Nitrate leaching under furrow irrigation as affected by crop sequence and tillage

The potential for NO3-N leaching after alfalfa (Medicago saliva L.) in irrigated crop production depends on cropping sequence and tillage practices. A 2-yr field experiment in south-central Idaho compared the NO3-N leached following alfalfa of a conventional tillage bean-bean (Phaseolus vulgaris L.) rotation with a silage corn (Zea mays L.)-winter wheat (Triticum aestivum L.) rotation in a conventional tillage or no-till system. Nitrate leaching was determined by: (i) sampling the soil solution below the root zone (1.2 and 1.5 m) using ceramic-tipped samplers and calculating the N movement from the water balance, and (ii) measuring the change in soil NO3-N at 1.35 to 4.5 m from soil samples taken in the fall and spring to 4.5 m. During the second growing season, average soil solution NO3-N concentrations (below the root zone) were 28, 4, and 10 mg L-1 for the bean-bean, corn-wheat no-till, and corn-wheat tilled treatments, respectively. The soil NO3-N in 1.35 to 3.3 m at the end of the study was 80 kg N ha-1 higher for the bean-bean treatment than for the corn-wheat treatments. The NO3-N that moved below 1.35 m during the 2 yr was 53 kg ha-1 higher for the bean-bean than for the corn-wheat treatments. The soil NO3-N in the 1.35 to 3.3 m depth after 2 yr was 21 kg ha-1 higher for the corn-wheat under conventional tillage than under the no-till system

Controlling nitrate leaching and erosion on irrigated land

New integrated agronomic cropping systems that nearly eliminate irrigation-induced erosion, significantly reduce nitrate leaching potential, increase crop utilization of nitrogen from legume sources and fertilizer, improve irrigation uniformity, decrease production costs, and increase net profits have resulted from several years of research at Kimberly, Idaho. These systems include growing corn or cereal without tillage following alfalfa to efficiently utilize nitrogen from the legume and reduce irrigation-induced erosion. Where no corn was grown following alfalfa, nitrate-N accumulated up to 550 lbs/ac in the upper 5 feet of soil compared to only 50 lbs/ac where corn was grown. Where beans were grown for two seasons following alfalfa, nitrate-N leaching was 50 lbs/ac more than where corn and then winter wheat were grown. Banding nitrogen fertilizer on the opposite side of the corn row from the irrigation furrow used all season reduced nitrate leaching as compared to where a furrow was irrigated on the same side of the row as the fertilizer band. Nitrate moves below the root zone during wet winters by deep drainage and pass through flow. Polyacrylamide (PAM) concentrations of 10 ppm or less applied into the irrigation water can almost eliminate furrow erosion, and it increases infiltration. Applying cheese whey alone and in combination with straw at whey rates of 12 gallons and straw rates of 4 lbs/100 ft of row before beginning irrigations reduced sediment loss by more than 95%

Early carboniferous brachiopod faunas from the Baoshan block, west Yunnan, southwest China

38 brachiopod species in 27 genera and subgenera are described from the Yudong Formation in the Shidian-Baoshan area, west Yunnan, southwest China. New taxa include two new subgenera: Unispirifer (Septimispirifer) and Brachythyrina (Longathyrina), and seven new species: Eomarginifera yunnanensis, Marginatia cylindrica, Unispirifer (Unispirifer) xiangshanensis, Unispirifer (Septimispirifer) wafangjieensis, Brachythyrina (Brachythyrina) transversa, Brachythyrina (Longathyrina) baoshanensis, and Girtyella wafangjieensis. Based on the described material and constraints from associated coral and conodont faunas, the age of the brachiopod fauna from the Yudon Formation is considered late Tournaisian (Early Carboniferous), with a possibility extending into earlyViseacutean.<br /

Computer Methods in Structural Analysis

503 hlm, Ilust, 21 c

RECENT EXPERIENCE WITH NUMERICAL ANALYSIS OF MINING ENGINEERING RELATED PROBLEMS.

The paper sets out the numerical techniques currently being applied to stress analysis problems associated with the large hard-rock mining operation at Mount Isa. This clearly shows the apparent ascendence of boundary element techniques over existing finite element methods and leads to the conclusion that a combination of the methods has best promise for handling the large-scale non-linear material analyses that are encountered

Boundary element modelling: Near surface excavations

The present paper has adopted the Mindlin solution for the plane strain case and then applied this to use a two-dimensional boundary element formulation using direct integration for a constant stress element. The results are compared with those of the Kelvin solution to the same problem using the same element approximation. The paper highlights the usefulness of the Mindlin solution for this class of problem