Nutrient Accumulation and Distribution in Cotton Promoted by Removal of Mulch Film

Plastic film mulching affects changes in nutrient contents in soil and absorption and utilization of nutrients in plants were by changing hydrothermal condition of soil.The temporal and spatial variation of the total soil salt and nutrient contents with mulch film removed at three different times during the early cotton growth stage and its effects on nutrient absorption and accumulation in cotton plants were studied over 2015-2017.The film removal treatments reduced salt accumulation in normal rainfall year(2017).Film removal increased contents of soil organic matter,the total phosphorus and available potassium at the end of growth stage,increased contents of soil hydrolyzable nitrogen and the total nitrogen in the surface soil layer(0-10 cm),and increased the total nitrogen contents in the deep soil layer(40-50 cm).Film removal increased accumulation of nitrogen and phosphorus nutrients in cotton plants in 2017 and accumulation of nitrogen,phosphorus and potassium nutrients in cotton plants in heavy rainfall year(2016).These experimental results indicated that removal of mulch film at an appropriate and targeted time in the bud stage of cotton promoted nutrient absorption.

Nutrient Accumulation Characteristics of Facility Soils with Different Planting Years in Lateritic Red Soil Region of Guangxi

[Objectives]To explore the nutrient accumulation characteristics of facility soil in different planting years in the lateritic red soil region of Guangxi.[Methods]The soil samples of facility cultivation and open field cultivation were collected in the lateritic red soil region of Guangxi,and the changes of soil pH,water-soluble salts,organic matter,available nutrients and total nutrients were analyzed.[Results]The acidification of the facility soil in the lateritic red soil region of Guangxi became more obvious with the extension of greenhouse planting years,the soil pH decreased by 0.34 units after continuous planting for 10 years,and the water-soluble content was more than 3 times that of the open field and it increased with the extension of the planting years.In addition,the degree of secondary salinization in facility soil became more serious,mainly moderate and mild salinization.The contents of soil organic matter,alkali-hydrolyzed nitrogen,available phosphorus,available potassium,total nitrogen and total phosphorus in the facility soil increased significantly,while total potassium did not change significantly.[Conclusions]This study is expected to provide a scientific basis for facility soil fertilization management,and to promote the sustainable and healthy development of facility cultivation industry.

Effect of slope position on leaf and fine root C,N and P stoichiometry and rhizosphere soil properties in Tectona grandis plantations

Little is known about C-N-P stoichiometries and content in teak(Tectona grandis)plantations in South China,which are mostly sited on hilly areas with lateritic soil,and the effect of slope position on the accumulation of these elements in trees and rhizosphere soils.Here we analyzed the C,N,P content and stoichiometry in leaves,fine roots and rhizosphere soils of trees on the upper and lower slopes of a 12-year-old teak plantation.The Kraft classification system of tree status was used to sample dominant,subdominant and mean trees at each slope position.The results showed that the C,N and P contents in leaves were higher than in fine roots and rhizosphere soils.The lowest C/N,C/P and N/P ratios were found in rhizosphere soils,and the C/N and C/P ratios in fine roots were higher than in leaves.Nutrient accumulation in leaves,fine roots and rhizosphere soils were significantly influenced by slope position and tree class with their interaction mainly showing a greater effect on rhizosphere soils.Leaf C content and C/N ratio,fine root C and P contents,and C/N and C/P ratios all increased distinctly with declining slope position.The contents of organic matter(SOM),ammonium(NH4+-N),nitrate-nitrogen(NO3--N)and available potassium(AK)in rhizosphere soils were mainly enriched on upper slopes,but exchange calcium(ECa),available phosphorus(AP),and pH were relatively lower.Variations in the C,N and P stoichiometries in trees were mainly attributed to the differences in rhizosphere soil properties.N and P contents showed significant positive linear relationships between leaf and rhizosphere soil,and C content negative linear correlation among leaves,fine roots and rhizosphere soils.Chemical properties of rhizosphere soils,particularly C/N and NH4+-N,had significant effects on the leaf nutrients in trees on the upper slope.Correspondingly,rhizosphere soil properties mainly influenced fine root nutrients on the lower slope,and soil AK was the major influencing factor.Overall,these results offer new insights for the sustainability and management of teak plantations in hilly areas.

Pelagic-benthic coupling of the microbial food web modifies nutrient cycles along a cascade-dammed river

Cascade dams disrupt the river continuum,altering hydrology,biodiversity and nutrient flux.Describing the diversity of multi-trophic microbiota and assessing microbial contributions to the ecosystem processes are prerequisites for the restoration of these aquatic systems.This study investigated the microbial food web structure along a cascade-dammed river,paying special attention to the multi-trophic relationships and the potential role of pelagic-benthic coupling in nutrient cycles.Our results revealed the discontinuity in bacterial and eukaryotic community composition,functional group proportion,as well as a-diversity due to fragmentation by damming.The high microbial dissimilarity along the river,with the total multi-trophic P-diversity was 0.84,was almost completely caused by species replacement.Synchronization among trophic levels suggests potential interactions of the pelagic and the benthic groups,of which the p-diversities were primarily influenced by geographic and environmental factors,respectively.Dam-induced environmental variations,especially hydrological and nutrient variables,potentially influence the microbial food web via both top-down and bottom-up forces.We proposed that the cycles of carbon,nitrogen and phosphorus are influenced by multi-trophic groups through autotrophic and heterotrophic processes,predator-prey relationships,as well as the release of nutrients mainly by microfauna.Our results advance the notion that pelagic-benthic trophic coupling may intensify the accumulation of organic carbon,ammonium and inorganic phosphorus,thereby changing the biogeochemical patterns along river systems.As a consequence,researchers should pay more attention to the multi-trophic studies when assessing the environmental impacts,and to provide the necessary guidance for the ecological conservation and restoration of the dam-regulated systems.

Effect of fertilization patterns on the assemblage of weed communities in an upland winter wheat field

Aims Understanding the response of farmland weed community assembly to fertilization is important for designing better nutrient management strategies in integrated farmland ecological systems.Many studies have focused on weed characteristics,mainly crop–weed competition responses to fertilization or weed communities alone.However,weed community assembly in association with crop growth is poorly understood in the agroecosystems,but is important for the determination of integrated weed management.Biodiversity promotes ecosystem productivity in the grassland,but whether it applies to the agroecosystems is unclear.Based on an 11-year field experiment,the cumulative effects of different fertilization patterns on the floristic composition and species diversity of farmland weed communities along with wheat growth in a winter wheat–soybean rotation were investigated.Methods The field trial included five fertilization patterns with different combinations of N,P and K fertilizers.Species composition and diversity of weed communities,aboveground plant biomass and nutrient accumulation of weeds and winter wheat,light penetration to the ground surface and wheat yield were measured at each plot in 2009 and 2010.Multivariate analysis,regression and analysis of variance were used to analyze the responses of these parameters to the different fertilization treatments.Important Findings Four dominant weeds(Galium aparine L.,Veronica persica Poir.,Vicia sativa L.and Geranium carolinianum L.)accounted for~90%of the total weed density in the 2 years of experimental duration.The residual weed community assembly was influenced primarily by topsoil available nutrients in the order P>N>K.Competition for nutrients and solar radiation between crops and weeds was the main indirect effect of fertilization on the changes in weed community composition and species diversity.The indices of species diversity(species richness,Shannon–Wiener,Pielou and Simpson indices)showed significant linear relationships with wheat yield.The balanced fertilization treatment was more efficient at inhibiting the potential growth of weeds because of solar radiation being intercepted by wheat.These results support the conclusion that wheat yield is favored by balanced fertilization,whereas the weed community is favored by PK fertilization in terms of density and diversity.However,the negative effects on wheat yield may be compromised by simultaneous positive effects of weed communities in the fertilization treatments,for instance,the NP and NK treatments,which are intermediate in terms of increasing wheat production and to a level maintaining a diverse community.