Biochar with near-neutral pH reduces ammonia volatilization and improves plant growth in a soil-plant system: A closed chamber experiment.

Ammonia (NH3) volatilization is considered as one of the major mechanisms responsible for the loss of nitrogen (N) from soil-plant systems worldwide. This study investigated the effect of biochar amendment to a calcareous soil (pH 7.8) on NH3 volatilization and plant N uptake. In particular, the effect of biochar's feedstock and application rate on both NH3 volatilization and plant growth were quantified using a specially designed closed chamber system. Two well-characterized biochars prepared from poultry manure (PM-BC) and green waste compost (GW-BC) were applied to the soil (0, 0.5, 1, 1.5 and 2% w/w equivalent to 0, 7.5, 15, 22 and 30 t ha-1) and wheat (Triticum aestivum, variety: Calingiri) was grown for 30 days. Both PM-BC and GW-BC decreased NH3 volatilization to a similar degree (by 47 and 38%, respectively), in the soil-plant system compared to the unamended control. Higher plant biomass production of up to 70% was obtained in the closed chamber systems with the addition of biochar. The increase in plant biomass was due to the reduction in N loss as NH3 gas, thereby increasing the N supply to the plants. Plant N uptake was improved by as much as 58% with biochar addition when additional NPK nutrients were supplied to the soil. This study demonstrates that the application of biochars can mitigate NH3 emission from calcareous agricultural cropping soil and that the retained N is plant-available and can improve wheat biomass yield.

Mandal S ，Donner E ，Smith E ，Sarkar B ，Lombi E ... -  《-》

Biochar-induced concomitant decrease in ammonia volatilization and increase in nitrogen use efficiency by wheat.

Ammonia (NH3) volatilization is a major nitrogen (N) loss from the soil, especially under tropical conditions, NH3 volatilization results in low N use efficiency by crops. Incubation experiments were conducted using five soils (pH 5.5-9.0), three N sources such as, urea, di-ammonium phosphate (DAP), and poultry manure (PM) and two biochars such as, poultry litter biochar (PL-BC) and macadamia nut shell biochar (MS-BC). Ammonia volatilization was higher at soil with higher pH (pH exceeding 8) due to the increased hydroxyl ions. Among the N sources, urea recorded the highest NH3 volatilization (151.6 mg kg(-1)soil) followed by PM (124.2 mg kg(-1)soil) and DAP (99 mg kg(-1)soil). Ammonia volatilization was reduced by approximately 70% with PL-BC and MS-BC. The decreased NH3 volatilization with biochars is attributed to multiple mechanisms such as NH3 adsorption/immobilization, and nitrification. Moreover, biochar increased wheat dry weight and N uptake as high as by 24.24% and 76.11%, respectively. This study unravels the immense potential of biochar in decreasing N volatilization from soils and simultaneously improving use efficiency by wheat.

Mandal S ，Thangarajan R ，Bolan NS ，Sarkar B ，Khan N ，Ok YS ，Naidu R ... -  《-》

Ameliorating Effects of Biochar Derived from Poultry Manure and White Clover Residues on Soil Nutrient Status and Plant growth Promotion--Greenhouse Experiments.

Abbasi MK ，Anwar AA 《PLoS One》

Floating duckweed mitigated ammonia volatilization and increased grain yield and nitrogen use efficiency of rice in biochar amended paddy soils.

Biochar (BC) potentially accelerates ammonia (NH3) volatilization from rice paddy soils. In this regard, however, application the floating duckweed (FDW) to biochar-amended soil to control the NH3 volatilization is not studied up-to-date. Therefore, the impacts of BC application with and without FDW on the NH3 and nitrous oxide (N2O) emissions, NUE and rice grain yield were evaluated in a soil columns experiment. We repacked soil columns with Hydragric Anthrosol and Haplic Acrisol treated in triplicates with Urea, Urea + BC and Urea + BC + FDW. Total NH3 losses from Hydragric Anthrosol and Haplic Acrisol were 15.2-33.2 kg N ha-1 and 19.6-39.7 kg N ha-1, respectively. Urea + BC treatment recorded 25.6-43.7% higher (p < 0.05) NH3 losses than Urea treatment, attributing to higher pH value of floodwater. Floating duckweed decreased soil pH and therefore significantly reduced (p < 0.05) the NH3 volatilizations from the two soils by 50.6-54.2% over Urea + BC and by 34.2-38.0% over Urea treatment. Total N2O emissions from Hydragric Anthrosol and Haplic Acrisol were 1.19-3.42 kg N ha-1 and 0.67-2.08 kg N ha-1, respectively. Urea + BC treatment increased N2O emissions by 58.8-68.7% and Urea + BC + FDW treatment further increased N2O emission by 187.4-210.4% over Urea treatment. Higher ammonium content of the topsoil, explained the N2O increases in the Urea + BC and Urea + BC + FDW treatments. Urea + BC slightly reduced the rice grain yield and NUE, while the Urea + BC + FDW promoted both rice yield and NUE. Our data indicate that co-application of FDW along with BC in paddy soil could mitigate the NH3 volatilization and enhance the rice grain yield and NUE.

Sun H ，A D ，Feng Y ，Vithanage M ，Mandal S ，Shaheen SM ，Rinklebe J ，Shi W ，Wang H ... -  《-》

Biological nitrification inhibitor co-application with urease inhibitor or biochar yield different synergistic interaction effects on NH(3) volatilization, N leaching, and N use efficiency in a calcareous soil under rice cropping.

Nitrogen management measures (NMMs) such as the application of urease inhibitors (UIs), synthetic nitrification inhibitors (SNIs), and biochar (BC) are commonly used in mitigating nitrogen (N) loss and increasing fertilizer recovery efficiency (FRE) in agriculture. Calcareous soil under rice cropping is characterized by high nitrification potential, N loss risk, and low FRE. Application of SNIs may stimulate NH3 volatilization in high pH soils and the effects of SNIs on FRE are not always positive. BNIs have many advantages over SNIs. Whether combined application of BNI, UI, and BC that can result in a synergistic effect of improving FRE and decreasing N loss in a calcareous soil under rice cropping worth investigating. In this study, we conducted pot experiments to investigate the effects of single and co-application of BNI (methyl 3-(4-hydroxyphenyl) propionate or MHPP, 500 mg kg-1 soil), UI (N-(n-butyl), thiophosphoric triamide or NBPT, 2% of urea-N), or BC (wheat straw, 0.5% (w/w)) with chemical fertilizer on NH3 volatilization, N2O emission, N leaching, crop N uptake, and FRE in a calcareous soil under rice cropping. Our results demonstrated that those NMMs could mitigate NH3 volatilization by 12.5%-26.5%, N2O emission by 62.7%-73.5%, and N leaching loss by 17.5%-49.0%. However, BNI might have a risk of increasing NH3 (5.98%) volatilization loss. Among those NMMs, double inhibitors (BNI plus UI) yielded a synergistic effect that could mitigate N loss to the maximum extent and effectively improve FRE by 25.4%. The mechanisms of the above effects could be partly ascribed to the niche differentiation between the abundance of AOA and AOB and the changed community structure of AOB, which could further influence nitrification and N fate. Our results demonstrated that co-application of BNI and UI with urea is an effective strategy in reducing N loss and improving FRE in a calcareous soil under rice cropping.

Lan T ，Huang Y ，Song X ，Deng O ，Zhou W ，Luo L ，Tang X ，Zeng J ，Chen G ，Gao X ... -  《-》