Erosional impact on organic matter content and productivity of selected Iowa soils

From 1983 to 1989 an erosion-productivity study was conducted in Iowa. The primary objective of this project was to determine the effects of accelerated erosion and its interactions with other variables on soil productivity, as measured by corn yields of loess and till-derived soils in Iowa. Multiple regression techniques were used to relate corn yields to erosion and selected soil, climatic, and weather variables. Organic matter content of the soils was significantly correlated with erosion phase. Yields of till-derived soils decreased more with increasing degree of erosion than loess-derived soils. The conclusions are based on data collected at 569 sites located in 44 Iowa counties.     

Nutrient content of earthworm casts influenced by different mulch types

The aim of this study was to investigate the effects of different mulch types on the quality and quantity of casts of different lumbricid earthworm species. Nutrient contents (organic carbon C_org, total nitrogen N_t and inorganic phosphate Pi), and acid phosphatase activity (SPA) of earthworm casts and soil aggregates were measured and then compared. This short time experiment was conducted in the laboratory, simulating field conditions of mulch management in temperate agroecosystems. In microcosms, the two common field species Lumbricus terrestris and Octolasion cyaneum were inoculated. Barley, lupin, maize, or sugarbeet were used as mulch according to amounts usually applied in the field. Nutrient contents and phosphatase activity in worm casts were generally enhanced compared to the soil. Nutrient values were higher in the casts of the detritivorous L. terrestris than those of the geophageous O. cyaneum. Conversely, the phosphatase activity was increased in the casts of O. cyaneum compared to L. terrestris in case of the barley and sugar-beet treatments. Cast production was related to the earthworms' change of biomass (ΔB) as well as, in the case of L. terrestris, to nitrogen content of the mulch. Due to their chemical compounds, the mulch types influence both the food selection of the worms and the acceptance by microorganisms.     

Nutrient content of Kenaf (Hibiscus cannabinus) at five growth stages

Abstract

Kenaf (Hibiscus cannabinus) grown during the wet season in the Ord Irrigation Area of Western Australia was sampled at five growth stages. The samples were separated into bark, wood, tops plus foliage and, where applicable, seed. Each fraction was analysed for zinc, manganese, iron, copper, sodium, potassium, calcium and magnesium by atomic absorption spectroscopy, and for nitrogen and phosphorus by colorimetry. Concentrations of these elements in each plant fraction are presented. Calculation of total above‐ground nutrient content of the crop indicated a high content of potassium throughout the growth cycle (up to .280 kg/ha), an initially high content of nitrogen (150 kg/ha) stabilising at a lower level (about 75 kg/ha) up to maturity, and an increasing content of zinc (150 g/ha to 350 g/ha) and calcium (65 kg/ha to 105 kg/ha) with age. A higher content of iron at maturity was also apparent (up to 1400 g/ha). A comparison with other reported data is made.     

自然降水条件下煤矸石坡土壤含水量及径流变化

为了防止矸石山水土流失,促进煤矿废弃地植被恢复,对自然降水条件下煤矸石坡面含水量及径流变化进行观测,研究降水量及风化年限对煤矸石坡面各层含水量及产流量的影响.结果表明:1)在小雨(＜10 mm/d)条件下,煤矸石坡地表、地下径流量接近;在中雨(≥10 mm/d,＜25 mm/d)及大雨(≥25 mm/d)条件下,降雨主要以地下径流的形式流失.在小雨情况下,煤矸石坡产生的地表径流、地下径流量均较少;中雨的发生频率和累计降水量最高,累计产生的地表径流量最高;大雨发生频率最低,累计产生的地下径流量和总径流量最高.2)地表径流量与降水量显著正相关,地下径流量与最大降雨强度、平均降雨强度显著正相关.3)由于风化程度增加,与2013年相比,2014年次小雨产生的地表径流、地下径流和总径流分别降低50％、100％、80％,次中雨产生的地表径流、地下径流和总径流分别降低88％、82％、97％.4)煤矸石具有一定的蓄水能力,20 ～ 30 cm含水量最高.随着风化程度增加,10 ～ 30 cm含水量增加.尽管10 cm风化程度高,但是由于表层蒸发,含水量较低.5)由于煤矸石颗粒粗大、渗透性强,在小雨、中雨、大雨条件下,矸石坡产生的地表径流量均小于土坡,分别为土坡的4％、26％、19％.     

Changes in water content in and under frozen soil in Iowa,U.S.A.

Water contents were measured in a soil profile during the winter from the time of harvest until soil temperatures were greater than 0°C through this profile in the spring. Water movement between successive layers was predicted using the Darcy flow law and changes in water flux. These values were then compared with the changes in soil water content observed in field measurements. Results showed that water content changes (accumulation or loss) below the frozen layer were greater than predicted but that the differences between predicted and measured contents were small, much smaller than the amounts reported in previous experiments.     

Variations in the acid content of rain water in the course of a single precipitation

The major acid components in the rain water collected during five different rainfall events in July and August 1977, were found to be a strong acid, the weak acid NH _in4 ^su+ and dissolved CO₂ from the atmosphere. Variations in their concentrations were determined as a function of time in the course of each of the rainfall events. Two experimental methods were used in this investigation, a microtitrim etric method and a coulometric method, and the data were analyzed by the use of modified Gran functions. Both methods gave the same results. The most significant observation was that the strong acid concentration increased from very low values to a maximum and then decreased in the course of a single rainfall event.     

北京密云油松人工林对降水及其营养元素含量的影响

对北京密云水库库西油松人工林的林冠截留、穿透降水和树干茎流的观测和分析结果表明，单次降雨过程中的林冠截留量与林外降水量呈幂函数关系，而穿透雨量和树干茎流量跟林外降水量皆呈线性相关关系，它们占林外降水的比例分别为7．23％～87．39％，12．56％～91．58％和0．007％～1．77％。环境状况、气象条件和降水特性的不同是造成同一地区大气降水化学性质差异的主要原因；降水透过油松林冠层后，穿透降水和树干茎流中元素含量都有不同程度的增加。穿透降水中各元素含量变化均与降水时间间隔呈正相关，而与降雨强度和降水量呈负相关；除N外，树干茎流中P，K元素含量与降水特性的关系与穿透降水的相同。     

0～50 cm土壤含水量与降水和蒸发的关系分析

利用濉溪县0～50cm土层土壤含水量和同期降水量、蒸发量资料分析表明，土壤水分的主要活动层在耕层，不同层次土壤含水量之间存在极显著的正相关。土壤含水量增减与期间降水量、蒸发量呈直线相关关系，耕层土壤含水量变化和报告期与基期的比值均与湿润系数呈极显著正相关。0～30cm不同层次土壤相对含水量低于50％时，需降水或补充灌溉13．6～39．0cm方可使耕层相对含水量达到80％。当湿润系数为0．47时，耕层土壤含水量可以维持在基期水平。耕层土壤含水量蒸减呈“快-缓慢-滞缓”的变化过程，蒸减速率随土壤含水量的变化可用指数曲线拟合。使耕层相对含水量达到80％以上的一次降水过后，连续10．7～38．3d无降水，耕层相对含水量尚可维持在60％以上。     

基于CMORPH CRT产品的太行山区降水时空格局

为有效利用太行山区降水资源,实现科学的水资源管理和生态建设,本研究利用1998—2017年CMORPHCRT卫星降水产品数据探究山区降水的时空格局和变化趋势,并通过18个地面雨量站的数据验证山区多年来降水趋势变化。结果表明:在年尺度上, 1998—2017年太行山区年均降水量和各季节降水量无明显变化趋势,太行山区南坡和东坡降水量高于北坡和西坡;在月尺度上,7月是全年降水的主要贡献时段,占全年总降水量的7.2%～32.4%,其次是8月和6月。太行山区南部和西北部降水呈现下降趋势,年均降水量减少2～6mm;山区西部和北部降水呈现增长趋势,年均增加量大于8mm;7月是山区降水趋势差异最大的月份,趋势变化范围在-8.6～8 mm·a~(-1)。根据地面实测数据验证降水变化趋势,在年尺度上,两者数据计算得到的降水趋势呈现极显著相关(P0.01);在季节尺度上,冬季(干季)和夏季(湿季)降水趋势变化与地面实测数据的降水趋势具有极显著相关性(R=0.902,P0.001;R=0.550,P=0.018),但在春季和秋季相关性不显著。根据1998—2017年降水趋势的空间分布栅格图,提取每一栅格的像元值,再将提取所得的降水趋势(PT)划分为6个区间(PT≤-5 mm·a~(-1)、-5 mm·a~(-1)PT≤0 mm·a~(-1)、0 mm·a~(-1)PT≤5 mm·a~(-1)、5 mm·a~(-1)PT≤10 mm·a~(-1)、10 mm·a~(-1)PT≤15mm·a~(-1)和PT15mm·a~(-1)),在不同的趋势区间探索20年来的降水趋势变化特征,研究发现在降水趋势5mm·a~(-1)的区间,降水量从1998年到2017年呈现显著增加的趋势。基于高分辨率卫星数据阐明太行山区降水时空格局和变化趋势,能够为该区域水资源合理利用和生态恢复提供建议和支持。     

Phase transitions of pea starch over a wide range of water content

The phase transitions of pea starch over a wide range of water content were investigated by differential scanning calorimetry (DSC). Swelling of starch granules increased progressively with increasing water content. The main endotherm G broadened progressively with increasing water content up to 94.5 wt % (water:starch ratio 15:1), above which it became too broad to define. The corresponding peak and conclusion temperatures and enthalpy change increased with increasing water content. Scanning electron microscopy (SEM) showed that, at a water:starch ratio of 2:1 (water content of 70.7 wt %), starch granules only swelled partially with discernible granular contours still clearly evident. The results of swelling power tests and SEM images revealed that the endotherm G obtained at a water:starch ratio of 2:1 represented only partial swelling of starch granules. The transition from a narrow to broad endotherm G was interpreted to reflect the thermal transition behavior progressing from limited swelling to maximum swelling and then partial dissolution and leaching of starch polymers from the granules.     

Trace Element Concentrations of Iowa Surface Soils

Trace elements in the environment have received considerable attention in recent years. This study was carried out to assess the concentrations of 15 trace elements in 171 representative Iowa surface soils obtained from 30 counties, representing 41 major soil series in Iowa, which constitute 63.5% of the Iowa landscape. This was coupled with analysis of eight major elements. The trace metals were determined either by atomic absorption spectrophotometry or an argon plasma emission spectrometer in soil digests. The ranges, means, median, standard deviations, and frequency distribution of the elements studied are reported. Results showed that, in general, concentrations of the trace elements were significantly correlated (P < 0.01) with those of the major elements studied. With a few exceptions, the concentrations of trace elements were intercorrelated (P < 0.01), suggesting their presence in soils predominantly as mineral constituents.     

Quasi-biennial corn yield cycles in Iowa

Quasi-biennial cycles are often reported in climate studies. The interannual El Niño Southern Oscillation (ENSO) and North Atlantic Oscillation (NAO) are two phenomena containing quasi-periodicities of approximately 2.5 and 2.2 years. It is known that ENSO affects corn yield through weather patterns, NAO affects surface temperature and cloudiness, and surface temperature, rainfall, and radiation affect corn yield. However, a quasi-biennial pattern in corn yield and the combined effect of several climate signals on long-term U.S. corn yield are not known. Here we show statistically significant 2–3 year periods in long-term corn yield from one of the world's most important corn producing regions. High (low) yields are due in part to high (low) surface radiation and low (high) temperature early in the corn growing season coupled with sufficient (insufficient) rainfall later in the growing season. A statistical model we developed using three climate indices accounts for 54% of the interannual variation in Iowa corn yield. The most significant periodicities found in the model's spectrum are similar to the quasi-biennial periodicities in observed corn yield. We classify Iowa corn yield from several regional datasets (1960–2006) for ‘low yield’ and ‘high yield’ conditions as predicted by the model. The difference between observed corn yields for ‘high’ and ‘low’ yielding years was 19% (p = 0.0001). The results demonstrate a quasi-biennial pattern in long-term Iowa corn yield related to large-scale climate variability. This knowledge could lead to models that help guide springtime agricultural management decisions that improve profitability and reduce nitrate flux to groundwater, streams, rivers, and coastal oceans.     

Nutrient content of maize and soil organic matter status under various tillage methods and farmyard manure levels

Abstract

A two-year field study was conducted under semi-arid conditions in Pakistan to assess the role of tillage systems and farmyard manure on soil, plant nutrients and organic matter content. Four tillage systems (zero, minimum, conventional and deep tillage) and three farm manure levels were used. Maize crop was grown up to maturity. Uptake of N, P and K in maize shoots improved in tillage systems compared to non-tillage and treatments where farmyard manure was applied. Soil N status decreased in the deep tillage systems, whereas it increased in all other tillage systems and in the farmyard manure amended treatments. Increase in soil P values was observed under minimum and conventional tillage, whereas deep tillage resulted in a decrease. Farmyard manure amendments increased soil P and soil K in all systems. Tillage did not affect soil K levels. Results demonstrate that reduced tillage is practicable in arid and semi-arid regions since it improves soil fertility.     

Assessment of Iowa farmers' perceptions about auger safety

A survey of Iowa farmers was conducted to assess the farmers' perceptions and beliefs regarding auger safety and how these perceptions are put into practice. A questionnaire was designed to obtain information on the following auger-related topics: recognition of safe practices and appropriate shielding, personal practices and behaviors, risk perception, and personal beliefs. A random sample of 400 Iowa farmers (arrayed by county) was selected to be representative of Iowa farms. The response to the mailed survey was 23%. Some returned surveys were eliminated because the respondent was retired or did not own/operate augers, resulting in 57 usable questionnaires. Survey responses indicate that the majority of Iowa farmers who participated in this study can correctly identify appropriate shielding for auger intake that meet or exceed ASAE standards. Survey responses suggest that it is common practice in Iowa for youth (age 13 to 19) to operate augers. Iowa farmers in this study perceive the most important contributing factors to auger-related injuries to be operating an auger without shielding, failure to pay attention on the job, moving augers in a raised position, and using hand or feet to redirect the flow of grain. Survey results also indicate that carelessness is perceived to be the leading cause of auger-related injuries, and that auger related injuries can be avoided by having respect for the equipment, being careful, and using common sense. The results also show that the Iowa farmers who participated in this study commonly perform auger-related practices (e.g., moving an auger in a raised position) that they identify as being unsafe.     

Characterization of hydrocarbon spreading in an alluvial aquifer by cross correlation study of precipitation and contaminant content data

An accidental spillage of gasoline in a sector of the ‘Vega de Granada’ alluvial aquifer (Spain) affected a number of wells in the area. Hydrocarbon concentrations in ground water were monitored over a period of two years and five months. Monitoring indicated that the contamination levels tended to decrease, although sharp fluctuations were observed. Correlation and spectral analysis were used, among other methods, to construct a model of the hydrocarbon concentrations' evolution. We established the existence of maximum values of cross-correlation between the time series for hydrocarbon content and rainfall, with different lags for each well. Cross correlation is most clear in several wells located along a paleochannel in which the contamination tended to flow. Quantification was therefore possible of both the contaminant propagation rate and the permeability of the aquifer in that area. Although more detailed analysis showed that the high correlation values were due to a single data set (corresponding to the maximum concentrations observed in each well after a period of exceptionally heavy rainfall), the above conclusions may still be considered valid for periods of intense recharge of the aquifer, as demonstrated by an artificial recharge test.     

Effect of sulphur dioxide on precipitation and on the sulphur content and acidity of soils in Alberta,Canada

Rain and snow in Alberta are seldom acid. The S content of snow is so low that the snow pack gives a deposition of less than 1 kg S ha^?1, even downwind from large SO₂ emission sources. Rainfall contributes at the most 4 kg S ha^?1 yearly near SO₂ sources, and only about 1 kg S ha^?1 in clean areas. However, rain intercepted by forest trees exposed to SO₂ emission becomes acid (pH 3.5 to 4.5) and has a S content of 3 to 4 times greater than rain. Soils absorb large amounts of S from emissions (up to 50 kg S ha ^?1 annually) but much of the S is found in non-sulphate form. Soils are slowly acidified by the SO₂ at a rate estimated at 1 pH unit in 10 to 20 yr. Water surfaces will absorb SO₂ emissions at a rate of about 4 to 15 kg S ha^?1 annually. Particulates deposit 3 to 4 times as much S as is deposited by rainfall.     

Studies of precipitation contamination levels over the north-western forests of Russia subject to emissions from the two nickel smelters

The results of investigations carried out in the forests of Kola peninsula subject to long-term air pollution by the nickel industrial enterprises are presented. Samples of rainwater from the open sites, from under the coniferous (pine) trees crowns and of the stemflow were collected at various distances from the emission sources. The highest levels in pollution of rainwater are detected over the area adjacent to the smelters. Researches of contamination of the precipitation in the vicinity of the two nickel enterprises of Kola peninsula show that concentrations of pollutants vary significantly (up to an order of magnitude) depending upon the meteorological conditions. The area of impact on forests of Kola peninsula is restricted by the radius of 30–40 km from the emission sources.     

Injuries in the Iowa Certified Safe Farm Study

The aims of this article are to assess injury characteristics and risk factors in the Iowa Certified Safe Farm (CSF) program and to evaluate the effectiveness of CSF for reducing injuries. This intervention program includes a health screening, on-farm safety review, education, and monetary incentives. Cohorts of farmers in an intervention group (n = 152) and control group (n = 164) in northwestern Iowa were followed for a three-year period. During the follow-up, there were 318 injuries (42/100 person-years), of which 112 (15/100 person-years) required professional medical care. The monetary cost of injuries was $51,764 ($68 per farm per year). There were no differences in the self-reported injury rates and costs between the intervention and control groups. Raising livestock, poor general health, and exposures to dust and gas, noise, chemicals and pesticides, and lifting were among risk factors for injury. Most injuries in this study were related to animals, falls from elevation, slips/trips/falls, being struck by or struck against objects, lifting, and overexertion. Machinery was less prominent than generally reported in the literature. Hurry, fatigue, or stress were mentioned as the primary contributing factor in most injuries. These findings illustrate the need for new interventions to address a multitude of hazards in the farm work environment as well as management and organization of farm work.