Cropping systems effects on snowmelt losses of solids and associated organic carbon

Increase in alfalfa (Medicago sativa L.) production for energy (gasification of stems) and protein supplement (from leaves) has been proposed for the upper Midwestern United States, an area where corn (Zea mays L.) in rotation with soybean (Glycine max L.) is the predominant crop sequence. This study was undertaken to assess the impact on runoff and water quality, especially for the loss of oxygen demanding material with snowmelt. Four field size watersheds were instrumented at Morris, Minnesota, USA on a rolling prairie landscape. Snowmelt runoff from each watershed was measured with two flumes with overlapping ranges arranged in series. An automatic water sampler collected runoff samples for chemical analysis. Oxygen demand was used as a surrogate for reduced carbon. Water samples were analyzed for total solids, biochemical oxygen demand (BOD), and chemical oxygen demand (COD). Based on the results of snowmelt events of 1997, 1998, and 1999, the alfalfa fields yielded more runoff than corn-soybean fields. The loss of total solids was more consistent from alfalfa fields. Total solids losses interacted with crop and year. Compared to alfalfa fields losses were less following soybeans and greater following corn. On average losses were similar between alfalfa and corn-soybean fields. Runoff from alfalfa fields contained about four times more BOD than corn-soybean fields. Although not statistically significant due to only two replications, there was a similar trend for COD. This study shows that although losses of total solids in snowmelt from alfalfa fields was similar to corn-soybean fields, there can be increased losses of oxygen demanding materials.     

Soil microbial activity,aggregation and nutrient responses to straw pulping liquor in corn cropping

The cereal and grass seed cropping systems of the Pacific northwestern USA generate a valuable fiber source for papermaking. Pulping straw with KOH produces black liquor, an organic waste effluent with potential as a K source and soil amendment. The objectives of this study were to determine if black liquor from wheat straw pulping with KOH improves soil quality including soil aggregation, microbial biomass and microbial activity, and corn yield. A 2-year field trial with a randomized complete block design was conducted with black liquor or KCl applied at 168 and 336 kg K ha⁻¹ at two sites, respectively, planted to corn in Central Washington. Black liquor applied at rates of 168 and 336 kg K ha⁻¹ slightly increased soil pH by 0.2 to 1.4 units and electrical conductivity by 0.0 to 0.8 dS m⁻¹ at both sites, and significantly increased soil test K compared to the nonamended control by 199 to 368 mg K kg⁻¹ soil in the top 5 cm at Paterson and by 44 to 200 mg K kg⁻¹ soil in the top 5 cm at Prosser. Corn had no yield response to the application of either K sources, black liquor, or KCl applied at both rates at both sites. Generally, black liquor applied at these rates increased soil dehydrogenase, β-glucosidase, and arylsulfatase activities, microbial biomass C, and soil wet stable macroaggregates in the top 5-cm soil at both sites. The results of this study suggest that the organic-rich waste liquor from wheat straw pulping with KOH may improve soil quality and soil test K without reducing crop productivity.     

Effects of nitrogen application frequency via subsurface drip irrigation on corn development and grain yield

Subsurface drip irrigation (SDI) has not only potential for water conservation, but also for improving nutrient use efficiency. Two nitrogen (N) application frequencies (every week versus every two weeks, via SDI) were compared in 2012 and 2013 on a Cozad silt loam in North Platte, Nebraska. The weekly treatment was fertigated every week for seven weeks in a row; the bi-weekly treatment was fertigated in weeks 1, 3, 5 and 7. Both treatments received the same total amount of N. There was a positive grain yield response to N application, but no advantage was found to a greater frequency of N application. Corn (Zea mays L.) grain yields and other indicators of corn growth and development (canopy-intercepted light, vegetation indices, indicators of chlorophyll content of corn plant leaves) were not affected by N application frequency.     

(Micro)biological, chemical and physical properties of soils subjected to conventional or no-till management: an assessment of their quality status

In order to evaluate the impact of no-tillage (NT) against conventional-tillage (CT), or the effect of different fertilizers and herbicides, soils recently incorporated to agriculture from the El Salado basin river (Buenos Aires, Argentina) under a corn (1996/1998)-pasture (1998-)rotation were monitored for several soil (micro)biological, physical and chemical properties during the second (1997) to fourth (1999) years from the beginning of the experiment (1996). The rates of exchange of O₂ and CO₂ expressed in terms of kg O₂ or CO₂–C per hectare per day, are denoted as qO₂ and qCO₂. They decreased at the end of the corn growth cycle (T2) along with an increase of the respiratory quotient (RQ=qCO₂/qO₂), when compared to the time of land preparation (T0), irrespective of the management system. Both, qO₂ and qCO₂, increased 8 months after the mixed-grass-legume pasture planting (T3) keeping similar RQs with values slightly higher for NT than CT. At T4 (after 20 months of pasture), a 22 and 21% decrease of organic carbon was registered for NT and CT, respectively, with respect to the beginning of the experiment. A 22% (not significative) and a significative 31% diminish of total nitrogen was observed in the NT and CT systems, respectively. The results obtained are discussed in terms of soil function and sustainability in both management systems tested.     

淀粉凝胶与植物组织培养II.玉米淀粉凝胶培养基对苹果砧木组培生根诱导的同步化作用

珠美海棠和M26苹果矮化砧木分别在琼脂培养基和玉米淀粉（corn starch）凝胶培养基上进行生根培养，结果玉米淀粉培养基不但提高了两种植物的生根率，而且对生根诱导具有同步化效应。珠美海棠生根苗游离氨基酸含量的高效液相色谱（HPLC）分析表明，琼脂生根培养基上，吲哚丁酸（IBA）诱导了天冬氨酸、谷氨酸、组氨酸、苏氨酸、色、蛋氨酸和谷氨酰胺、丙、酪氨酸的降低，但却提高了精氨酸、缬氨酸、苯丙氨酸、亮氨酸和鸟氨酸的含量。当玉米淀粉替代琼脂后，玉米淀粉培养基不但进一步促进了上述氨基酸含量的降低，而且抑制了精氨酸、缬氨酸、苯丙氨酸等的升高。     

Tillage effect on nutrient stratification in narrow- and wide-row cropping systems

Recent research has indicated that conservation systems with narrow-rows have potential for higher crop productivity on southeastern USA Coastal Plains Soil. The objective of this study was to determine how surface tillage and subsoiling affect nutrient distribution in the soil profile in narrow- and wide-row systems. A secondary objective was to determine the effect of row position on soil pH and nutrient concentrations in the wide-row system. Soil samples were collected in 1996 from plots that had been growing soybean (Glycine max (L.) Merr.) double cropped with wheat (Tritiucum aestivum L.) for 3 years and then again in 1999 after 3 years of continuous corn (Zea mays L.). Narrow-row spacing was 19 cm for soybean and 38 cm for corn. Wide-row spacing was 76 cm for both soybean and corn. Wheat was grown in 19 cm wide-rows. Soil samples were randomly collected from throughout the plots in the narrow-row culture. In the wide-row culture, separate samples were collected from the row and from between rows. Treatments were surface tillage (disc tillage (DT) and no surface tillage (NT)), with different frequencies of subsoiling. The soil type was Goldsboro loamy sand (fine-loamy, siliceous, thermic, Aquic Kandiudult). Soil samples from four depths (the surface 5 cm of the A horizon, the remainder of the A horizon, the E horizon, and the top 7.5 cm of the B horizon) were analyzed for pH, P, K, Ca, and Mg. Nutrient concentrations and pH differed little between row spacings at any depth after either 3 or 6 years. Differences due to subsoiling appeared mainly due to nutrient removal as the treatments with more intense subsoiling had higher yield and lower concentrations of nutrients (except K). Concentrations of P, Mg, and Ca at the soil surface tended to be higher in NT than in DT, especially in the mid-rows of the 76 cm wide-row systems. The data suggest only small differences in soil nutrient stratification can be expected as growers adopt narrow-row crop production systems with intensive subsoiling.     

超声波处理玉米磷酸酯淀粉膜液对膜性能的影响

对玉米磷酸酯淀粉基可食膜液进行超声波处理,并对所成膜的抗拉强度、断裂伸长率、透氧率及膜表面微观结构进行了分析。结果表明:超声波处理使膜的抗拉强度、断裂伸长率及阻氧性能提高,膜面均一性也有了一定的改善。在试验范围内,当超声波功率为80W时,对膜液处理50min,膜的性能较佳:抗拉强度为25.53MPa,断裂伸长率为29.07%,透氧率为5.8×10-6cm3/(m2.d.Pa)。     

利用玉米淀粉生产耐水性无臭胶粘剂的研究

用二元酸与玉米淀粉进行酯化反应，形成半酯化玉米淀粉悬浮液，加入水溶性高聚物作为稳定剂，制成玉米淀粉胶粘剂主剂，调胶时加入工业面粉和异氰酸酯化合物，制得实用玉米淀粉无臭胶粘剂。研究结果表明，用该胶压制的胶合板，符合ＧＢ９８４６.１～１２－８８Ⅱ类胶合板指标要求，并且彻底解决了甲醛公害问题.     

玉米自交系杂交当代母本籽粒百粒重变化的研究

通过2003～2004年两年的试验，初步进行了玉米自交系杂交当代母本籽粒百粒重变化的分析研究。结果表明，多数组合杂交当代的母本籽粒的百粒重高于自交。