Root distribution and morphology of maize seedlings as affected by tillage and fertilizer placement

Suboptimal soil conditions are known to result in poor early growth of maize (Zea mays L.) in no-tillage (NT) systems in contrast with conventional tillage (CT) systems. However, most studies have generally focused on maize roots at later growth stages and/or do not give details on root morphology. In a 2-year field study at two locations (silt loam and loam soils) in the Swiss midlands, we investigated the impacts of tillage intensity, NT vs. CT, and NP-fertilizer sidebanding on the morphology, vertical and horizontal distribution, and nutrient uptake of maize roots at the V6 growth stage. The length density (RLD) and the length per diameter-class distribution (LDD) of the roots were determined from soil cores taken to a depth of 0.5 m and at distances of 0.05 and 0.15 m from both sides of the maize row. The temperature of the topsoil was lower, and the bulk density and penetration resistance were greater in the topsoil of NT compared with CT. The growth and the development of the shoot were slower in NT. RLD was greater and the mean root diameter smaller in CT than in NT, while the vertical and horizontal distribution of roots did not differ between CT and NT. RLD increased in the zone enriched by the sidebanded fertilizer, independent of the tillage system, but LDD did not change. The poorer growth of the roots and shoots of maize seedlings was presumably caused by the lower topsoil temperature in NT rather than by mechanical impedance. The placement of a starter fertilizer at planting under NT is emphasize

Interactions of maize and Italian ryegrass in a living mulch system: (2)Nitrogen and water dynamics

Water and nitrogen availability may limit the growth of the main crop competing with a cover crop in a living mulch system. Some aspects of the dynamics of water (soil water content and deep percolation) and nitrogen (concentration in soil solution and leachate) were studied in maize (Zea mays L.) sown into a bare soil (BS, conventional cropping) or into a living Italian ryegrass (Lolium multiflorum Lam.) mulch (LM) during three years. Eight lysimeters (1.0 by 1.0m square surface area and 1.1m deep) with ceramic suction cups, TDR probes and a drainage pipe were used each. In LM a 0.3m wide strip was kept free of grass around the maize row. The living mulch reduced the soil water content between 0.3 and 0.9m soil depth, which remained lower even after intense rainfall. Deep percolation over the entire maize crop season was at least 40% lower in the LM compared to the BS treatment. In LM the nitrate concentrations in the soil solution and in the leachate (usually <10mgL−1) were very low. In BS the nitrate concentration in the leachate reached as much as 70mgL−1. Losses of N in LM did not reach 1% of the values observed in BS. Reduced water and N availability in LM contribute to explain the decrease in growth and yield of the maize plants, and are in good agreement with the dense root system developed in this cropping system as compared to BS. The challenge for the development of living mulch systems is to improve the uptake of water and nitrogen by the roots of the main crop in a competitive environment without affecting the capacity of the cover crop to prevent N losses by leachin

Assimilate transport in maize (Zea mays L.) seedlings at vertical low temperature gradients in the root zone

Even moderate chilling temperatures may cause important modifications in assimilate movement in maize seedlings from the shoot to the roots, but there is no information on long-distance transport of assimilates in plants subjected to vertical gradients of moderately low temperatures in the root zone. Seedlings of a chilling-tolerant (KW1074) and a chilling-sensitive inbred line (CM109) of maize were grown in a system that allowed the maintenance of temperature gradients between the topsoil (0-10 cm) and the subsoil (10-50 cm). After pregrowth at 24°C until the thirdleaf stage, plants were subjected to chilling-stress regimes for 6 d (17/17/17 °C, 17/17/12°C, 12/12/12°C, 12/12/17°C, air/topsoil/subsoil). The time taken for the assimilates to enter the phloem from the second leaf increased at low temperatures for both lines, but to a much greater extent in CM109. Although mainly influenced by air and topsoil temperature, low temperature in the subsoil also affected this trait in CM109. The speed of assimilate transport between the second leaf and the mesocotyl in KW1074 was strongly reduced by cool temperatures in the shoot and topsoil as well as by 12°C in the subsoil in CM109, because the latter line had a larger portion of its root system in the subsoil as compared to KW1074. The portion of assimilates allocated to the root decreased at low temperatures in both lines, but to a greater extent in CM 109, and was controlled mostly by the subsoil temperature. After rewarming, values of all measured parameters of assimilate transport returned to near pregrowth levels within a few day

Stickstoffausnutzung, Beikrautregulierung und Erträge unterschiedlicher Bestellverfahren

In a field trial of several years duration, an organic cultivation technique (BIO) was compared to ploughing, shallow tillage and no tillage. In the case of BIO, soil tillage was accomplished both by ploughing (prior to maize) and by mulch seeding (prior to cereals). The maize yields of the various techniques showed no significant differences in the case of slurry application. BIO-wheat yielded slightly lower in certain years, a fact attributable to low plant density. Wide spacing between rows (25 cm) and hoeing of the cereals enabled mulch seeding without weed-regulation problems in the case of BIO. Where slurry fertiliser was applied, the apparent nitrogen utilisation of the plants – despite application via an umbilical-hose spreader – was low, with values of 30-70%. Clearly, significant unused potential lurks here

Root development and heavy metal phytoextraction efficiency: comparison of different plant species in the field

Heavy metal phytoextraction is a soil remediation technique which implies the optimal use of plants to remove contamination from soil. Plants must thus be tolerant to heavy metals, adapted to soil and climate characteristics and able to take up large amounts of heavy metals. Their roots must also fit the spatial distribution of pollution. Their different root systems allow plants to adapt to their environment and be more or less efficient in element uptake. To assess the impact of the root system on phytoextraction efficiency in the field, we have studied the uptake and root systems (root length and root size) of various high biomass plants (Brassica juncea, Nicotiana tabacum, Zea mays and Salix viminalis) and one hyperaccumulator (Thlaspi caerulescens) grown in a Zn, Cu and Cd contaminated soil and compared them with total heavy metal distribution in the soil. Changes from year to year have been studied for an annual (Zea mays) and a perennial plant (Salix viminalis) to assess the impact of the climate on root systems and the evolution of efficiency with time and growth. In spite of a small biomass, T. caerulescens was the most efficient plant for Cd and Zn removal because of very high concentrations in the shoots. The second most efficient were plants combining high metal concentrations and high biomass (willows for Cd and Zn and tobacco for Cu and Cd). A large cumulative root density/aboveground biomass ratio (LA/B), together with a relative larger proportion of fine roots compared to other plants seemed to be additional favourable characteristics for increased heavy metal uptake by T. caerulescens. In general, for all plants correlations were found between L A/B and heavy metal concentrations in shoots (r=0.758***, r=0.594***, r=0.798*** (P<0.001) for Cd, Cu and Zn concentrations resp.). Differences between years were significant because of variations in climatic conditions for annual plants or because of growth for perennial plants. The plants exhibited also different root distributions along the soil profile: T. caerulescens had a shallow root system and was thus best suited for shallow contamination (0.2 m) whereas maize and willows were the most efficient in colonising the soil at depth and thus more applicable for deep contamination (0.7 m). In the field situation, no plant was able to fit the contamination properly due to heterogeneity in soil contamination. This points out to the importance and the difficulty of choosing plant species according to depth and heterogeneity of localisation of the pollutio

DOK-Versuch: Nährstoffversorgung in Winterweizen – Wo wird es eng?

Das Ziel des seit 1978 durchgeführten DOK-Systemversuchs in Therwil BL ist der Vergleich zwischen einem biologisch-dynamischen (D), einem organisch-biologischen (O), einem konventionellen (K; organisch-mineralische Düngung) und einem konventionell-mineralischen (M; ausschliesslich mineralische Düngung) Anbausystem im Hinblick auf nachhaltigen Pflanzenbau und Bodenfruchtbarkeit. Der Versuch verfügt über zwei Düngungsniveaus (Tab. 1) und erlaubt die Untersuchung der Einflüsse unterschiedlicher Nährstoffversorgung auf die Ertragsbildung und Aussagen zu Limitierungen einzelner Pflanzennährstoffe

Laufkäfer in der Aare-Aue Rupperswil, Kanton Aargau, in den ersten fünf Jahren nach der Renaturierung (Coleoptera, Carabidae)

Ground beetles of the alluvial area Rupperswil, Canton Aargau, Switzerland, during the five years after its restoration (Coleoptera, Carabidae) The Rupperswil floodplain (Canton Aargau) was restored in the years 2010–2011. From 2012 to 2016, annual surveys of ground beetles were conducted. Over the five years, a total of 116 species were collected. From these species, 12 are classified as threatened, near threatened, or rare according to the Red List of Switzerland. Moreover, considerable numbers of Bembidion atrocaeruleum, B. prasinum, and Harpalus progrediens were found in the Rupperswil floodplain, for which the Canton Aargau has a particularly high responsibility for conservation. Additionally, 37 of the recorded species are character species for floodplains. Thus, the restoration can be considered very successful for ground beetles. Non-restored areas, characterized by river training measures, harbor generally half as many species at best. The number of species recorded per year varied between 68 and 82. Species turnover rate was between 28 and 45%. This reflects the change in habitats and hydrology over the five years. Open gravel/sand surfaces and annual ruderal habitats were reduced to one-third of their original area, while reed canary grass stands and perennial ruderal habitats tripled in size. On the other hand, the turnover is certainly also due to the low detection probability of rare species. Despite the strong decline in individual ground beetle species which typically occur on open gravel surfaces, it would be premature to initiate interventions to rebuild such areas. During the last year of the study, all typical gravel species observed in the previous years within the study area were found again. If anything, it would be more beneficial to build ponds with flat banks of fine sand within the forested sections of the floodplain or clear some patches to create more ruderal areas. RÉSUMÉ La zone alluviale de Rupperswil (canton d’Argovie) a été renaturée dans les années 2010-2011. De 2012 à 2016, les carabes ont été recensés annuellement. Au total, 116 espèces ont pu être identifiées. Parmi celles-ci, 12 espèces sont considérées comme en danger, potentiellement en danger ou rare selon la Liste Rouge. 37 espèces sont des espèces indicatrices pour les zones alluviales. Ainsi, la renaturation peut être considérée comme très réussie pour les carabes. Dans les surfaces non renaturées avec une dynamique alluviale réduite, causé par des mesures de construction fluviales, la moitié des espèces peuvent au mieux être trouvées. En comparaison de la Suisse dans son ensemble, la responsabilité de l’Argovie est très élevée pour le maintien en particulier de Bembidion atrocaeruleum, très fréquent, de B. prasinum et de Harpalus progrediens nombreux à Rupperswil. Pour un même effort d’échantillonnage, le nombre d’espèces trouvées a varié entre 68 et 82 pour les deux années. Le degré de turnover d’une année à l’autre s’est situé entre 28 et 45%. Ceci reflète d’une part le changement des biotopes et une hydrologie variable sur les cinq ans. Les alluvions sans végétation et les surfaces rudérales annuelles ont diminué d’environ un tiers alors que les Phalaridions et les surfaces rudérales pluriannuelles ont triplé. D’autre part, le turnover doit aussi être attribué à la probabilité réduite de trouver les espèces rares. Malgré un fort recul de certaines espèces particulières qui apparaissent typiquement dans les gravières ouvertes, il serait prématuré de créer de nouveau de telles surfaces par des interventions. Toutes les espèces de gravière ont encore pu être trouvées dans la région la dernière année d’étude. Le cas échéant, l’installation d’étangs dans la forêt de la zone alluviale avec des surfaces à sédiments fins provenant des berges de même qu’un nouvel écorchement de surfaces partielles pour la création de couloirs rudéraux seraient favorables. ZUSAMMENFASSUNG Die Aue Rupperswil (Kanton Aargau) wurde in den Jahren 2010-2011 renaturiert. Von 2012 bis 2016 wurden jährlich die Laufkäfer untersucht. Insgesamt konnten 116 Arten nachgewiesen werden. Davon sind 12 Arten gemäss Roter Liste gefährdet, potenziell gefährdet oder selten. 37 Arten sind Auenkennarten. Damit kann die Renaturierung bezüglich der Laufkäfer als sehr erfolgreich bezeichnet werden. In Gebieten, wo die Auendynamik durch flussbauliche Massnahmen stark reduziert ist, findet man bestenfalls halb so viele Arten. Im gesamtschweizerischen Vergleich ist die Verantwortung des Kanton Aargau für die Erhaltung insbesondere von Bembidion atrocaeruleum, in Rupperswil sehr häufig, B. prasinum, sowie Harpalus progrediens, beide zahlreich, sehr hoch. Die Anzahl der in den einzelnen Jahren bei gleichem Sammelaufwand gefundenen Arten variierte zwischen 68 und 82. Die Turnover-Rate der Arten in den Folgejahren betrug zwischen 28 und 45%. Dies widerspiegelt einerseits die Veränderung der Lebensräume sowie die unterschiedliche Hydrologie in den fünf Jahren. Offene Kies-Sandflächen und einjährige Ruderalfluren sind auf ca. einen Drittel geschrumpft während sich Rohrglanzgrasbestände und mehrjährige Ruderalfluren verdreifacht haben. Andererseits ist der Turnover sicher auch auf die geringe Auffindwahrscheinlichkeit selten vorkommender Arten zurückzuführen. Trotz starken Rückgängen einzelner Laufkäferarten, die typischerweise auf offenen Kiesflächen vorkommen, wäre es verfrüht, solche Flächen durch Eingriffe wieder zu schaffen. Es konnten auch im letzten Untersuchungsjahr noch alle typischen Kiesbank-Arten im Gebiet nachgewiesen werden. Allenfalls förderlich wären die Anlage von Tümpeln mit flachen aus Feinsedimenten bestehenden Uferpartien im Waldgebiet der Aue sowie das erneute Abschürfen einzelner Teilflächen zur Schaffung von Ruderalfluren