| Winter wheat and Alfalfa are the main grain and forage crops on the Dryland of the Loess Plateau.The intercropping of alfalfa and winter wheat has the advantages of complementary utilization of resources and simultaneous harvest of grain and forage.However,the rainfall in the dryland area is insufficient and the annual distribution is uneven.The effect of winter wheat/alfalfa intercropping on the soil water environment is still unclear,the productivity and water use efficiency in the intercropping system have not been quantified.Therefore,the purpose of this study is to determine the growth,dry matter accumulation,yield,soil moisture and water use efficiency of winter wheat/alfalfa intercropping systems and the corresponding monocultures.The field experiment was carried out in Qingyang station of Lanzhou University from October 2017 to October 2019.Randomized block design was applied.Two fertilization rate(high-level,HF,and low-level,LF)and five planting patterns were designed.The planting patterns include sole winter wheat(SW),sole alfalfa(SA),winter wheat/alfalfa 2:1 intercropping(two rows of wheat intercropped with one row of alfalfa,I21),4:2 intercropping(four rows of wheat intercropped with two rows of alfalfa,I42)and 8:4 intercropping(eight rows of wheat intercropped with four rows of alfalfa,I84).There were ten treatments in total,each treatment had three replications.The main results are as follows:(1)Growth performance of winter wheat and alfalfaIn 2018,intercropping promoted the growth of winter wheat,and the plant height and leaf area index of intercropped winter wheat were higher than that of sole cropping under the two fertilization conditions.In the first year of alfalfa cultivation,the alfalfa was weak in competition and the growth rate was slow.In 2019,plant height and leaf area index of intercropped wheat were lower than that of sole wheat,while those of intercropped alfalfa were higher than intercropped alfalfa.In 2018,the dry matter accumulation of winter wheat in I21,I42 and I84 at harvesting increased by 28.3%,11.6% and 14.2%,respectively,compared with that of sole cropping under HF conditions,and by 8.3%,19.0% and 18.0% respectively under LF conditions.In 2019,under both fertilizer treatments,the dry matter accumulation of sole wheat was higher than that of intercropped wheat,but the differences between treatments were insignificant(P>0.05).In 2018,under the two fertilization conditions,the dry matter accumulation of sole alfalfa in the first growth period was higher than that of intercropping treatment,and the dry matter accumulation of I84 was significantly higher than that of I42 and I21(P<0.05),also,the dry matter yield of I84 was higher than that of other treatments in the second branching stage until flowering stage.In 2019,dry matter under HF treatment was generally higher than that under LF treatment.However,the trend of dry matter was similar between the two fertilization modes.The dry matter production of alfalfa in I84 treatment was lower in the first harvesting,but the difference between treatments was not significan in the second harvesting.(2)Crop yield and the land use advantage of intercroppingIn 2018,the total yield of alfalfa in I84 was 24.4%,76.1% and 87.8% higher than those under SA,I21 and I42,respectively,under HF,and those under LF were 25.2%,81.6% and 56.5%,respectively.The total yield of winter wheat of I21 was the highest,which was 52.6%,19.5% and 62.0% higher than that of SW,I42 and I84 under HF conditions,and 50.9%,2.4% and 25.4% higher under LF conditions.In 2019,the total yield of alfalfa in I84 was significantly lower than that under other treatments under two fertilization conditions.The total yield of winter wheat in I21,I42 and I84 was12.5%,30.6% and 14.6% lower than that of SW in under HF conditions;and under LF conditions,the yield in I21 and I42 was not significantly different from that of single cropping wheat,but significantly higher than that of I84.In 2018,the winter wheat/alfalfa intercropping system showed land use advantage,with land equivalent ratio(LER)ranged between 1.04 and 1.23.In all intercropping systems,winter wheat LER was greater than 0.5,indicating that winter wheat was more competitive than alfalfa.In 2019,the LER of all intercropping systems under HF treatment was less than or equal to 1.0,while under LF treatment I21 and I42 showed intercropping advantage with LER of 1.13 and 1.05 respectively.(3)Soil water content and water use efficiencyAt wheat harvesting in 2018,the average soil water content in 0-200 cm layer i nI21,I42 and I84 under HF conditions was 23.8%,19.7% and 18.6% lower than SA,and the soil moisture content under LF conditions was 21.8%,16.9% and 14.8%lower,respectively.At harvesting of alfalfa,SA had the lowest soil moisture content in the 0-200 cm layer under both high and LF conditions,SW hold the highest soil water content.In 2019,the water consumption of sole winter wheat under the condition of HF was higher,and its soil moisture content was significantly lower than that of intercropping systems,while the difference between treatments under the condition of LF was not significant(P>0.05).At the harvesting of alfalfa,there was no significant difference in soil water content between monocropped plots and intercropped plots(P>0.05).The water consumption of intercropping population was less than the weighted average of sole crops.In 2018,intercropping I21,I42 and I84 improved crop water use efficiency compared with monocropped alfalfa and wheat.In 2019,the WUE of I21,I42 and I84 was higher than that of monoculture wheat,but lower than that of alfalfa monoculture.Under the condition of LF,the water use advantage of intercropping group was more prominent than that of sole crops.In conclusion,intercropping of winter wheat and alfalfa had the potential to improve the system yield.The land use advantage of intercropping was between4%-23% in the first year compared with sole crops,and the land use advantage was also shown in the second year under LF treatment.In the first year,the water use efficiency in intercrops was also significantly higher than that of the sole crops.However,in the second year,only I42 under the condition of HF and I21 under the condition of LF showed the advantage of water use efficiency.The rainfall during the experiment was much higher than the long-term average rainfall,so the yield and water use advantage of the intercropping population should be further studied under different rainfall patterms. |
