicted all thefive cool-season grasses have good seed production potential in Jiuquan. If propermanagements was used to improve the utilization rate of the yield potential, such asartificial-aid pollination and lodging control, all the5grasses could have a high actual seedyield.2. Five cool-season, perennial grasses have varied responses to row spacing. Seed yieldfor Elymus kamoji (ohwi) S.L. Chen and smooth bromegrass decreased with increased rowspacing, the highest seed yields were obtained at30cm row spacing treatment, four-yearaccumulated seed yield were6697kg/hm2and4385kg/hm2, respectively. When row spacingincreased from30cm to50cm, four-year accumulated seed yield for slender wheatgrass wasnot influenced, and4-year accumulated seed yield was4390kg/hm2at a row spacing of50cm. Row spacing didn’t have effects on seed yield for Siberian wildrye and Chinesesheepgrass in any year, but weed control at wider row spacing (such as70and90cm) wasdifficult. Thus, a row spacing of50cm seems be optimum for Siberian wildrye and Chinesesheepgrass to maximum seed yield and control weeds. 3. By choosing proper row spacing (such as30cm), high seed yield for smoothbromegrass could be obtained under the climate, soil condition and irrigation system ofJiuquan and Tongliao. The highest4-year and3-year average seed yields are1136kg/hm2and1379kg/hm2in JiuQuan and Tongliao, respectively. However, seed yield would decreasedsignificantly at the second seed production year in Jiuquan and at the third seed productionyear in Tongliao. A better seed development could be achieved in Jiuquan due to the greatersunshine duration and the lower relative humidity during seed mature, and as a result of whichseed quality in Jiuquan is better than Tongliao.4. There was apparent agronomic difference between forage-type and turf-type tallfescue, and the optimum seed production managements varied. Three-year average seedyields for turf-type “Justice” were higher at a greater seeding rate of9kg/hm2and when2/3of the annual nitrogen was applied in autumn. However, seed yields for forage-type “Dovey”were not influenced by seeding rate and nitrogen timing. The optimum nitrogen rate for“Justice” and “Dovey” were190kg/hm2and140kg/hm2, respectively. Under the optimumnitrogen rates, seed yield for “Justice” and “Dovey” were1118kg/hm2and872kg/hm2,respectively. As the interactions of seeding rate, nitrogen rate and nitrogen timing were notsignificant, the optimum seed production management practice for turf-type “Justice” isseeding rate of9kg/hm2+190kg/hm2N with2/3applied in autumn, while for forage-type“Dovey”, management of seeding rate of3kg/hm2+140kg/hm2N would produce more seed,without a significant effect of nitrogen timing.5. Seed yield for smooth bromegrass was influenced significantly by nitrogen rate. Thehighest4-year average seed yield (1084kg/hm2) was obtained at a nitrogen rate of180kg/hm2. If nitrogen rate is greater than180kg/hm2, four-year average seed yield decreasedwith increased nitrogen rate. Nitrogen timing didn’t affect smooth bromegrass seed yield, butthere is a significant effect of nitrogen timing and nitrogen rate. Nitrogen applied in springshould be greater than half of the annual nitrogen rate, otherwise the highest seed yield wouldbe obtained at a nitrogen rate of220kg/hm2resulting in a increase of cost.