[Factors influencing ammonia volatilization in a winter wheat field with plastic film mulched ridges and unmulched furrows].

The objective of this experiment was to quantify ammonia volatilization from a winter wheat field with plastic film mulched-ridges and unmulched-furrows (PMRF). The trial was conducted during the 2010-2011 winter wheat growing season at Yangling, Shaanxi Province. Ammonia volatilization from the soil was measured using the closed-chamber method. The results indicated that NH3 emission losses ranged between (1.66 +/- 0.3) and (3.28 +/- 0.51) kg x hm(-2) in the PMRF treatment. In comparison, the NH3 emission loss was (4.68 +/- 0.35) kg x ha(-1) in the conventional tillage treatment (i. e., smooth soil surface). The PMRF treatment reduced NH3 emissions by 29.8 to 63.8% compared with the conventional treatment. The NH3 emission losses were equivalent to 1.9% of the applied N in the conventional practice treatment. In contrast, the losses were equivalent to only 0.3% to 0.8% of the applied N in the PMRF treatment. Ammonia emissions were greatest during the first two weeks after sowing. Emissions before winter accounted for 82% of total NH3 emission in the conventional practice treatment, but only 49% to 61% of the total NH3 emission in the PMRF treatment. The soil NH4+ -N content and the soil moisture content had direct effects on NH3 emission before winter in the conventional treatment. In thePMRF treatment, the soil NH4+ -N content had a direct effect on NH3 emission before winter, whereas soil surface temperature and soil moisture had indirect effects. Ammonia emissions after the greening stage were mainly influenced by the soil NH4+ -N content. Simulation results indicated that logarithmic functions best described cumulative NH3 emission in the PMRF + high N rate treatment and the conventional treatment. A linear function best described cumulative NH3 emission in the PMRF + low N rate treatment and the unfertilized treatment. In conclusion, the PMRF treatment can significantly reduce N losses from winter wheat fields by changing the spatial-temporal dynamics of soil NH3 volatilization.

[Effects of seeding rate and nitrogen fertilization rate on physiological traits of winter wheat after anthesis in a field with plastic mulched rides and unmulched furrows].

Taking winter wheat cultivar Xiaoyan 22 as test material, a field experiment with central composite rotatable design was conducted to investigate the effects of seeding rate and nitrogen (N) fertilization rate on the physiological traits of the cultivar after anthesis under ridge-furrow cultivation with plastic film mulching, aimed to harmonize the relationships between winter wheat population and its individuals and to fully use the advantages of ridge-furrow cultivation in dry land areas. With increasing N fertilization rate, the leaf area index and the flag leaf chlorophyll content and net photosynthesis rate after anthesis increased; with increasing seeding rate, the leaf area index increased first and was stable then at early and middle milking stages but decreased at later milking stage, the flag leaf chlorophyll content and net photosynthesis rate decreased, and the grain yield per plant increased after an initial decrease. Appropriate seeding rate could optimize the relationships between winter wheat population and its individuals, and optimal N fertilization rate benefited the improvement of winter wheat physiological traits after anthesis and the enhancement of winter wheat yield. Under our experimental condition, seeding rate 112.5 kg x hm(-2) plus N fertilization rate 180-222 kg N x hm(-2) is a scheme beneficial to optimize the relationships between winter wheat population and its individuals and to establish a good winter wheat community structure with a reasonable leaf area index after anthesis, higher flag leaf chlorophyll content and net photosynthesis rate, higher grain yield per plant, and high yield per unit area.