Study On Yield And Water And Nitrogn Utilization Of Oat Sole Sowing And Oat/Vetch Mixed Sowing Grassland In Alpine Arid Area

In the desert grassland region of Qinghai-Tibet Plateau,the rainfall was limited and the grassland production and stocking rate are in a relatively low level.Therefore,it is of great of importance to improve agricultural management measures,make full use of natural resources by establishing artificial grassland to promote the development of local livestock production.The objective of this study was to optimize the utilization efficiency of water and nitrogen,a high-yield cultivated grassland management mode in the desert region of the Qinghai-Tibet Plateau was proposed by determining the dry matter yield and crude protein production of artificial grassland and water and nitrogen use efficiency to planting pattern and fertilization level and irrigation mode.The field experiment was conducted in 2017 and 2018 at Jintai Pasture of Wulan county,Qinghai province,which was completely randomized block designed.Two planting patterns were included in the field experiment and which named sole oat P1 and oat/common vetch mixed sowing P2;and establishing two nitrogen fertilization treatments were low level N1(60 kg·N·hm^-2)and high level N2(120 kg·N·hm^-2),respectively.Irrigated respectively by 4 irrigation mode,which was fully irrigated FI?50 mm at tillering stage,jointing stage and flowering stage?,stress at reproductive stage RS?50 mm at tillering stage and jointing stage respectively?,stress at vegetative stage VS?50 mm at flowering stage of oats?and non-irrigated DL.The main results obtained are showed as below:?1?The dry matter yield?DM?could be greatly improved by mixed sowing and increase application fertilization under rain-fed region.Compared with the low-fertilizer treatment,the DM of high-fertilizer treatment at harvest increased by34.7%,9.7%,in 2017 and 2018 respectively.and the crude protein production?CP?increased by41.3%and 20.4%,respectively.Under the mixed sowing treatment,the DM increased by 14.4%and 9.2%and the CP increased by 74.7%and 62.9%compared to the low-fertilizer treatment in 2017 and 2018,respectively.The DM and CP of the P2N2 treatment were the highest among all treatments.In 2017,the DM and CP at the harvest were 10.3 t hm^-2 and 827.2 kg hm^-2 respectively and 7.6 t hm^-22 and 570.2 kg hm^-2 in 2018,respectively.?2?Both the water consumption?WU?and water use efficiency?WUE?of the grassland were enhanced with the increase application of fertilizer under the rain-fed condition.The WU of high-fertilizer treatment was 6.2%and 4.3%higher than that of low-fertilizer treatment in 2017 and 2018,respectively,and the WUE of dry matter(WUE_DM)was increased by 21.0%and 4.9%at harvest in 2017 and 2018,respectively,the WUE of crude protein(WUE_CP)was increased by 30.1%and 17.4%in 2017 and2018,respectively.The WU of the grassland also increased under the mixed sowing treatment with no significant effect on the WUE_DM.but the WUE_CP was also greatly improved.The WU of grassland under the mixed sowing increased by 17.9%and 9.2%in 2017 and 2018,respectively,and the WUE_CP increased by 46.7%and 51.3%compared with sole oat.?3?Under rain-fed conditions,theNO₃^--Ncontent in the high-fertilizer treatment at harvest was higher than that in the low-fertilization was 25.8%and 7.0%in 2017 and2018,respectively,and the nitrogen uptake?NUP?for above-ground grassland in the high-fertilizer treatment was higher than that for low fertilization was 35.8%and 22.4%,respectively.NUP in the mixed sowing grassland treatment was 69.8%and 64.0%higher than of the sole oat treatment,respectively.The nitrogen partial factor productivity?PFPN?in the mixed sowing grassland treatment was 15.8%and 8.3%higher than that of the sole oat treatment,respectively.?4?Under the irrigated conditions,in 2018,the DM at harvest of the FI mode and the RS mode was 61.9%to 81.6%and 40.3%to 48.7%higher than that of the DL mode,respectively,under the same sowing pattern and fertilization level?P<0.05?.There was no significant difference among the treatments except for P1N2 treatment.The highest DM(13.8 t hm^-2)was obtained in the P2N2 FI,flowing was P2N2 RS,the P1N1 DL was the lowest,P2N2 FI was 18.1%and 66.4%higher than that of P2N2 RS and P1N1DL.There was no significant difference in the CP at harvest under the same fertilization level under sole oat conditions.Under the mixed sowing conditions,the CP of FI mode was higher than that in the DL mode?P<0.05?.Compared with the DL mode under low-fertilizer and high-fertilizer levels,the CP increased by 91.4%and 48.9%,respectively,and the FI and the RS mode was no significant difference.The highest CP(850.7 kg ha^-1)at the harvest was obtained in theP2N2 FI,and the flowing was in the P2N2 RS,no difference was found between the two treatments.The lowest CP(293.5 kg ha^-1)was found on the P1N1 DL;P2N2 FI was 1.3%and 189.8%higher than that of P2N2 RS and P1N1 DL.?5?Under the irrigated conditions,the WU of the FI mode and the RS mode was35.4%to 52.2%and 11.9%to 41.6%higher than the DL mode under the conditions of P1N1 and mixed-sowing at harvest in the 2018,respectively?P<0.05?.The WU of the P1N1 VS and P2N2 VS was higher than the DL mode?P<0.05?,the difference between P1N2 and P2N1 was not significant.There was no significant difference in WUE_DM at harvest among the irrigation modes under sole oat conditions.Under the mixed sowing conditions,the WUE_DM of the FI mode was 27.8%to 40.4%higher than the VS mode?P<0.05?,with no significant difference in the RS mode.The highest WUE_DM among all treatments at harvest was obtained in the P2N2 FI,reaching 2.85 kg m^-3,and the following(2.52 kg m^-3)was found in the P2N2 RS.The lowest WUE_DM(1.76 kg m^-3)was found in the P2N1 VS.No significant difference was found in the WUE_CP at harvest under the same sowing pattern and fertilization level.The P2N2 RS treatment had the highest WUE_CP(0.186 kg m^-3),the second was the P2N2 DL,the lowest was found on the P1N1 VS,P2N2 RS was 3.3%and 195.2%higher than the P2N2 DL and P1N1 VS.?6?Under the irrigated conditions,there was no significant difference in NUP under the different irrigation modes under the sole oat conditions in 2018.The NUP of the P2N1 FI was 91.2%higher than that of the P2N1 DL?P<0.05?,no significant different between the two irrigation modes with stress.There was no significant difference between the P2N2 FI and the P2N2 RS,which were higher than the P2N2VS and P2N2 DL?P<0.05?.The P2N2 FI had the highest NUP(136.1 kg kg^-1),and no significant difference compare with the P2N2 RS.A significant difference was found in the PFPN at harvest under the P1N2,P2N1and P2N2 conditions except for the P1N1?P<0.05?.The highest of the PFPN at harvest was observed in the FI mode,higher than the RS mode and the DL,respectively.The highest value of the PFPN(186.1 kg kg^-1)was found in the P2N1 FI treatment,and the flowing was in the P1N1 FI.There was no significant difference in nitrogen production efficiency?PEN?under sole oat and P2N1 conditions at harvest among the irrigated modes.The P2N2 FI was higher than the P2N2 VS and P2N2 DL?P<0.05?.The highest PEN(34.8 kg kg^-1)was obtained in the P1N1 RS,higher than P1N1 FI.In summary,under the condition of rain-fed,the application of mixed sowing and increase application fertilization could increase the forage yield and quality and promote water and nitrogen use efficiency of grassland by decreasing the ineffective evaporation,and enhance the utilization of soil water.Therefore,we recommended that the P2N2 without irrigation condition in the arid alpine area.Under irrigation conditions,the application of irrigation 50 mm at oat tillering and jointing stages under oat/common vetch mixed for high fertilization not only ensured the considerable forage yield and quality at harvest,but also improved the water and nitrogen use efficiency with the increment of the nitrogen uptake.Consequently,the application of irrigation 50 mm at oat tillering and jointing stages could be used as the optimal mode for the cultivation and management of water and fertilizer under irrigation conditions in the desert grassland region of arid alpine area.