8 research outputs found
Phosphorus Release from Unamended and Gypsum- or Biochar-Amended Soils under Simulated Snowmelt and Summer Flooding Conditions
No full textProlonged flooding changes the oxidation–reduction status of soils, often enhancing P release to overlying floodwater. We studied P release from unamended, gypsum-amended, and biochar-amended soils under simulated snowmelt flooding (previously frozen, cold flooding at +4°C) and summer flooding (unfrozen, warm flooding at +22°C) using two soils, Fyala clay (FYL-Cl) and Neuenberg sandy loam (NBG-SL), from Manitoba, Canada. Amended and unamended soils were packed into vessels and flooded under cold and warm temperatures in the laboratory. Pore water and floodwater samples were taken weekly for 6 wk after flooding (WAF) and thereafter biweekly for 10 WAF and analyzed for dissolved reactive P (DRP), pH, and cation concentrations. The NBG-SL showed a significantly higher DRP concentration in pore water and floodwater despite its low Olsen P content. Redox potential (Eh) decreased slowly under cold versus warm flooding; hence, redox-induced P release was substantially lower under cold flooding. Gypsum amendment significantly decreased the floodwater DRP concentrations in NBG-SL by 38 and 35% under cold and warm flooding, respectively, but had no significant effect in FYL-Cl, which had low DRP concentrations (<1.2 mg L−1) throughout the flooding period. Biochar amendment significantly increased floodwater DRP concentrations by 27 to 68% in FYL-Cl under cold and warm flooding, respectively, but had no significant effect in NBG-SL. The results indicate substantially less P release under cold than under warm flooding. Gypsum was effective in reducing floodwater DRP concentrations only at high DRP concentrations; thus, the effectiveness was greater under warm than under cold flooding conditions."Funding for this research was provided by a National Sciences and Engineering Research Council (NSERC) Discovery Grant and a University of Winnipeg Major Grant to Darshani Kumaragamage, and a fellowship awarded by the University of Winnipeg–Queen Elizabeth Advanced Scholar Program to R.S. Dharmakeerthi."https://acsess.onlinelibrary.wiley.com/doi/10.2134/jeq2019.02.009
Exploring the Response of Paddy for Varying Levels of Soil Phosphorus in Tropical Soilscapes
No full textBetter management of soil Phosphorus (P) in crop cultivation leads to environmental and economic benefits. Proper understanding of the crop response to inherent soil P is important to develop site-specific recommendations. The objective of this study was to assess the yield response of paddy for varying levels of inherent available soil P in Alfisols and Ultisols. Surface soil (0-15 cm depth) P content was measured in 71 paddy fields in three districts of Sri Lanka, namely Anuradapura, Kurunegala and Polonnaruwa. Experiment plots (3x6 m) at each site comprised of ample application of N, P and K and an omission treatment plot of P. Total yield of each plot was recorded at the end of the season. The available P showed a large variability (range=from 2.7 ppm to 34.2 ppm, CV=78%) meanwhile 31% of the experimental sites were below the optimum soil P level for paddy (5 ppm).Omission plot treatments did not show a clear yield response for added P. Very low correlation coefficient between the yield of the omission treatment with the inherent P level (0.05), indicated that inherent P level will not determine the yield. The yield response was plotted against the Olsen P, and very low R2 value (0.03) indicated the Olsen P content does not clearly reflect the actual P requirement in every experimental sites. Short term availability of P from soil reserves cause to mask the effects of spatial variability on yield response and it was concluded that further studies are required to assess P dynamics to take SSNM decisions.Keywords: Paddy, Phosphorus, Site specific nutrient managemen
Gypsum Amendment Reduces Redox-Induced Phosphorous Release from Freshly Manured, Flooded Soils to Floodwater
No full textThe effectiveness of gypsum in reducing runoff P losses from soils and the mechanisms responsible are well documented; however, gypsum amendment effects in reducing redox-induced P losses from flooded soils are less researched and documented. We examined the effect of gypsum amendment on P release from freshly manured soils to pore water and floodwater with continuous flooding for 56 d in the laboratory. Three soils (Pembina, Denham, and Dencross series) collected from Manitoba, Canada, were preincubated with liquid swine manure. Each preincubated manured soil was packed into vessels with or without recycled wallboard gypsum in triplicates and flooded for 56 d, during which pore water and floodwater were sampled weekly and analyzed for pH and dissolved reactive P (DRP), Ca, Mg, Fe, and Mn concentrations. Change in soil redox potential (Eh) with flooding was also monitored. Wallboard gypsum amendment significantly decreased the pore water and surface floodwater DRP concentrations in all three soils for most days after flooding (DAF). The Dencross soil, which had Olsen P about fivefold greater than the other soils, showed the greatest magnitude decrease in DRP concentration with gypsum amendment, by 1.27 mg L−1 on 49 DAF and 0.99 mg L−1 on 21 DAF for pore water and floodwater, respectively. Gypsum amendment (i) delayed the Eh reduction with flooding beyond +200 mV, (ii) decreased pore water pH, and (iii) increased concentrations of Ca, Mg, and Mn in pore water favoring precipitation of P, all of which may have directly or indirectly reduced the P release from flooded soils to overlying floodwater.Funding for this research was provided by the University of Winnipeg Major Grant and a Natural Sciences and Engineering Research Council Discovery Grant to Darshani Kumaragamage, and a fellowship awarded by the Queen Elizabeth Advanced Scholar Program to R.S. Dharmakeerthi.https://acsess.onlinelibrary.wiley.com/doi/10.2134/jeq2018.08.030
Phosphate Solubilizing Bacteria and Fungi Isolated from Rubber (Hevea brasiliensis) Root Rhizosphere, Their Biofilm Formation and Phosphate Solubilizing Abilities
No full textThe ability of some soil microorganisms and their biofilm combinations to convert insolubleforms of phosphorus to an accessible form is an important trait associated with plant Pnutrition. The phosphorus solubilizing potential of bacteria and fungi isolated from Hevearhizosphere and their effective biofilm communities were evaluated using solid and liquidmedia under in vitro conditions. Phosphate solubilization ability of them were tested oncalcium phosphate media by analysing the soluble P content after incubation at 28±2°C. Outof the microbial isolates, 10 bacterial colonies and one fungal colony formed haloes (clearzones) around the isolate growing on solid media containing calcium phosphate as the solephosphate source. Spectrophotometric quantification of phosphorus solubilization in theliquid media showed that the ten bacterial isolates, and ten fungal isolates solubilizedinsoluble calcium phosphate in to the liquid media in the range of 200 – 450 and 200 – 300mg P L-1 respectively. Biofilm showed significantly higher P solubilization (853.3±25.17 mgP L-1) than their bacteria and fungi counterparts alone. Phosphate solubilization of bacteria,fungi and their biofilm could be attributed to the secretion of organic acids. A significant dropin the pH of the broth media (4.7 to 5.6) compared to the pH of the control treatment (6.8-7.0)was observed. pH change in the media could be due to secretion of organic acids bymicroorganisms and/or utilisation of compounds in the broth media. Although there was asignificant synergistic effect on P solubilization due to biofilm formation, pH in the liquidmedia of their mono cultures and biofilm were not significantly different. This observationwarrants further investigation
Evaluating the nitrification inhibition potential of selected botanicals and their non-target effects
No full textNitrification inhibitors (NI) are aimed at improving N-fertilizer use efficiency in cropping systems. This study aimed to assess the nitrification inhibition potential and non-target effects of dry leaf powders (botanicals) of ten plant species [neem (Azadirachta indica), lantana (Lantana camara), karanda (Pongamia pinnata), Brachiaria humidicola, cinnamon (Cinnamomum verum), clove (Syzygium aromaticum), wild-sunflower (Tithonia diversifolia), mee (Madhuca longifolia), nutmeg (Myristica fragrans) and pepper (Piper nigram)]. The effect of botanicals on the growth of three ammonia oxidizing bacteria isolates (M4, M5 and M7) and NO3The presentation of the authors' names and (or) special characters in the title of the pdf file of the accepted manuscript may differ slightly from what is displayed on the item page. The information in the pdf file of the accepted manuscript reflects the original submission by the author
A laboratory assay of in-situ stabilization of toxic metals in contaminated boreal forest soil using organic and inorganic amendments
No full textMetal-contaminated soils present a great threat to natural ecosystems and human health. Remediation studies focusing on metal-polluted soils with high organic matter (OM > 20%) are limited. This study evaluated the effectiveness of biochar, compost, diammonium phosphate (DAP), and iron oxides (Fe-O), in immobilizing metals from an OM-rich boreal forest soil contaminated with arsenic (As), cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn). A laboratory incubation study was conducted with soil amended with biochar (5% w w−1), compost (5% w w−1), DAP (0.2% w w−1), or Fe-O (0.2% w w−1), and a control (without amendment) for 6 months at field capacity moisture content. Metal concentrations were determined in pore water collected at 0, 2, 4, and 6 months after incubation. Soil was extracted sequentially for metals after the incubation period. Metal concentrations in pore water were significantly reduced by different amendments as follows: As by biochar and Fe-O, Cd by biochar, compost, and DAP, Cu by biochar, Pb by compost and DAP, and Zn by biochar and compost. Sequential extractions revealed biochar and (or) compost transferred Cd, Cu, Pb, and Zn from the labile pool to the non-labile pool confirming their effectiveness as amendments for remediation of metal-contaminated OM-rich boreal forest soil.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author
Partial Factor Productivity, Agronomic Efficiency, and Economic Analyses of Maize in Wheat-Maize Cropping System in Pakistan
No full textGetting maximum benefits from cereals do not lie in reducing N-rate and its number of splits but lowering cost per unit cereal production through higher yields. Field experiments were conducted on maize (Zea mays L.) at the New Developmental research Farm of NWFP (Northwest Frontier Province) Agricultural University Peshawar-Pakistan during 2002-03 and 2003-04 in order to investigate effects of variable rates of N and its time of application on the partial factor productivity (PFPN), agronomic efficiency (AEN), net returns (NR), value-cost ratio (VCR) and marginal returns (MR). The 2 x 3 x 6 factorial experiment was designed having two plant densities (D1 = 60,000 and D2 = 100,000 plants ha-1) and three N levels (N1 = 60, N2 = 120 and N3 = 180 kg N ha-1) applied to main plots, while six split application of N in different proportions were applied to subplots in two equal (T1), three equal (T2), three unequal (T3), four equal (T4), five equal (T5) and five unequal splits (T6) at sowing and with 1st, 2nd, 3rd and 4th irrigation at two wk intervals. Maize ranked first with maximum PFPN, AEN, NR, VCR and MR at higher than at lower plant density, and the increase in all these parameters studied in the experiments was more in 2003-04 as compared to 2002-03. Both PFPN and AEN showed negative relationship with increase in N rates and the cast that vary, but NR, VCR and MR showed positive relationship with increase in N rates and the cost that vary. Among time of N application, maximum PFPN, AEN, NR, VCR and MR were calculated when N was applied in five equal splits (T5) almost comparable with T4 and T6 but was more economical when compared with T1, T2, and T3. In conclusion, the findings suggest that growing maize at D2 applied with N3 in four to five splits is more economical in the wheat-maize cropping system of NWFP.maize, Zea mays L., planting density, nitrogen, agronomic efficiency, economics, Crop Production/Industries, Farm Management, International Development, Production Economics, Productivity Analysis,
