Crop rotation as a tool towards sustainable barley cropping

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http://urn.fi/URN:ISBN:978-951-51-1607-9
Title: Crop rotation as a tool towards sustainable barley cropping
Author: Zou, Ling
Other contributor: Helsingin yliopisto, maatalous-metsätieteellinen tiedekunta, maataloustieteiden laitos
Helsingfors universitet, agrikultur-forstvetenskapliga fakulteten, institutionen för lantsbruksvetenskaper
University of Helsinki, Faculty of Agriculture and Forestry, Department of Agricultural Sciences
Publisher: Helsingin yliopisto
Date: 2015-10-23
Language: en
Belongs to series: URN:ISSN:2342-5423
URI: http://urn.fi/URN:ISBN:978-951-51-1607-9
http://hdl.handle.net/10138/156605
Thesis level: Doctoral dissertation (article-based)
Abstract: Factors limiting barley yield have been reduced since the Green Revolution globally. Nevertheless, higher yields are pursued with the pressure to feed the increasing human population and domestic animals. However, sustainability can be impaired by the cereal monocultures, in particular, cereal-specific pathogen inocula can increase at the cost of diversity of soil microfauna. Use of pesticides has selected for resistance in weeds and pathogens. Use of mineral fertilizers has resulted in waste of resources and pollution. In Finland, about half of the arable land is used for continuous cereal production, and barley (Hordeum vulgare), as an important source for food and feed, is the most cultivated cereal crop. In this dissertation, research focused on evaluating the effects of various rotation crops on weeds, pathogenic fungi, soil fertility and yield of subsequent barley. The competitive ability of six crops, namely buckwheat (Fagopyrum esculentum), caraway (Carum carvi), faba bean (Vicia faba), hemp (Cannabis sativa), common vetch (Vicia sativa) and white lupin (Lupinus albus) with weeds was evaluated in glasshouse and field experiments. In the glasshouse experiment, couch grass (Elymus repens) grown with buckwheat accumulated the least dry matter. Activated charcoal was used to exclude the effect of root exudates from donor crops. The results indicated that activated charcoal incorporated in the soil deactivated buckwheat root exudates that apparently inhibited the growth of couch grass. In the field experiment, buckwheat s fast growth and formation of effective leaf area inhibited growth of weeds most effectively among the crops tested. The effect of turnip rape [Brassica rapa L. ssp. oleifera (DC.) Metzg.] on several soil pathogenic fungi was evaluated in a field trial in two growing seasons involving five different cultivation regimes: mixed culture of barley and turnip rape, turnip rape sown after barley, and turnip rape incorporated as green manure either in autumn or in spring, with continuous barley monoculture as a control. Soil fungal community structure was monitored with capillary-based LH PCR of the ITS region using primers ITS1F/ITS4. The mixed culture and sowing turnip rape after barley did not significantly decrease the relative abundance of Fusarium spp. Incorporation of turnip rape plants into the soil, as a source of organic matter and nutrients, was associated with a low relative abundance of Fusarium spp. Fungal diversity was the lowest and the relative abundance of Fusarium spp. the highest in continuous barley. Higher fertilizer application and organic matter incorporation, leading to high fungal diversity, seemed more important in affecting Fusarium spp. than the allelochemicals of turnip rape, as turnip rape extracts did not detectably inhibit the growth of F. culmorum in an in vitro test. In growth media of different nutrient levels, 10 g soil were suspended in 100 mL sterile water, then 400 μL of the suspended solution was spread on the media of each nutrient level with four replicates. The number of fungal colonies was counted. The soil Fusarium CFU count was higher on nutrient-poor growth medium than on rich medium, supporting the results of field experiments. Results of sequencing indicated that Penicillium spp. might also tolerate low nutrient availability. In two experiments that ran 2010-2012 and 2011-2013, faba bean, turnip rape and barley were sown as first crops and their residues were tilled into the soil after harvest in blocks in the first year. In the following year, barley, buckwheat, caraway, faba bean, hemp and white lupin were sown in each block and incorporated either at flowering stage (except barley) or after harvest. Barley yield and grain protein concentration were determined. Mineral N concentrations in the plough layer two months after incorporation of crops and before sowing barley in the following spring were determined. In the third year, all the plots were sown with barley. The beneficial effect of faba bean and turnip rape, as first crops, on yields and grain protein concentration of barley was still detectable in the third year. Barley yields after white lupin, faba bean and hemp, as second crops, were higher than in continuous barley. Barley grain protein concentration was increased after faba bean. In contrast, barley yield and grain protein concentration were not improved after buckwheat and caraway. Incorporation of plants at flowering stage posed a risk of increased N leaching, suggesting that incorporation of plants should be delayed or catch crops should be used during winter to reduce N leaching. The response of barley yields to increased mineralized N from green manure or residues after harvest of rotation crops was significant only in the first experiment conducted in 2010-2012 suggesting that increased mineral N in the plough layer has minor influence on barley yield. Thus, rotation with faba bean, white lupin and hemp was beneficial to barley grain yield. In addition, barley grain protein concentration was increased after rotation with faba bean. Weed growth was most strongly suppressed by buckwheat as a complement to current weed management regime, but, rotation with buckwheat and incorporation of its residues did not improve the yield of the successive barley. The effect of glucosinolates of turnip rape on soil-borne pathogens was outweighed by high fungal bio-diversity suggesting that allelochemicals released from plants sown at a realizable density in the field are unlikely to control pathogens. Maintaining high microbial diversity through sufficient nutrient input is crucial to control pathogenic Fusarium spp. populations.Yhä intensiivisempi kasvintuotanto on johtanut lisääntyneeseen viljojen monokulttuuriviljelyyn, jolla voi olla negatiivinen vaikutus kestävään tuotantoon. Erityisesti viljoille spesifien kasvipatogeenien määrä voi lisääntyä. Lisääntynyt torjunta-aineiden käyttö on jo johtanut rikkakasvien ja patogeenien resistenttien kantojen syntyyn. Lisäksi teollisten lannoitteitten käyttö on johtanut luonnonvarojen tuhlaukseen sekä ympäristön saastumiseen. Suomessa noin puolella viljelykelpoisesta alasta viljellään viljoja, ja tärkeä ruoka- ja rehukasvi ohra (Hordeum vulgare) on viljellyin laji. Tässä väitöskirjatyössä tutkittiin erilaisten viljelykiertojen vaikutusta rikkakasveihin, patogeenisiin sieniin, maan viljavuuteen sekä satotasoon ohralla. Tutkimuksen tulokset osoittivat, että ohran jyväsato kasvoi viljeltäessä ohraa viljelykierrossa härkäpavun (Vicia faba), valkolupiinin (Lupinus albus) tai kuituhampun (Cannabis sativa) kanssa. Lisäksi ohran jyvän proteiinipitoisuus kasvoi viljeltynä härkäpavun jälkeen. Tattari (Fagopyrum esculentum) esti parhaiten rikkakasvien kasvua, mutta viljelykierto sen kanssa ei kuitenkaan nostanut seuraavan vuoden ohrasatoa. Rypsin glukosinolaattien vaikutus maalevintäisten patogeenien määrään ei ollut odotettu, mutta sen sijaan maaperän sienien biodiversiteetti oli runsas. Nämä tulokset antavat viitteitä, että peltoon kynnetystä kasvijätteestä erittyneet allelokemikaalit eivät todennäköisesti pysty torjumaan patogeenejä. Sen sijaan maaperän runsaan mikrobien monimuotoisuuden ylläpitäminen riittävällä ravinnetasolla, joka lisääntyi käytettäessä rypsiä viherlannoitteena, on tärkeää Fusarium spp. sienten torjumisessa.
Subject: Plant Production Biology
Rights: Julkaisu on tekijänoikeussäännösten alainen. Teosta voi lukea ja tulostaa henkilökohtaista käyttöä varten. Käyttö kaupallisiin tarkoituksiin on kielletty.


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