Leaching of Nutrient Elements in a Red Soil Derived from Quaternary Red Clay

A red soil derived from Quaternary red clay was employed to study nutrient leaching with soil columns repacked in laboratory. The objective was to identify the effects of fertilization practices on leaching patterns and magnitudes of Ca2+, Mg2+, K+, NH+, and NO-. The treatments were CK (as a control), CaCO3,CaSO4, MgCO3, Ca(H2PO4)2, urea, KCI, and multiple (a mixture of the above-mentioned fertilizers). The fertilizers were added to the bare surface of the soil columns, and then the columns were leached with 120 mL deionized water daily through peristaltic pumps over a period of 92 days. Leaching processes of NH+, and NO- were only measured in CK, urea, and multiple treatments which were directly related to N leaching.Results showed that sole application of CaSO4, and Ca(H2PO4)2 scarcely had any effect on the leaching losses of Ca2+, Mg2+, and K+; the application of MgCO3 stimulated the leaching of Mg2+; the application of CaCOs promoted the leaching of Ca2+, Mg2+ and K+; urea treatment also promoted the leaching of K+ and NH+, and NO- leaching mainly occurred at late stage of leaching process in particular; under KCI treatment, leaching of Ca2+, Mg2+, and K+ was promoted to a large extent; under multiple treatment,leaching of Ca2+, Mg2+, K+, NH+, and NO- was all increased and NO- was mainly leached at the end of leaching process and still had a trend of increase.

Sugarcane bagasse amendment mitigates nutrient leaching from a mineral soil under tropical conditions

Large quantities of organic by-products are generated by the sugarcane industry during sugar extraction process.These by-products may be used as soil amendments to improve soil quality,as nutrient leaching is common in mineral soils of Florida in USA due to their sandy texture and frequent rain events.A soil column study was designed to evaluate the effects of bagasse application at 85 t ha^(-1) of fresh bagasse,170 t ha^(-1) of fresh bagasse,and 170 t ha^(-1) of fresh bagasse+nitrogen(N)on the leaching potential of carbon(C),N,phosphorus(P),and potassium(K).Bagasse was incorporated within the topsoil(0-15 cm)in outdoor soil columns exposed to natural conditions,with periodical irrigation during the experiment.After approximately 57 weeks,the distributions of C,N,P,and K were evaluated at three soil depths(i.e.,0-15,15-30,and 30-53 cm)within the soil columns.Total organic C(TOC),N,and P in leachates decreased significantly from the soils amended with bagasse compared with the control with no bagasse and no N.Based on K content changes in the columns,bagasse could also be utilized as a potential source of K for plants.Overall,application of bagasse as a soil amendment might be an effective way to sustainably reutilize organic by-products while reducing concerns regarding major nutrients entering groundwater resources.The results of this study could assist in developing nutrient management plans of using sugarcane bagasse as a potential soil amendment in mineral soils.

Evaluation of Spatial and Vertical Variability of Nitrogen and Phosphorus in Sewage-Irrigated Soil in Tongliao, China

The reuse of wastewater for the irrigation of farmlands is gaining popularity, and the nutrient leaching associated with wastewater irrigation is becoming a matter of concern. The variability of nitrogen and phosphorus frac- tions in wastewater-irrigated soil was investigated in both horizontal and vertical directions in Kongjiaxiang, Tongliao, Inner Mongolia, China. The results showed that wastewater irrigation resulted in the concentrations of available N and P being 40.36% and 66.49% higher, respectively, than those with groundwater irrigation. Different forms of N and P exhibited significantly different distribution pattems. Higher concentrations of NO~ and total available N, as well as of those of Ca-P and total available P were observed near wastewater irrigation channels. Ca-P has a spatial distribu- tion pattern similar to that of available P. The concentrations of NO3 and NH4 were the highest in top soil and de- creased with depth. The complex interactions between nitrate leaching and nitrogen transformation processes （e.g., nitrification, denitrification, and mineralization） determined the vertical profile of NO3. The significant amount of NH~ loss inhibited its deep seepage. The Ca-bound compound contained more P than other inorganic fractions as a result of high Ca levels throughout the soil profile. The differences in the concentrations of Ca-bound P at different depths could be due to the upward flux or translocation of Ca from subsurface to surface soil and the sequestration of P.

Anaerobically Digested Dairy Fiber in Soilless Potting Media for Herbaceous Perennials

Sphagnum peat moss has been a primary component of soilless potting media for decades;however, concerns over the sustainability of harvesting peat have fostered a search for renewable media components. Anaerobically digested dairy fiber (ADDF), a by-product of methane production, shows promise as an alternative to peat. Herbaceous nursery crops including “Jack Frost” brunnera (Brunnera macrophylla I.M. Johnst), “Moonbeam” coreopsis (Coreopsis verticillata L.), “Whoops-a-Daisy” Shasta daisy (Leucanthemum × superbum Bergmans ex J.W. Ingram), “Kobold Original” liatris (Liatris spicata (L.) Willd.) and “David” phlox (Phlox paniculata L.) were grown in media containing bark-peat-perlite or bark-ADDF-perlite in a 4:2:1 proportion. All leachate was collected from pots to evaluate cumulative nitrogen and phosphate leaching. Brunnera grew to a similar size and quality in both mixes, although brunnera in the bark-ADDF-perlite mix had slightly chlorotic leaf margins. Coreopsis grew to a similar size and quality in both mixes but was slightly etiolated and chlorotic in bark-ADDF-perlite. Shasta daisy grown in bark-ADDF-perlite were larger than those grown in bark-peat-perlite. Both mixes produced similar growth and quality liatris and phlox. More ammonium, nitrate and phosphate were recovered from leachate from bark-ADDF-perlite than from bark-ADDF-perlite.

The potential for biochar application in rubber plantations in Xishuangbanna,Southwest China:a pot trial

Biochar can enhance crop production and sequester carbon,but there have been few studies with tree crops.Rubber plantations cover more than 8 million hectares in Southeast Asia,so we assessed the feasibility of biochar application in these plantations with a pot trial.Rubber seedlings were planted in soil with four concentrations(0,1.25%,2.5% and 5%,w/w)of biochar combined with two concentrations of compound fertilizer(0 kg/ha and 300 kg/ha).Soil properties and seedling growth were measured,and a leaching experiment was conducted in the rainy season.Our results show that biochar increased pH,water content(27.4-65.1%),total carbon(25.4-53.6%),nitrate nitrogen,and available phosphorus in the soil,and decreased bulk density(3.2-23.9%).Biochar treatment reduced leaching of ammonium nitrogen and ortho-P.Biochar increased seedling nutrient uptake(C,N,P and K),with 2.5% and 5% biochar showing the largest effects,but seedling biomass was the highest with 1.25%,and declined in 2.5% and 5%.Our results suggest that biochar addition is an effective way to improve rubber plantation soils,sequester more carbon and decrease nutrient leaching,but the optimum application rate under field conditions needs further research.