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Improving poor physical structural components has been gaining increasing recognition for its role in enhancing soil fertility. This study was conducted to identify the key physical structural barriers for soil fertility and their effects on crop productivity in Aquic Inceptisol. Based on the strip sampling in Fengqiu County, arable soils from 0–0.40 m profile pits were collected to determine the physical structural components including plough layer thickness, textural composition, soil aggregation and bulk density, as well as stocks of soil organic matter (SOM), total nitrogen (TN) and total phosphorus (TP). The grain yields of wheat and maize and amounts of fertilizer applications were also investigated. The tested soil was dominated by a plough layer of 0.15–0.18 m and sandy loam texture, which constituted 50% and 59%, respectively, of the studied profile pits. Compared to the soil with

The backward Lagrangian stochastic (BLS) model and open-path tunable diode laser (OPTDL) analyzer were used to monitor ammonia (NH3) emissions from urea applied to winter wheat in the North China Plain. The high-temporal resolution measurements of ammonia concentrations provided an opportunity for estimating the diel patterns of ammonia emissions, as well as valuable information about the factors that influence NH3 emissions. The results showed both large diel variability and daily variability in NH3 volatilization, with NH3 emissions highest during the daytime. The diel pattern of ammonia volatilization depended mainly on the diel variation of wind speed and soil temperature, while the overall pattern of NH3 loss was strongly affected by soil moisture content, soil NH4 +-N concentration, wind speed and soil temperature. At the end of the measurement period, the cumulative NH3 loss was 12.21–16.43 kg N ha−1, calculated based on different time scale average Q BLS. Due to sensitivity of the OPTDL analyzer, the estimated total ammonia loss was still doubtful in this study.

A viable method—open-path tunable diode laser absorption spectroscopy (OPTDL) in conjunction with a backward Lagrangian stochastic (bLS) dispersion model—has been used for micrometeorological monitoring of ammonia fluxes. In this technique, the gas concentration measured with the OPTDL sensor is used to infer the surface emission rate with the aid of dispersion model calculations. On the basis of numerous assessment experiments and field trials, several beneficial strategies for using the OPTDL technique properly to monitor atmospheric NH3 concentrations in the field have been summarized. Theoretically, the location of the concentration measurement can be anywhere in the emission plume, but in practice, the concentration measurement position must be carefully selected to avoid making measurements which are on the periphery of the downwind plume or are affected by obstructions. To obtain accurate estimates, periods with low friction velocity or extreme atmospheric stability, where Monin–Obukhov similarity theory-based relationships are invalid, or unrepresentative estimates due to unsuitable wind direction, should be excluded. A validation experiment showed that there was no significant difference between the ammonia emission rates obtained by the micrometeorological mass balance method and those obtained by the bLS model combined with the OPTDL technique. This study also indicated the potential of the bLS and OPTDL technique for investigation of diurnal emission patterns and environmental influences.