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Effects Of Conservation Tillage On Water And Nitrogen Use In Rainfed Winter Wheat And Soil Ammonia Volatilization In Loess Plateau

Posted on:2016-09-26Degree:DoctorType:Dissertation
Country:ChinaCandidate:Y YangFull Text:PDF
GTID:1223330461466866Subject:Fertilizer learn
Abstract/Summary:PDF Full Text Request
Rain-fed winter wheat production in Loess Plateau of China is highly dependent on water and nutrient(e.g., nitrogen) supply. However, water and nitrogen supply in this region is limited. With conventional tillage practice and nitrogen fertilization, wheat yield can be increased, but leading to nitrogen losses and ammonia volatilization; meanwhile, it can cause high consumption of soil water, impeding the sustainable development of winter wheat production in the region. Conservation tillage practices can improve the water status and nutrient supply in field conditions. Therefore, conservation tillage is recommended in rain-fed crop production. However, little is known about the mechanisms of conservation tillage on grain yield, water use, nitrogen use and ammonia volatilization in rain-fed winter wheat fields in Loess Plateau of China. A three-year experiment was conducted in Yangling during 2011-2014 winter wheat growing seasons. The experiment followed a split-plot design with three replicates, with tillage systems as the main plots, consisted of one conventional tillage(CT) and five conservation tillage practices, namely stalk mulching(SM), film mulching(FM), ridge tillage(RT), ridge tillage with film mulch on the ridge(RTf), ridge tillage with film mulch on the ridge and stalk mulch in the furrow(RTfs); while with nitrogen fertilization treatments as the subplots, consisted of N0(without nitrogen fertilization) and N180(fertilized at 180 kg N ha-1) treatments. The effects of conservation tillage practices on grain yield and yield components, plant morphology and assimilative capacity, water use, nitrogen uptake, nitrogen translocation, nitrogen use, available nitrogen dynamics, microbial biomass nitrogen, and ammonia volatilization were analyzed. The findings in this study can help reveal the mechanisms of conservation tillage on grain production, water and nitrogen use, and soil ammonia volatilization in rain-fed winter wheat fields in this region. The main results are listed as follows:a) Grain yield was positively correlated with grain sink, spike density and grain number per spike(P < 0.01). Conservation tillage practices significantly increased grain sink, harvest index and grain number per spike(P < 0.05). Grain yield in conservation tillage treatments averaged 3862 ~ 4270 kg ha-1, 4.2% ~ 15.2% greater than that in conventional tillage(3705 kg ha-1). Grain yield ranged as: film mulching(FM) > ridge tillage with film mulch on the ridge and stalk mulch in the furrow(RTfs) > stalk mulching(SM) > ridge tillage with film mulch on the ridge(RTf) > ridge tillage(RT) > conventional tillage(CT). Nitrogen fertilization significantly increased grain sink and spike density(P < 0.05). Grain yield in N180 treatment averaged 5045 kg ha-1, 70.4% greater than that in N0 treatment(2961 kg ha-1, P < 0.05).b) Grain yield was positively correlated with biomass, leaf area index, leaf chlorophyll and carotenoid content(P < 0.01 or P < 0.05). With tillage practices and nitrogen fertilization, leaf area index, leaf chlorophyll and carotenoid content could be regulated. Conservation tillage practices affected wheat growth by regulating morphological and assimilative parameters. Nitrogen fertilization significantly increased leaf area index and leaf chlorophyll content, thus increased assimilative capacity and biomass significantly(P < 0.05).c) Grain yield was positively correlated with soil evapotranspiration, water use efficiency and canopy moisture(P < 0.01). Soil evapotranspiration, water use efficiency and canopy moisture could be regulated with conservation tillage practices and nitrogen fertilization. Conservation tillage practices significantly decreased soil evapotranspiration, and increased water use efficiency and canopy moisture. Water use efficiency in conservation tillage treatments averaged 13.3 ~ 15.6 kg ha-1 mm-1, 16.7% ~ 36.8% greater than that in conventional tillage(11.4 kg ha-1 mm-1, P < 0.05). Nitrogen fertilization increased soil evapotranspiration, water use efficiency and canopy moisture. Water use efficiency in N180 treatment averaged 16.6 kg ha-1 mm-1, 55.1% greater than that in N0 treatment(10.7 kg ha-1 mm-1, P < 0.05).d) Grain yield was positively correlated with nitrogen uptake, apparent nitrogen recovery, agronomic nitrogen efficiency, vegetative organ(leaf, stem and shell) nitrogen translocation amount, stem nitrogen translocation efficiency and leaf nitrogen contribution ratio(P < 0.01). Grain yield was negatively correlated with shell nitrogen translocation efficiency and shell nitrogen contribution ratio(P < 0.01). Nitrogen uptake, nitrogen harvest index, and vegetative organ nitrogen translocation amount and efficiency, and vegetative organ nitrogen contribution ratio could be regulated with tillage practices and nitrogen fertilization. Conservation tillage practices increased nitrogen uptake. Nitrogen uptake in most conservation tillage treatments averaged 74.0 ~ 101.1 kg N ha-1, 0.3% ~ 37.0% greater than that in conventional tillage(73.8 kg N ha-1). Conservation tillage practices increased nitrogen harvest index and leaf nitrogen translocation amount, nitrogen uptake, stem nitrogen translocation efficiency and shell nitrogen translocation efficiency, but reduced leaf and shell nitrogen contribution ratio, shell nitrogen translocation amount and leaf nitrogen translocation efficiency. Nitrogen fertilization significantly increased nitrogen uptake and vegetative organ nitrogen translocation amount and leaf nitrogen contribution ratio(P < 0.05), while significantly reduced nitrogen harvest index, vegetative organ nitrogen translocation efficiency, stem nitrogen contribution ratio and shell nitrogen contribution ratio(P < 0.05).e) In N180 treatments, the maximum and mean of soil ammonium, nitrite and nitrate concentration in conservation tillage treatments were greater than that in conventional tillage(CT) treatment. In N0 treatment, soil ammonium and nitrite concentration in conservation tillage treatments were similar to that in CT treatment, but soil nitrate concentration was higher than in CT treatment.f) Soil microbial nitrogen could be regulated by tillage practices and nitrogen fertilization. Most conservation tillage practices reduced soil microbial nitrogen. In N180 treatments, conservation tillage practices reduced soil microbial nitrogen, thus promoted organic nitrogen conservation in the soil; in N0 treatments, several conservation tillage increased soil microbial nitrogen, therefore promoted the mineralization of soil organic nitrogen, leading to increases in available nitrogen. Nitrogen fertilization significantly increased soil microbial nitrogen(P < 0.05).g) Soil ammonia volatilization peaked during the first 10 d after fertilizing and sowing, and leveled off after the next 20 d. Ammonia volatilization averaged 3.25 ~ 7.45 kg N ha-1 each wheat growing season. Nitrogen fertilization significantly increased ammonia volatilization, and significantly decreased ammonia volatilization intensity(P < 0.05). In N180 treatments, conservation tillage practices reduced ammonia volatilization amount and ammonia volatilization intensity; in N0 treatment, stalk mulching(SM) and three ridge tillage practices increased ammonia volatilization amount, and film mulch(FM) decreased ammonia volatilization intensity. Ammonia volatilization ranged as: film mulching(FM) < ridge tillage(RT) < ridge tillage with film mulch on the ridge(RTf) < ridge tillage with film mulch on the ridge and stalk mulch in the furrow(RTfs) < stalk mulching(SM) < conventional tillage(CT). Soil ammonium, soil moisture and soil temperature were the three major soil environmental factors affecting ammonia volatilization. Fertilizer ammonia loss in conservation tillage treatments averaged 0.65 ~ 1.65 kg N ha-1, 41.9% ~ 77.1% lower than that in conventional tillage(2.84 kg N ha-1), where, film mulching(FM) led to the lowest fertilizer ammonia loss and ammonia volatilization intensity.In general, conservation tillage practices can increase grain yield, water and nitrogen use efficiency in rain-fed winter wheat and reduce ammonia volatilization in this region. Hence, conservation tillage practices are recommended in the rain-fed winter wheat growth regions in Loess Plateau of China. In which, film mulching(FM) treatment is specially recommended since it led to the highest grain yield and the lowest ammonia loss.
Keywords/Search Tags:ammonia volatilization, nitrogen use efficiency, water use efficiency, ridge tillage, film mulching
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