Crop residue,manure and fertilizer in dryland maize under reduced tillage in northern China: I grain yields and nutrient use efficiencies

The rapidly increasing population and associated quest for food and feed in China has led to increased soil cultivation and nitrogen (N) fertilizer use, and as a consequence to increased wind erosion and unbalanced crop nutrition. In the study presented here, we explored the long-term effects of various combinations of maize stover, cattle manure and nitrogen (N) and phosphorus (P) fertilizer applications on maize (Zea mays L.) yield and nutrient and water use efficiencies under reduced tillage practices. In a companion paper, we present the effects on nutrient balances and soil fertility characteristics. The ongoing factorial field trial was conducted at Shouyang Dryland Farming Experimental Station in northern China from 1993 onwards. The incomplete, determinant-optimal design comprised 12 treatments, including a control treatment, in duplicate. Grain yields and N, P, and potassium (K) uptakes and N, P and K use efficiencies were greatly influenced by the amount of rain during the growing season (GSR), and by soil water at sowing (SWS). There were highly significant interactions between GSR and added stover and manure, expressed in complex annual variations in grain yield and N, P and K use efficiencies. Annual mean grain yields ranged from 3,000 kg ha⁻¹ to 10,000 kg ha⁻¹ and treatment mean yields from 4,500 kg ha⁻¹ to 7,000 kg ha⁻¹. Balanced combination of stover (3,000–6,000 kg), manure (1,500–6,000 kg) and N fertilizer (105 kg) gave the highest yield. Stover and manure were important for supplying K, but the effects differed greatly between years. Overall mean N recovery efficiency (NRE) ranged from 28% to 54%, depending on N source. NRE in wet years ranged from 50% to 90%. In conclusion, balanced combinations of stover, manure and NP fertilizer gave the highest yield and NRE. Reduced tillage with adding stover and manure in autumn prior to ploughing is effective in minimizing labor requirement and wind erosion. The potentials of split applications of N fertilizer, targeted to the need of the growing crop (response farming), should be explored to further increase the N use efficiency.     

砂质潮土施用有机肥后效研究

采用长期定位试验 ,研究了砂质潮土一次性施入不同数量有机肥对数年小麦的产量效应、产量构成、品质、水分利用和土壤肥力的变化和影响 .结果表明 ,有机肥不仅能显著增加当季小麦产量、单位面积穗数和穗粒数 ,提高耕层土壤有机质、全氮、有效磷、有效钾含量和水分利用效率 ,而且有较长的后效 .小麦产量与有机肥用量的关系 ,随着时间的推移 ,由二次曲线回归效应转变为直线相关 ;小麦粗蛋白质、干湿面筋含量与有机肥用量呈显著正相关     

不同施肥措施对土壤硝态氮垂直分布的特征影响

通过田间试验研究了冬小麦收获后NO3--N在土壤剖面中的累积状况。研究结果表明:不论是单独施用无机、生物有机肥还是无机、有机肥混施都会造成硝酸盐在土壤中的积累,但有机肥本身产生的硝酸盐累积量极微。生物有机、元机肥混施后减少了无机肥料中硝态氮深层累积。在0-100cm土层中,硝态氮的累积量呈递减趋势,在0-40cm的累积量最高。砂质土壤比牯质土壤更有利于硝态氮的深层迁移。     

Net N immobilisation during the biodegradation of mucilage in soil as affected by repeated mineral and organic fertilisation

Repeated fertilisation of crops with manure commonly increases both the amount and the quality of soil organic matter, the mineralisation of which strongly determines the availability of N to plants. In the rhizosphere, the microbial mineralisation/immobilisation of N is enhanced due to rhizodeposition (release of organic compounds from roots). In this work, we studied N transformations during incubation of maize root mucilage in soils that had been previously fertilized with composted pig manure or with ammonium nitrate for 7 years. Our work revealed mucilage was rapidly mineralised (average half-life of 3 days), inducing a rapid N immobilisation of 94 mg N g⁻¹ of mucilage C, followed by a slow remineralisation. Fertilisation with manure induced a persistent stimulation of the soil organic matter mineralisation, leading to an enhanced content of soil inorganic N (+23% in 58 days of incubation). Due to this stimulation of microbial activity in the soil fertilized with manure, the decrease in inorganic N during the biodegradation of mucilage lasted a shorter time as compared to the mineral fertilisation. However, the type of fertilisation did not significantly change the amount of N immobilised.     

有机肥对晒烟生理生化特性的影响

研究了不同种类的有机肥及配施方法对晒烟生理生化特性的影响。结果表明 ,农家肥和饼肥分别加化肥施用或两者混合加化肥施用均能明显降低烟叶中多酚氧化酶 (PPO)的活性 ;农家肥与饼肥混合并加化肥施用还能增加烟叶中叶绿体色素的含量 ,明显提高脯氨酸 (Pro)含量 ,降低丙二醛(MDA)含量 ,大幅度提高硝酸还原酶 (NR)活性 ,有利于改善烟叶品质和提高烟株抗逆性。因此 ,有机肥施用以农家肥与饼肥混施效果最佳。     

Modeling of ammonia speciation in anaerobic digesters

Anaerobic digestion of high-nitrogen wastes such as animal manure can be inhibited by high concentrations of un-ionized ammonia, NH₃ (aq). Understanding the toxicity of NH₃ (aq) to anaerobic digestion requires a method for determining its concentration. Previous work on ammonia toxicity in anaerobic digesters has utilized a simple equilibrium calculation for estimating NH₃ (aq) concentration from total ammonia, temperature, and pH. This approach is not appropriate for concentrated solutions. In this work, a speciation model for major solutes in anaerobic digesters, based on Pitzer's ion-interaction approach, is presented. Model simulations show that the simple equilibrium calculation (without corrections for non-ideal behavior) substantially overestimates NH₃ (aq) concentration for all but dilute digesters. This error in concentration determination increases with total solids content and is estimated to be greater than 40% for a digester fed dairy manure with 5% total solids or swine manure with 3% total solids. However, including an estimate of the activity coefficient for NH₄⁺ in the simple equilibrium calculation results in much more accurate estimates of NH₃ (aq) concentration. In this case, the estimated error is less than 10% in the absence of struvite precipitation at the highest total solids contents considered.     

Spatial and temporal variability in excessive soil phosphorus levels in eastern North Carolina

Numerous studies have shown that accumulation of excessive soil phosphorus raises the potential for phosphorus export and eutrophication of adjacent surface waters. Soil phosphorus data from the North Carolina Agronomy Division's database were analyzed for two-year periods spanning the decades of the 1980s and 1990s for 39 eastern North Carolina counties. Eastern North Carolina supported extensive row crop agriculture, rapidly growing intensive livestock industries, and a growing human population during these decades. Excessive soil phosphorus levels, defined as having a soil phosphorus index (P-I, based on Mehlich III testing) > 100, occurred in over 40% of almost a million samples reported for the three two-year periods analyzed. Excessive soil P-I levels were most frequent in central eastern North Carolina, declined in the 1980s and rose again in the 1990s. The distribution of row crop area with excessive soil P-I levels was very similar in time and space. Increases in the area harvested for cotton (+635%) and pasture (+523%) with excessive soil P-I levels were particularly large during the 1990s, when crop areas harvested associated with excessive soil P-I levels for other major crops (corn, tobacco, peanuts) declined. Residential and recreational land uses were associated with similarly high frequencies of excessive soil P-I levels, but these land uses were relatively unimportant (<5% area) compared to agricultural land use (~34%) in the region. Recent increases in fertilizer shipments (approximately twofold in the late 1990s) likely reflected increased cotton production. Rapid growth in concentrated animal production (almost twofold increase in total animal units (AU) between 1992 and 2001), with accompanying land application of wastes, accounted for increases in soil P-I values in pasturelands in the 1990s, particularly in central eastern North Carolina, where these activities were concentrated. The potential threat to water quality from export of excessive soil phosphorus is therefore greatest in this region. North Carolina is currently developing a Phosphorus Loss Assessment Tool (PLAT) in an attempt to manage the challenge posed by excessive soil phosphorus levels.     

Effect of cattle manure on selenate and selenite retention in soil

The aim of the present investigation was to study the effect of manure on retention of selenium (Se) in soil. Addition of cattle manure in combination with selenite and selenate reduced the adsorption of both anions to a loam soil in a batch experiment. The results were explained by the content of low-molecular-weight organic acids in the manure which compete with Se for the sorption sites. In a pot experiment with loam and peat soils and with two pH levels within each soil, cattle slurry added together with selenate was found to increase the Se concentration in grain at the highest pH level (6.1 and 6.8 for the loam and peat, respectively). At a lower pH (5.4 and 6.0 for the loam and peat, respectively) there was no significant effect of slurry on Se concentration in grain. Application of slurry also increased the residual effect of Se applied to the loam soil in the preceding growing season. In the peat soil, no residual effect of Se was found either with or without the addition of slurry.     

Dung pads increase pasture production,soil nutrients and microbial biomass carbon in grazed dairy systems

In grazing systems dung is an important source of nutrients which can increase soil fertility and contribute to nutrient cycling through increased pasture production. Changes in soil chemical and biological properties and pasture production were measured below and around dung pads created in the field. Almost 65% of the total dung P remained after 45 days and about two-thirds of the pad fresh weight had disappeared in that time, indicating that physical degradation is the mechanism of incorporation of dung P. All the pads bar one were completely degraded by 112 days. At this time, soil pH and EC increased under dung pads as did Olsen extractable inorganic phosphorus (Pi) and total phosphorus (Pt), with these changes observed at 0–5 and 5–10 cm depths. Bicarbonate extractable soil organic phosphorus (Po) was not affected by dung and the observed differences in soil Po:Pi ratios were largely influenced by the substantial addition of inorganic P from dung. Dung increased the P buffering capacity of the 0–5 cm soil samples collected at the end of the experiment, potentially contributing to the increased extractable soil P measured under the pads. Dung also changed soil properties in 0–10 cm samples with increases in soil pH, EC, Colwell P and Colwell K recorded even long after the dung had completely disappeared. Microbial biomass carbon increased under dung pads in the 0–10 cm soil samples in the first 45 days after pads were applied. Total herbage production and ryegrass biomass increased significantly under and around the pads by 112 days after dung was applied. The botanical composition changed significantly with increased ryegrass contents observed, but only under the dung pads. This experiment demonstrated that increases in pasture around dung pads in the field are not solely due to animal rejection.     

Comparison of the ozonation and Fenton process performances for the treatment of antibiotic containing manure

An integrated treatment method based on magnesium salt extraction followed by chemical oxidation was used for the treatment of a veterinary antibiotic, oxytetracycline (OTC) contaminated cow manure since animal manure can be an important source for antibiotic pollution in the environment. Pretreatment with magnesium salt enhanced the efficiencies of subsequent oxidation processes by extracting 63.9% of OTC from the manure thereby making it more favorable for oxidation with the hydroxyl radicals produced by the Fenton and ozone oxidation processes. Both the 24 h Fenton oxidation process with 434 mM H₂O₂ and 43.4 mM Fe²⁺ doses and the 1-h ozonation process with an applied ozone dose of 2.5 mg min^− 1 provided more than 90% OTC removal from the manure slurry. However, the second-order OTC removal rate constant of Fenton process (119 M^− 1s^− 1) was remarkably lower than that obtained with the ozonation process (548 M^− 1s^− 1). The oxidant dose was a significant factor for the efficiency of the Fenton treatment but not for the ozone treatment. The efficiencies of both the Fenton and ozone oxidation processes were not affected by the pH adjustment of the manure slurry.