Biochar applied with appropriate rates can reduce N leaching, keep N retention and not increase NH 3 volatilization in a coastal saline soil

https://escholarship.org/content/qt7001s8mq/qt7001s8mq.pdf?t=ojx5jo

Impacts of land use and population density on seasonal surface water quality using a modified geographically weighted regression

Biochar applied at an appropriate rate can avoid increasing NH3 volatilization dramatically in rice paddy soil.

Rice production, nitrous oxide emission and ammonia volatilization as impacted by the nitrification inhibitor 2-chloro-6-(trichloromethyl)-pyridine

/pdf/do-high-nitrogen-use-efficiency-rice-cultivars-reduce-2g8spl6wh5.pdf

Do high nitrogen use efficiency rice cultivars reduce nitrogen losses from paddy fields

Sewage effluents are increasingly used for farmland irrigation worldwide. This practice makes N losses via gaseous forms and leaching process more complex. Twelve repacked lysimeters with 90 cm height and 25 cm inner diameter were used for comprehensively determining am- monia (NH3) and nitrousoxide(N2O) emissionsand N leachinglossesina rice-wheat cropping system irrigated with N-rich wastewater from a live- stock pond. There were four irrigation treatments with three replications: wastewater with high N concentration (HW), wastewater with medium N concentration (MW, one-half dilution of wastewater of HW), wastewater with low N concentration (LW, one-fourth dilution of wastewater of HW), and ultrapure water control (CK). All treatments received equal amounts of total N (225 kg N ha �1 in the riceseasonand 150kgNha �1 in thewheat season) by balancing with commercial N fertilizer. The wastewater was provento be as effective ascommercialN fertilizer to achieve the optimum crop yields when applied in an appropriate amount. The NH3 emission, N leaching, and N2O emission losses accounted for 16.2 to 19.8%, 4.6 to 6.4%, and 0.26 to 0.35% of the total N applied in the rice season, respec- tively, whereas they were 2.7 to 3.3%, 2.2 to 2.8%, and 0.77 to 1.0% in the wheat season. Irrigating with wastewater did not change the NH3 emission flux pattern after N fertilizer (urea) was applied, but it boosted the NH3 emission flux to a certain extent in the rice season, especially for the MW treatment, which was mainly attributed to the high ammonium con- tent and pH of the flood surface water resulting from a combined effect of wastewater and urea-N application. In addition, N-rich wastewater irri- gation did not significantly increase N2O emission and N leaching when the total N inputs and the amount of irrigation were the same.

Laboratory Lysimeter Analysis of NH3 and N2O Emissions and Leaching Losses of Nitrogen in a Rice-Wheat Rotation System Irrigated With Nitrogen-Rich Wastewater

Constructed wetlands (CWs) have been used effectively to remove nitrogen (N) and phosphorus (P) from non-point sources. Effluents of some CWs were, however, still with high N and P concentrations and remained to be pollution sources. Widely distributed paddy fields can be exploited to alleviate this concern. We were the first to investigate a combination system of three-level CWs with wetland paddy fields in a full scale to remove N and P from rural unregulated non-point sources. The removal efficiencies (REs) of CWs reached 57.3 % (37.4–75.1 %) for N and 76.3 % (62.0–98.4 %) for P. The CWs retained about 1,278 kg N ha−1 year−1 and 121 kg P ha−1 year−1. There was a notable seasonal change in REs of N and P, and the REs were different in different processing components of CWs. The removal rates of wetland paddy fields adopt “zero-drainage” water management according to local rainfall forecast and physiological water demand of crop growth reached 93.2 kg N ha−1 year−1 and 5.4 kg P ha−1 year−1. The rice season had higher potential in removing N and P than that in the wheat season. The whole combined system (0.56 ha CWs and 5.5 ha wetland paddy fields) removed 1,790 kg N year−1 and 151 kg P year−1, which were higher than those from CWs functioned alone. However, another 4.7-ha paddy fields were needed to fully remove the N and P in the effluents of CWs. The combination of CWs and paddy fields proved to be a more efficient nutrient removal system.

Combination system of full-scale constructed wetlands and wetland paddy fields to remove nitrogen and phosphorus from rural unregulated non-point sources.

Peikun Jiang

Papers

Laboratory Lysimeter Analysis of NH3 and N2O Emissions and Leaching Losses of Nitrogen in a Rice-Wheat Rotation System Irrigated With Nitrogen-Rich Wastewater

Combination system of full-scale constructed wetlands and wetland paddy fields to remove nitrogen and phosphorus from rural unregulated non-point sources.