Nitrous oxide emission from upland crops and crop-soil systems in northeastern China

Although it is known that crops can directly emit N₂O, their contribution to the total N₂O emission from crop-soil systems under field conditions is not well understood. This study was conducted to study the contribution of crops to total N₂O emission from soybean-soil and maize-soil systems in northeastern China. The effects of N fertilization on N₂O emission and NO ₃ ⁻ -N concentration in plants were also studied. The emission from crop-soil systems was measured with the closed chamber method, whereas the direct emission from crops was measured with the soil surface-sealed method. The addition of fertilizer N significantly increased the NO ₃ ⁻ -N concentration in crops and enhanced the N₂O emission from crop-soil systems and from crops alone. The amount of N₂O emitted directly from soybean plants accounted for 6 to 11% of the total soybean-soil emission. Similarly, the amount of N₂O emitted directly from maize plants accounted for 8.5 to 16% of the total maize-soil emission. The proportion of the applied N lost through direct N₂O emission from plants ranged from 0.19 to 0.34%, whereas the proportion of the applied N lost through N₂O emission from the crop-soil system ranged from 1.1 to1.9%. These results suggest that the use of chambers that do not include plants may lead to an underestimation of the total N₂O emission from crop-soil systems. This revised version was published online in November 2006 with corrections to the Cover Date.     

A Comparison of the Levels of Lutein and Zeaxanthin in Corn Germ Oil,Corn Fiber Oil and Corn Kernel Oil

All commercial corn oil is obtained by pressing corn germ and/or extracting the germ with hexane. In the current study, six types of corn oil were prepared by extracting corn germ, corn fiber and ground corn, each with hexane or with ethanol. The levels of lutein, zeaxanthin and other carotenoids were quantitatively analyzed in the six corn oils. The levels of lutein + zeaxanthin in the oil ranged from 2.3 μg/g for hexane-extracted corn germ oil to 220.9 μg/g for ethanol-extracted ground corn oil. These results indicate that a diet that includes 30 g (~2 tbsp) per day of the unrefined corn oil obtained by extracting ground corn with ethanol would provide ~6 mg of lutein + zeaxanthin, the daily dosage that is currently considered to be necessary to slow the progression of age-related macular degeneration. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture.     

硼在玉米中的分布特征及化学形态的研究

对施硼肥和不施硼肥的土壤上种植的玉米中硼的分布及化学形态进行了研究 ,结果表明 ,靠近根部的玉米叶子中含硼最多 ,中部和上部叶子中含硼量依次递减 ,玉米种子中的含硼量低于叶子中的含硼量。通过研究不同溶剂对玉米叶子和种子中硼的浸提能力 ,探明了以 10 %醋酸浸提下来的硼最多 ,其次是用 0 .0 1mol/LEDTA浸提下来的硼 ,用水浸提下来的硼的含量最少。     

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.     

基于二分内包围盒的玉米光照逆光线跟踪算法

为了在玉米仿真中构建逼真有效的光环境,提出一种基于二分内包围盒的玉米光照逆光线跟踪算法。首先,在玉米表面建立二分内包围盒进行预处理,减少光线与玉米相交运算量;其次,引入遮挡因子简化光能计算的复杂度;最后,通过调整光能阈值达到光环境逼真度和算法效率的统一。为了验证算法的快速有效性,建立玉米模型,对比不同包围盒求交运算的速率,得出二分内包围盒的求交速度最快,逆光线跟踪算法模拟出的玉米生长效果较为逼真。     

A Two-Step Filtering approach for detecting maize and soybean phenology with time-series MODIS data

The crop developmental stage represents essential information for irrigation scheduling/fertilizer management, understanding seasonal ecosystem carbon dioxide (CO₂) exchange, and evaluating crop productivity. In this study, we devised an approach called the Two-Step Filtering (TSF) for detecting the phenological stages of maize and soybean from time-series Wide Dynamic Range Vegetation Index (WDRVI) data derived from Moderate Resolution Imaging Spectroradiometer (MODIS) 250-m observations. The TSF method consists of a Two-Step Filtering scheme that includes: (i) smoothing the temporal WDRVI data with a wavelet-based filter and (ii) deriving the optimum scaling parameters from shape-model fitting procedure. The date of key crop development stages are then estimated by using the optimum scaling parameters and an initial value of the specific phenological date on the shape model, which are preliminary defined in reference to ground-based crop growth stage observations. The shape model is a crop-specific WDRVI curve with typical seasonal features, which were defined by averaging smoothed, multi-year WDRVI profiles from MODIS 250-m data collected over irrigated maize and soybean study sites.In this study, the TSF method was applied to MODIS-derived WDRVI data over a 6-year period (2003 to 2008) for two irrigated sites and one rainfed site planted to either maize or soybean as part of the Carbon Sequestration Program (CSP) at the University of Nebraska-Lincoln. A comparison of satellite-based retrievals with ground-based crop growth stage observations collected by the CSP over the six growing seasons for these three sites showed that the TSF method can accurately estimate the date of four key phenological stages of maize (V2.5: early vegetative stage, R1: silking stage, R5: dent stage and R6: maturity) and soybean (V1: early vegetative stage, R5: beginning seed, R6: full seed and R7: beginning maturity). The root mean square error (RMSE) of phenological-stage estimation for maize ranged from 2.9 [R1] to 7.0 [R5] days and from 3.2 [R6] to 6.9 [R7] days for soybean, respectively. In addition, the TSF method was also applied for two years (2001 and 2002) over eastern Nebraska to test its ability to characterize the spatio-temporal patterns of these key phenological stages over a larger geographic area. The MODIS-derived crop phenological stage dates agreed well with the statistical crop progress data reported by the United State Department of Agriculture (USDA) National Agricultural Statistics Service (NASS) for eastern Nebraska's three crop agricultural statistic districts (ASDs). At the ASD-level, the RMSE of phenological-stage estimation ranged from 1.6 [R1] to 5.6 [R5] days for maize and from 2.5 [R7] to 5.3 [R5] days for soybean.     

喷洒有效微生物群对玉米抗旱性的影响

采用孕穗期干旱处理前喷施有效微生物群（ＥＭ）研究干旱对玉米叶片膜脂过氧化和抗性酶及产量的影响。结果表明：ＥＭ能明显降低ＭＤＡ含量，提高ＳＯＤ和ＣＡＴ活性，增强玉米的抗旱性并提高产量。     

Capillary electrophoretic profiling of tryptic digests of water soluble proteins from Bacillus thuringiensis-transgenic and non-transgenic maize species

Capillary zone electrophoresis (CZE) has been applied to separation and characterisation of enzymatic (tryptic) hydrolysates of water-soluble proteins from Bacillus thuringiensis (Bt)-transgenic (Aristis-Bt) and two native non-transgenic (Aristis and Coventry) maize varieties. Water-soluble proteins were extracted from the flour of these maize species and digested by bovine pancreatic trypsin immobilised on agarose gel in 100 mM ammonium hydrocarbonate buffer, pH 7.9. The yielded tryptic digests of proteins were analysed by CZE in four acidic background electrolytes (BGEs) (100 mM H₃PO₄, 50 mM Tris, pH 2.25; 500 mM acetic acid, pH 2.54; 200 mM formic acid, 200 mM acetic acid, pH 2.05; and 200 mM iminodiacetic acid, pH 2.26) using a lab-made CZE apparatus equipped with bare fused silica capillary and UV-absorption detector operating at 206 nm. Among the tested BGEs, the best resolution of the tryptic peptides of extracted proteins of the above three maize species was obtained in isoelectric BGE, 200 mM iminodiacetic acid, pH 2.26. Selected resolved tryptic peptides of proteins were characterised by effective electrophoretic mobilities and corrected (migration times normalised) peak areas. Some significant relative qualitative and quantitative differences in CZE-UV profiling of tryptic protein digests were found, which can be potentially used to differentiate transgenic Aristis Bt and non-transgenic Aristis varieties or two native non-transgenic varieties, Aristis and Coventry.     

Chlorpyrifos residue levels on field crops (rice,maize and soybean) in China and their dietary risks to consumers

In this study, chlorpyrifos residue levels in field crops of rice, maize and soybean were investigated according to the “Guideline on Pesticide Residue Trials” of China. On the basis of the residual results, human dietary risks were further evaluated. Chlorpyrifos residues of harvest grains were firstly prepared by QuEChERS method and analyzed using Gas Chromatography Tandem Mass Spectrometry (GC–MS/MS). Dietary risks were assessed by a deterministic approach. The median residues in field trials of rice, maize and soybean were 0.617, 0.0227 and 0.0136 mg kg⁻¹, respectively. The highest residues in field trials of rice, maize and soybean were 3.23, 0.114 and 0.102 mg kg⁻¹, respectively. Chronic intake assessment indicated that only 39.0% of acceptable daily intake (ADI, 0–0.01 mg kg bw⁻¹ day⁻¹) was consumed through rice, maize and soybean. The acute hazard indexes (aHI) of adults was 26.1% of acute reference dose (ARfD, 0–0.1 mg kg bw⁻¹) and aHI of children was 63.5% of ARfD in dietary exposure assessment through rice, maize and soybean consumption. Single pathway risk assessment indicated that chlorpyrifos application on field crops in manner of the good agricultural practices didn't pose public health risks.