C and N accumulation in arable soils of West Germany and its influence on the environment — Developments 1970 to 1998

During the last three decades, large amounts of soil organic matter (SOM) and associated nutrients have been accumulated in arable soils of Western Germany (former FRG) due to deepening of the plough layers (from < 25 to > 35 cm) and to fertilizer application rates which have exceeded the amounts of nutrients removed in harvested crops. Organic carbon and total nitrogen balances (1970—1998) on 120 plots from 16 farms in southern Lower Saxony yielded a cumulative increase of up to 16 t C ha⁻¹ and 1 t N ha⁻¹ in loess soils used for cash crop production and up to 26 t C ha⁻¹ and 2.4 t N ha⁻¹ in sandy soils under livestock production. The buffering capacity for reactive compounds, particularly of C, N, S and P and of other (organic or inorganic) pollutants will reach its limits in the near future, after organic matter ”︁equilibria” have been re‐established. An immediate adaptation of the current fertilizer application rates to the nutrient export by field crops is therefore urgently needed.     

A quick‐test procedure for soil and plant tissue nitrates using test strips and a hand‐held reflectometer

Abstract

Development of a nitrate quick‐test for use by fanners or field consultants would likely encourage the use of plant tissue and soil nitrate tests as a means to improve nitrogen management. To evaluate a quick‐test method, nitrate concentrations in plant tissue and soils were measured using commercially available nitrate test strips and a hand‐held reflectometer. The results were compared with those obtained with standard laboratory methods. Test strip accuracy and precision and reflectometer precision were determined over a 10 day period using standard KNO₃solutions and colored paper strips. Coefficients of variation ranged from 22.4 to 9.5 percent for the test strips and from 3.5 to 1.6 percent for the reflectometer. Quick‐test results were highly correlated with laboratory results for both plant tissue nitrate (r=0.87) and soil nitrate (r=0.98) concentrations. Results indicated that test strips provide a rapid, reasonably accurate and precise method to determine nitrate concentrations in both soil and plant material     

Growth,Oil Yield,and Ion Partitioning in Basil Grown on Sodic Soils

Abstract

A field experiment was conducted on sodic soil during its rainy seasons of 2004 and 2005 to evaluate five germplasms of Ocimum basilicum (viz. CSLT 5, CSLT 9, CSLT‐12, CSLT‐12‐1, and CSLT‐13) for their growth performance, their oil yield, chemical constituents of their oil, and ion‐partitioning characteristics in different parts of the plants. The highest shoot yield was recorded in CSLT‐12, followed by CSLT‐9 and CSLT‐13. The highest oil yield was recorded in CSLT‐13, followed by CSLT‐12‐1. This indicated that a high herbage yield does not always result in a high oil yield. Germplasm CSLT‐12 and CSLT‐12‐1 seemed to have better adaptation in sodic soil then other germplasms on the basis of root architecture and root density. Germplasm CSLT‐5 was of the linalool chemotype, yielding 62.36% linalool in oil, whereas CSLT‐13 and CSLT‐9 were methyl chavicol chemotypes, yielding 69.59% and 56.98% of methyl chavicol, respectively. Germplasms CSLT 12 and CSLT 12‐1 are intermediate types that yielded 48.86% of methyl chavicol and 43.37% of linalool. The root, stem (main branch), and laterals (primary branches) were better sodium (Na)+accumulators then leaves and inflorescences. On the other hand, leaves were better chloride (Cl^?) accumulators than roots. A higher K⁺/Na⁺ ratio was found in the immature leaves than in the matured leaves.     

A comparative evaluation of the Mississippi soil test method for determining available manganese,magnesium, and calcium

Abstract

Soil Samples (72) were collected from the Delta, Hill, and Northeast Blackland areas of Mississippi. Chemical analyses for manganese, magnesium, and calcium were made using the Mississippi Soil Test Solution (MSTS) and several other extracting solutions chosen for comparison. For the determination of available soil manganese, the MSTS proved to be as effective as either the Double Acid (0.025 N HCl in 0.05 N H₂SO₄) or 0.1 N H₃PO₄. The acid extractants removed more manganese than 1 N NH₄OAc (pH 7.0) and therefore included forms that are not exchangeable. The methods studied for magnesium determinations were equilibrium extraction with 1 N NH₄OAc, MSTS, Double Acid, 0.25 N CaCl₂, and leaching with 1 N NH₄OAc. All methods were highly correlated and therefore would be equally effective in determining available soil magnesium. Since MSTS and equilibrium extraction with 1 N NH₄OAc removed similar amounts of magnesium from the soil, the same calibration can be used. Calcium determinations were made using equilibrium extraction with 1 N NH₄OAc, MSTS, and Double Acid, and by leaching with 1 N NH₄OAc. All methods proved effective in measuring available soil calcium on acid soils.     

水保林体系的整体增益

水保林体系的整体增益张淑芝，孙尚海（甘肃省平凉地区水保科研所，平凉市７４４６００）ＩｎｔｅｇｒａｌＢｅｎｅｆｉｔｏｆＦｏｒｅｓｔＳｙｓｔｅｍｆｏｒＳｏｌｌａｎｄＷａｔｅｒＣｏｎｓｅｒｖａｔｉｏｎ￥ＺｈａｎｇＳｈｕｚｈｉｅｔａｌ．（ＰｉｎｇｌｉａｎｇＳ...     

Effects of agricultural practices on the hydrodynamics of a deep tilled hardened volcanic ash–soil (Cangahua) in Ecuador

The rehabilitation of indurate pyroclastic formations of the Ecuadorian Sierra (cangahua) paves the way for the development of new agricultural areas. The material derived from the fragmentation of the hardened volcanic ashes is strongly prone to pluvial erosion, essentially because it has a fine silty–sandy texture, and because contains no organic matter and no clay minerals. Rainfall simulation was implemented before and after three cycles of cultivation to asses the evolution of soil structure and its susceptibility to erosion. The cultivated plots were < 1% slope and the rainfall simulation tests were conducted after the harvest on bare surfaces. Two soil preparations, (coarse and fine) and four different agricultural practices, (organic matter, green manure, mineral fertilization, and zero fertilization) were evaluated; as well reference/control plots (uncultivated bare plots).