Malhi, S. S.

Nyborg, M.

English

University of Kentucky

University of Kentucky UKnowledge International Grassland Congress Proceedings 21st International Grassland Congress / 8th International Rangeland Congress Long‐Term Effects of Annual Applications of N and S Fertilizers to Grassland on Forage Yield, Rootmass, and Soil pH, Organic C and N on a Dark Gray Chernozem in North‐Central Saskatchewan S. S. Malhi Agriculture and Agri‐Food Canada, Canada M. Nyborg University of Alberta, Canada Follow this and additional works at: https://uknowledge.uky.edu/igc  Part of the Plant Sciences Commons, and the Soil Science Commons This document is available at https://uknowledge.uky.edu/igc/21/2-3/12 The 21st International Grassland Congress / 8th International Rangeland Congress took place in Hohhot, China from June 29 through July 5, 2008. Proceedings edited by Organizing Committee of 2008 IGC/IRC Conference Published by Guangdong People's Publishing House This Event is brought to you for free and open access by the Plant and Soil Sciences at UKnowledge. It has been accepted for inclusion in International Grassland Congress Proceedings by an authorized administrator of UKnowledge. For more information, please contact UKnowledge@lsv.uky.edu. 　 Multifunctional Grasslands in a Changing World 　 Volume Ⅰ 　 瞯 ]407　 瞯Grasslands/Rangelands Resources and Ecology ——— Soil Quality and Plant NutritionLong‐term effects of annual applications of N and S fertilizers to grassland on forage yield , rootmass , and soil pH , organic C and N on a Dark Gray Chernozem in north‐central SaskatchewanS . S . Malhi１ and M . N yborg２１ A griculture and A gri‐Food Canada , P .O . Box １２４０ ,Mel f ort , Saskatchew an , Canada S０E １A０ (Phone : ３０６‐７５２‐２７７６Ext ２３０ ; Fax : ３０６‐７５２‐４９１１ ; E‐mail ;malhis ＠ agr .gc .ca ) ; and ２ Department o f Renew able Resources , University o fA lberta , Edmonton , A lberta , CanadaKey words : Forage yield , N and S fertilization , plant species composition , soil organic C and N , soil pH , soil qualityIntroduction Many soils in the Parkland region of Prairie Provinces of Canada contain insufficient amounts of both plant‐available N and S for high crop yields . Application of N and/or S fertilizers on grasslands can acidify soil or alter some othersoil properties , but also improve soil quality ( Malhi et al . １９９１) . The objective of this study was to determine the effects of long‐term N , S and/or K fertilization on forage dry matter yield (DMY) , root mass , plant species composition , and soil pH , total organicC ( TOC) and N ( TON) , and light fraction organic C ( LFOC) and N ( LFON) .Materials and methods A field experiment on a perennial grass stand was conducted from １９８０ to ２００５ on a Dark GrayChernozem (Boralfic Boroll ) loam soil at Canwood in north‐central Saskatchewan , Canada ( mean annual precipitation ４２５mm) . The site had been under annual crops for several years in １９２０摧s or early １９３０摧s , and then allowed to revert to grassland .The dominant grasses at the start of experiment were bromegrass ( Bromus inermis Leyss) , Kentucky bluegrass ( Poa p ratensisL .) and rough hair grass ( A grostic scabra Wild) . There were five annual fertilizer treatments : １ . no fertilizer ( Nil) , ２ . １１２kg N ha‐１ （N) , ３ . １１ kg S ha‐１ （S) , ４ . １１２ kg N ＋ １１ kg S ha‐１ （NS) , and ５ . １１２ kg N ＋ １１ kg S ＋ ４０ kg K ha‐１ （NSK ) .Forage was usually harvested once in each growing season for determination of DMY . Plant species composition in １９９４ wasestimated using ground cover method . Soil samples in Nil , N , S , NS or NSK treatments were obtained at ５ or ７ .５ cm intervalsfrom the ０‐１５ and １５‐３０ cm depths in different years for pH , bulk density , and total and light fraction organic C and N . Rootmass was estimated by digging out soil from the ０‐１５ cm depth .Results and discussionDry Matter Yield (DMY) and Root Mass Except in some years , application of N fertilizer increased DMY only slightly over theNil treatment . The DMY was increased considerably with combination of N and S fertilizers ( i .e . , NS treatment ) . Thisindicated that the response of hay yield to N was impeded by S deficiency in soil , and application of N together with S was aneffective way for increasing DMY . However , application of K in addition to N and S fertilizers only had moderate effect onincreasing DMY . Like DMY , root mass was greatest in treatments receiving both N and S fertilizers .Plant Species Composition The composition of plant species changed markedly in various fertilizer treatments after long‐termfertilization . In the Nil treatments , land was covered with bromegrass , fine grasses and herbs ( dogwood ) . The S onlytreatment had vegetation generally similar to Nil , with slightly more vetches . In the N only treatment , the vegetation changeddramatically and there was virtually no bromegrass in the stands . The grass stand changed towards increasing predominantlybromegrass with combined applications of NS or NSK . Bromegrass is a higher yielding species than other grasses , which mayhave contributed to increased forage DMY due to combined N and S fertilization compared to other species .Soil pH Soil pH in the surface soil layer was substantially decreased with annual applications of N and S fertilizers . Thedecrease in soil pH was more when only N fertilizer was applied compared to both N and S fertilizers together . In the ５‐１０ cmlayer , there was some depression in soil pH in the N alone treatment . In the deeper soil layers , soil pH tended to increase withN or NS fertilization in most cases , probably due to downward movement of Ca or other bases to these soil layers .Organic C and N Storage in Soil Total organic C and total N in soil increased with annual applications of N and S fertilizerstogether ( NS treatment) . Annual applications of NS fertilizer treatments increased both LFOC and LFN considerably in thesurface soil layer . The NS treatment also increased LFOC and LFN in deeper layers . The increase due to NS application forLFOC as a percentage of TOC and for LFN as a percentage of TN indicated that application of N and S fertilizer could markedlyincrease light fraction of C and N sequestrated in soil , most likely due to increase in root mass from balanced fertilization ( Malhiand Gill ２００２) .Conclusions Forage DMY increased considerably with combined application of N and S fertilizers and further improved when Kfertilizer was also applied ( NSK) , while N or S alone had limited effect on the DMY on this soil deficient in both available Nand S . Annual applications of N and S fertilizers reduced soil pH in the top １０ cm soil , mainly in the ０‐５ cm layer , while therewas a tendency for increase in soil pH in some deeper soil layers . Mass of TOC , TN , LFOC and LFN in the ０‐１５ cm soilincreased with NS application . There was a close relationship between DMY improvement and increase in C storage in soil fromproper fertilization . The findings suggest that application of balanced fertilization by alleviating all nutrient deficiencies is anappropriate strategy for sustaining high forage yield and increasing C and N sequestration in soil .

Long‐Term Effects of Annual Applications of N and S Fertilizers to Grassland on Forage Yield, Rootmass, and Soil pH, Organic C and N on a Dark Gray Chernozem in North‐Central Saskatchewan

https://uknowledge.uky.edu/cgi/viewcontent.cgi?article=2574&amp;context=igc

Long‐Term Effects of Annual Applications of N and S Fertilizers to Grassland on Forage Yield, Rootmass, and Soil pH, Organic C and N on a Dark Gray Chernozem in North‐Central Saskatchewan

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