Rainfall and previous crop effects on crop yields
Afield study was conducted between 1972 and 1982 to compare the effects of previous crop on row crop yields under rainfed conditions in eastern Nebraska. The objectives were to determine the effects of fallow and three previous crops: corn (Lea. maysLJ, soybeans /Glycine max (L.) Mem], and grain sorghum /Sorghum bicolor (L.) Moench], on the growth and grain yield of the same crops. The study was conducted on a Sharpsburg silty clay loam (fine, montmorillonitic, mesicf Typic Argiudoll). Corn grain yield was most variable (C. V. 23.4percent) compared to soybean (C. V. 13.6percent) or grain sorghum (C. V. 9.5 percent) yields. Corn was also the most sensitive crop to previous crop effects. The range of treatment yields for each crop was 47 percent, 22 percent, and 11 percent of the overall means for corn, soybean, and sorghum, respectively. Previous crop affected yields for all crops, but the effects were not consistent across years. All crops produced highest yield following fallow. Yields of corn, soybean, and grain sorghum following fallow were 74, 25, and 10 percent higher than their respective monoculture yields. In years of average precipitation, a corn-soybean sequence produced the greatest yield. In years having above- or below-normal precipitation, a grain sorghum-soybean sequence produced the highest yield.
Nitrogen Management and Interseeding Effects on Irrigated Corn and Sorghum and on Soil Strength1
A 15-yr experiment on Sharpsburg silty clay loam (fine, montmorillonitic, mesic Typic Argiudolls) investigated N management effects on corn (Zea mays L.) and grain sorghum [Sorghum bicolor (L.) Moench] grown side by side, under identical furrow-irrigated conditions. Included were comparisons of anhydrous ammonia (AA) and N solution (UAN) as N sources, planting time (UAN-PL) vs. summer sidedressing (UAN-SD) application of the N, and rates of 90,180, and 270 kg N ha-'. Additionally, interseeding of rye (Secale cereale L.) into high N plots and alfalfa (Medicago sativa L.) into check plots of corn was accomplished at the time of ridging for furrow irrigation. The objectives were to evaluate the long term effects of varied management of the two N carriers and the interseedings on grain yields and N utilization, and the relative effects of these treatments on soil strength. Grain sorghum was the more productive crop under conditions of low N availability while corn responded to higher N rates, becoming the more economic crop with yields approaching 10 Mg ha-l when N was plentiful. Yield increases averaged 5% greater for UAN-SD over UAN-PL, and AA was slightly more effective than UAN-SD for both crops. Interseeded alfalfa and rye green manures provided average corn yield increases of 880 and 585 kg ha-@, respectively, explainable in part by improved N economy. No significant differences in penetrometer or vane shear tests were found between soils from AA and UAN-SD plots, although there was a tendency toward lower soil-strength values with both N carriers, relative to check plots. RTILIZER N has contributed more toward increasE ing yields of grain crops in the U.S. and the world in the past 30 years, than any other single factor. At the same time N has become the foremost input in relation to cost and energy requirement in advanced agricultural production systems. The national growth in its use to the current approximate 11 million tons annual N consumption, far exceeding N inputs prior to the Chemical Age in agriculture, has added the further dimensions of excessive N for crops and of groundwater pollution with nitrate (5,7,14,25). Accordingly, it is in the best interests of the farmer, fertilizer dealer, and manufacturer that fertilizer N be used in the most efficient way possible for minimizing costs of crop production, conserving energy, and preserving environmental integrity. Many short-term studies have demonstrated the need for adjusting N rate to the yield obtainable, and even more importantly, to the amount of residual mineral N in the soil rooting zone at planting and the soil's nitrification capacity (1 0,16,17,22). Imgation, where practiced, is recognized as a primary vehicle for carrying NO; to groundwater, therewith necessitating the integration of water and N management practices for
Instrumentation and Automated Photometric Titration Procedure for Total Acidity Determination in Red Wine Employing a Multicommuted Flow System
An automated procedure for photometric titration of red wine and associated instrumentation is described. The procedure was based on the flow-batch approach implemented employing multicommutation. The photometric detection was carried out using a homemade LED-based photometer. The mixing device, LED, and photodetector were attached to the titration chamber in order to form a compact and small-sized unit. The flow system comprised an automatic injector and three-way solenoid valves, which were controlled by a microcomputer through an electronic interface card. The software, written in Quick BASIC 4.5, was designed with abilities to accomplish all steps of the titration procedure including data acquisition and real-time processing to decide about the course of titration in the following step and so forth, until the titration endpoint was reached. The usefulness of the proposed titration system was demonstrated by analyzing red wine samples. When results were compared with those obtained using the AOAC reference method, no significant difference was observed at the 95% confidence level. A relative standard deviation of ca  2% (n=9 ) was obtained when processing a typical red wine sample containing 7.3 gl -1 total acidity expressed as tartaric acid.