Effects Of Different Planting Patterns And Fertilization Gradients On Root Characteristics Of Three Forage Grasse

The plant root system is the main part for absorption,transformation and nutrient storage,and has a key influence on the growth,development and morphological composition of the above-ground parts of the plant.Investigating the effects of different planting ways and fertilization gradients on forage root trait can provide a basis for agricultural production and efficient planting of artificial grassland,and provide a reference for high forage yield and efficient land utilization.In this paper,alfalfa（Medicago sativa）,duckweed（Dactylis glomerata）,and chicory（Cichorium intybus）were used as the material,and six planting ways were carried out in a completely randomised group design,included alfalfa monoculture（SM）,duckweed monoculture（SD）,chicory monoculture（SC）,alfalfa intercropped with duckweed（DM）,duckweed intercropped with chicory（CD）and alfalfa intercropped with chicory（CM）,and five fertilization gradients,included CK-0 t·hm^-2,T₁-10 t·hm^-2,T₂-20 t·hm^-2,T₃-30 t·hm^-2,T₄-40 t·hm^-2.The morphological characteristics of the root systems of different forage grasses,the rates of above-ground and root biomass allocation and the response of root trait to planting ways and fertilization gradients were investigated.The main results showed:（1）There are significant differences in root traits among the three types of forage under different planting methods and fertilization gradients.Under T₃ treatment and chicory+alfalfa（CM）intercropping,the total root length,root surface area,average root diameter,and root volume of chicory were significantly increased compared with those of single seeding（P（27）0.05）.Under T₄ treatment,the total root length,average root diameter and root volume of duckweed+Alfalfa（DM）were significantly increased compared with those of monoculture（P（27）0.05）.The total root length,root surface area,average root diameter and root volume of intercropped alfalfa were significantly lower than those of monocropped alfalfa（P（27）0.05）.（2）Under the six different planting ways,the root crown allometric growth indexαwas greater than 1 for forage grasses except for the root crown allometric growth indexαwas smaller than 1 for monosown duckweed（SD）and alfalfa+chicory（CM）,but there was no significant difference in root crown allometric growth index between the different planting ways.The root crown allometric growth indexαwas greater than 1 in chicory.The root crown allometric growth index of alfalfa was greater than 1 except CK treatment.The above-ground and below-ground biomass allocation rates of duckweed differed significantly between fertilizer treatments,with the T₃ treatment being the most favourable for root growth.（3）In contrast to monoculture forage,intercropping with alfalfa significantly increased the soil ammonium nitrogen content compared to monosown forage,and the root trait of chicory and duckweed showed a highly significant positive correlation with soil ammonium nitrogen content（P（27）0.01）.Alfalfa root trait showed a highly significant positive correlations with soil effective phosphorus,and significant and highly significant negative correlations with soil p H（P（27）0.01）.Under different fertilization gradients,all three forage grasses showed significant and highly significant positive correlations between root trait and soil effective phosphorus,among which duckweed showed a highly significant positive correlations between root trait and soil ammonium nitrogen（P（27）0.01）.In summary,in the intercropping with alfalfa,the root morphological parameters of duckweed and chicory were improved,which was superior to other planting ways.Fertilization could promote the growth and development of forage roots,and the optimal fertilization amount for duckweed and chicory is T₃-30 t·hm^-2.At the same time,increasing soil ammonium nitrogen and available phosphorus content,reducing soil bulk density,could significantly promote grass root growth.