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The US Department of Agriculture’s Report and Recommendations on Organic Farming (USDA) cited increasing concern among farmers, environmental groups, and the general public about the adverse effects of the US agricultural production system, particularly the intensive monoculture of cash grains and the extensive and often excessive use of agricultural chemicals, both fertilizers and pesticides. The USDA report found that many farmers had shifted away from conventional farming systems to a less intensive, low-input approach based primarily on sod-based rotations and mixed crop-livestock enterprises. Sustainable farming systems in the United States have developed and continue to perform remarkably well, despite a formidable array of specific policy disincentives and broad institutional and structural constraints. The heightened activity in sustainable agricultural research and education programs within the USDA/land grant community is beginning to address the urgent need for reliable and readily available information on low-input farming technologies and systems.

Santos et al. (2012) address the important issue that 14C dating of the carbon occluded in silica phytoliths (PhytOC) isolated from contemporary plant materials can produce ages that are incompatible, being often several kyr older, with both their known recent origin and the 14C age of the bulk plant material. In their article, Santos et al. (2012) propose that the anomalously old 14C carbon dates of PhytOC from harvested plant materials are based on plants taking up "old" dissolved soil carbon to the plant by roots during nutrient uptake. They then propose that this old soil-derived carbon is subsequently partitioned from the general plant biomass into either the silica phytoliths they produce, or as recalcitrant organic matter elsewhere in the plant. We suggest that the full data available for PhytOC 14C dating does not support this hypothesis. Santos et al. (2012) also address the important issue of contamination of PhytOC by general plant biomass material that can occur with procedures that incompletely extract phytoliths. Whilst we agree that such contamination needs to be avoided when examining the nature of PhytOC, we also point out that the converse problem, i.e. removal of PhytOC by over-vigorous extraction procedures, can also have important adverse consequences.

High-protein wheats (Triticum aestivum L.) are not preferred for Oriental diets. Because the protein content of soft white winter wheat grown extensively in the U.S. Pacific Northwest is often higher than the optimum (100 g kg −1 ) for export, there has been a decline of wheat exports to Japan and other Pacific Rim countries. The present study was undertaken to examine the trends in protein levels during 1979 to 1988 and to evaluate the influence of wheat cultivars and climatic parameters on protein content of SWW wheat in the Pacific North-west. The maximum and minimum temperatures, precipitation, and evaporation during each of 9 wk prior to crop harvest were tested for their effect on protein content [...]

Nitrogen Recovery Efficiencies (NRE) as calculated by the Isotopic dilution technique or the difference method are subject to errors under different conditions. The assumptions underlying these methods and the conditions and factors that must be considered while using these methods have been discussed. Majority of the reports suggest that the difference method gives higher values than the isotopic dilution technique. Results of a pot experiment show the importance of accounting the N held in roots for estimating NRE by either of the methods. Although the isotopic dilution technique has been invariably more precise, it was not necessarily representing the true NRE value. Contrary to some earlier reports, it was observed that Added Nitrogen Interaction (ANI) occurred even in field experiments. Guidelines are provided to assist researchers in assessing the validity of using isotopic or difference method in a given situation. For conditions where the NRE values obtained by either of the methods are influenced by ANI, a method of correcting the NRE values has been suggested, to arrive at the most probable value.

The addition of N fertilizer to soil has been shown to stimulate the uptake of native soil N via a priming effect recently termed added nitrogen interaction (ANI). This ANI, due to pool substitution, can substantially affect the N-recovery efficiency (NRE) by plants as calculated by the ¹⁵N isotopic dilution technique. We evaluated NRE in a pot study using ‘Edwall’ spring wheat (Triticum aestivum L.) with three soils (Palouse, a fine-silty, mixed, mesic Pachic Ultic Haploxeroll; Ritzville, a coarse-silty, mixed, mesic Calciorthidic Haploxeroll; and Shano, a coarse-silty, mixed mesic Xerollic Camborthid) of varying organic C (OC) levels and five levels of ¹⁵N-labeled fertilizer. Data obtained at 60 d after emergence (DAE) showed that NRE generally increased with fertilizer additions, was lowest in the soil having the greatest OC, and ranged from 57 to 79%. The NRE values estimated by the isotopic method averaged 20% lower than those estimated by the difference method, although the two estimates were strongly related. Although the magnitude of ANI showed no direct relationship to OC levels, it was strongly related to N rates, OC, soil C/N ratio, and N lost, which together explained 73% of the relationship. The magnitude of occurrence of ANI appears to be influenced by several factors and thus may be soil specific. Regression of NRE with soil properties showed that NRE was influenced primarily by the same factors that influenced ANI. This study suggests that, for accurate comparisons of nitrogen recovery efficiency between soils or treatments using the isotopic method or for comparing methods of determining N-recovery efficiency, the role of added N interaction must be considered.

A series of experiments were conducted to evaluate the performance of 7- to 21-day-old broilers fed diets in which excesses of essential amino acids (EAA) were minimized. A 23% protein diet in which all EAA except TSAA were in excess was reduced in protein in a stepwise manner, keeping the corn: soybean meal ratio constant, to the point where all EAA were at minimum requirement level based on the 1984 National Research Council (NRC) requirements. Crystalline EAA supplemented those EAA that became deficient as dietary protein was reduced. Other test diets included one containing an additional 10% of the particular EAA in question and one with nonessential amino acids (NEAA) added to make the low-protein diet isonitrogenous with the 23% control. Performance of birds fed the low-protein test diets was not significantly different from that of the control birds. All EAA appeared to be adequate at levels recommended by the NRC in 1984 except Trp, which required .25% for optimal performance. A growth response was observed when Gly was used as the NEAA source; however, no response was noted when mixtures of NEAA were used as the NEAA source, suggesting that Gly may have been limiting in these earlier treatments. Total carcass protein of birds fed the low-protein test diets in which all EAA were minimized was equal to that of the control birds. In a final experiment utilizing the EAA-balanced, low-protein diet, dietary energy was allowed to vary by 15%. The EAA intake was constant, indicating that birds were eating to satisfy EAA requirements rather than energy requirements. Increased carcass fat deposition paralleled dietary energy increases.

Soil degradation reduces soil productivity and is a serious problem on much of the land in semi-arid regions. To avert continued degradation, the soil productivity balance must be shifted from degrading processes to conservation practices. Crop residue management and conservation tillage are on the positive side of the balance. When adequate residues are available and conservation tillage is used, soil erosion is greatly reduced and water conservation is enhanced. Water conservation is important for improving crop yields in semi-arid regions, especially where irrigations is not used. A major constraint to residue management in many countries is low production and widespread use for other purposes. In such cases, clean tillage and appropriate support practices such as contouring, furrow diking, strip cropping and terracing may provide adequate soil and water conservation benefits. Where these are not adequate, alternative management practices should be implemented to ease the demand for residues, thus permitting more of them to be retained on the land for soil and water conservation purposes. Some alternative practices include limited or selective residue removal, substituting high quality forages for residues as animal feed, alley cropping, using wasteland areas more effectively, improving the balance between feed supplies and animal populations, and using alternative fuel sources.

An important conclusion of the recent International Conference on Dryland Farming was that dryland agriculture must play an increasingly important role in meeting future world needs for food and fiber (International Conference on Dryland Farming, Executive Summary, 1989). Improvements in crop and livestock production in the dryland regions is constrained not only by the limited supply of available water but also by the low and declining soil productivity. As a result of improper soil management and overgrazing, the soils in many areas have been severely degraded by wind and water erosion and loss of soil organic matter. Water conservation must be regarded as the essential first step in improving the production capability of these lands whether the soils have been degraded or not. Little can be gained from various technological inputs such as fertilizers, improved crop varieties, pesticides, and better sowing methods unless the available water supply is maximized for crop production.

Arid and semiarid regions comprise almost 40% of the world’s land area and are inhabited by some 700 million people. Approximately 60% of these drylands are in developing countries. Low rainfall areas constitute from 75–100% of the land area in more than 20 countries in the Near East, Africa, and Asia. Farmers in these regions produce more than 50% of the groundnuts, 80% of the pearl millet, 90% of the chickpeas, and 95% of the pigeon peas. These dryland areas will continue to produce most of the world’s food grains for expanding populations in the years ahead. However, yields are extremely low compared with those of the humid and subhumid regions. In some countries of sub-Saharan Africa and the Near East food grain production per capita has declined significantly during the past decade. Although part of this decline can be attributed to high rates of population growth, periodic drought, and unfavorable agricultural production and marketing policies of the national governments, much of it results from the steady and continuing degradation of agricultural lands from soil erosion and nutrient depletion and the subsequent loss of soil productivity (FAO, 1986; Dregne, 1989).

Laboratory incubation studies were conducted to determine the rate and extent of decomposition of sewage sludge compost in soil. Freeze-dried compost made from undigested sewage sludge was mixed with three soils (a loamy sand, a silt loam, and a silty clay) and a sand at rates of 0, 2, 4, and 6% of the dry weight. The mixtures were incubated at 22C in a constant atmosphere of CO₂- and NH₃-free air. Rates of mineralization and decomposition were determined by monitoring CO₂ and NH₃ evolution and changes in the organic and inorganic fractions of C and N with time. Cumulative CO₂ evolution was linearly related to the rate of sludge compost applied. Approximately 16% of the compost C evolved in 54 days of incubation. Nitrogen mineralization was lowest in the silt loam-compost treatment. In the sand-compost mixture, mineral N was immobilized during incubation. Ammonia volatilization from all of the treatments was minimal. Approximately 6% of the compost N in the loamy sand-compost treatment had mineralized after 54 days incubation. Interlattice fixation of NH₄⁺ may have occurred in the silt loam and silty clay soils.

A laboratory incubation study was conducted to determine the rate and extent of decomposition of sewage sludge compost in soil amended with compost fractions of various particle sizes. Cured compost was passed through a 6-mm screen and further fractionated with a 1-mm sieve. The three fractions of compost (

Aspergillus fumigatus, a medically important fungal opportunist and respiratory allergen, was isolated from woodchips and sewage sludge used in the production of compost at the U.S. Department of Agriculture's composting research facility in Beltsville, Md. It was also regularly isolated as a dominant fungus during forced aeration composting and after 30 days in an unaerated stationary curing pile; in both cases, the fungus was found in pile zones with temperatures less than 60 degrees C. Compost stored outdoors in stationary unaerated piles from 1 to 4 months after screening out of woodchips contained easily detectable amounts of A. fumigatus in the exterior pile zones (0- to 25-cm depths). Semiquantitative studies of the airspora at the composting site revealed that A. fumigatus constituted 75% of the total viable mycoflora captured. At locations 320 m to 8 km from the compost site, the fungus constituted only 2% of the total viable mycoflora in the air. Of 21 samples of commercially available potting soil, one had levels of A. fumigatus nearly equivalent to those of 1-month-old storage compost; 15 others had lower but detectable levels.

Proper management of organic wastes such as crop residues, animal manures, and sewage sludges on land is essential for protecting agricultural soils from wind and water erosion, and for preventing nutrient losses through runoff. Efficient and effective use of these materials also provides one of the best means we have for maintaining soil productivity2 by recycling plant nutrients and by improving soil physical properties. The beneficial effects of organic wastes on soil physical properties are widely known (1, 21) as evidenced by increased water infiltration, water-holding capacity, water content, aeration and permeability, soil aggregation and rooting depth, by decreased soil crusting and runoff, and by lower bulk density.

(1986). Recycling of Organic Wastes for a Sustainable Agriculture. Biological Agriculture & Horticulture: Vol. 3, No. 2-3, pp. 115-130.

Laboratory incubation studies were conducted in which sewage sludge compost was mixed with three soils (Evesboro loamy sand, Christiana silty clay loam, and Fauquier silt loam) and a sand at rates of 0, 2, 4, and 6% (0, 44.8, 89.6, and 134.4 metric tons/ha, respectively) of the dry weight. The mixtures were incubated at 22°C under a flow of CO₂- and NH₃- free air. Extractable P in the compost-sand mixtures ranged from 48 to 81% of the total P. The Evesboro-compost-sand mixtures showed an initial net P mineralization trend followed by a slight immobilization trend at 54 days. The Christiana-compost mixtures had less extractable P than the Evesboro-compost mixtures, but did show initial increase in extractable P followed by a decrease during incubation. The iron and aluminum components in the Christiana soil were probably responsible for net immobilization of extractable P. The Fauquier-compost mixtures had the least extractable P and the highest free iron oxide content. Contrary to the other soils, the Fauquier-compost mixture showed initial net immobilization of extractable P followed by mineralization at 54 days. Ammonium acetate extractable S in the sand-compost mixtures was 8 to 11% of the total S. In the Evesboro-compost mixtures extractable S increased after 54 days incubation. The Christiana-compost mixtures immobilized extractable S early in the incubation but net mineralization of S was subsequently evident where the soil was amended with 4 and 6% compost. The Fauquier-compost mixture had the least extractable S and had immobilization-mineralization trends similar to the extractable P data. Both extractable P and S are in sufficient quantities at the 44.8 metric tons/ha application rate to sustain plant growth and, therefore, sewage sludge compost could be used to correct P or S deficiencies in most soils.

Fertilizer nitrogen is subject to loss from the soil-root zone, and immobilization by the soil and rhizosphere microfloras, which can result in low recovery and use efficiency of the applied nitrogen. With increasing rates of application, fertilizer nitrogen efficiency decreases progressively, while leaving an increasing amount of unused nitrogen as a potential pollution hazard. Since the point of greatest economic return from this nutrient is usually somewhere below the point of maximum yield, it should be possible to adjust fertilizer nitrogen rates for maximum return and minimum loss to the environment. This can be achieved through improved soil and crop management practices, including proper timing of application of conventional nitrogen fertilizers and use of deep-rooted crops for recovery of leached nitrate. A rational approach to more meaningful nitrogen recommendations is needed, one which would account for residual fertilizer nitrogen and mineralizable soil nitrogen, and allow an accurate prediction of the amount of supplemental fertilizer nitrogen necessary to produce the desired yield. Efficiency of fertilizer nitrogen might also be increased with controlled release fertilizers, including the use of coated granules, and compounds of limited water solubility blended with conventional nitrogen fertilizers, to achieve a specific release rate coincident with the nitrogen requirements of a crop. Formulation of ammoniacal fertilizers with nitrification inhibitors offers considerable opportunity for increasing fertilizer nitrogen efficiency.

Many different types of surfactants are employed by biological investigators to reduce the surface tension of aqueous solutions in order to enhance the wetting of tissues for the penetration of various test compounds. Surfactants are frequently used at concentrations that greatly exceed the amount required for a maximum reduction of surface tension and with little consideration of the fact that they are chemicals of wide diversity with the potential of exerting biochemical effects upon growth and metabolic processes of living organisms. This may not be of concern where the objective is to enhance the penetration of herbicides, defoliants, or insecticides; but in other circumstances involving complex growth phenomena, such as differentiation, induction, or auxin-mediated events, greater caution is suggested in the use of surfactants.

@,in was surface applied at a rate of 782 glplot to 3 15.2asrn plots L10 ppm based on a 2 X lo6 Ib wril/aue 15.2 cm :iph,]]. Immediately after application. 1 of 3 soil water re(flooded, moist, nonflwdedl was imposed on each plot. An ling system was used to measure the atmospheric con&?:" gradient of dieldrin between 10 and 30 cm above each &lollations based on the aerodynamic method indicated z:lppmximately 18% of the applied dieldrin volatilized from the in 5 months. whereas only 2 and 7% volatilized from &d,and nonflooded plots, respedvely. Multiple regression dl indicated that of the climatic variables measured, temperathe greaten effect on dieldrin volatilization. There was no c"nt dieldrin degradation in any of the plots.

The effectiveness of potassium azide (KN₃) as a nitrification inhibitor for field-applied anhydrous NH₃ was evaluated on a Naff silt loam in the winter wheat (Triticum aestivum L.) area of eastern Washington. Formulations of KN₃ in liquid NH₃ of 0, 2, and 6% (w/w) were applied to fallow soil in August 1969 at a rate of 112 kg N/ha (81-cm spacing) with a special field applicator. The 2% formulation was also applied at a rate of 224 kg N/ha. The NH₃ retention zone was sampled periodically through February 1970 and analyzed for NH₄⁺-N, NO₂⁻-N, and NO₃⁻-N. Both levels of KN₃ were effective in reducing the nitrification rate during the early post injection period, but the higher level was more effective at later dates. Two months after application, the amounts of NO₃⁻-N recovered from the retention zone as percent of total extractable N were 67, 48, and 36 for NH₃ alone, NH₃ + KN₃ (2%), and NH₃ + KN₃ (6%), respectively. Percentage amounts of NO₃⁻-N decreased with increase in N application rate. Nitrification inhibition due to KN₃ was still evident 6 months after application, particularly at the high N rate. The inhibitory effect of low soil temperature during the winter months was also apparent. These results indicate that KN₃ formulated with anhydrous NH₃ was an effective nitrification inhibitor for this N source.

Surfactants are frequently employed by biological investigators to reduce the surface tension of aqueous solutions and to bring about ready wetting of tissues. Maximum expression of this property is attained at low surfactant concentrations, though the effective concentration varies somewhat between preparations. In some situations the role of the surfactant is that of a solubility aid or stabilizer of a 2-phase system, in which case higher concentrations may be necesssary. In the investigations reported here we confined our attention to nonionic surfactants, on the assumption that they would be less likely to be retained by plant tissues than cationic or anionic compounds. Our primary interest was with effects on root growth and function. Materials and Methods

In the investigation of NO 3 − uptake by excised roots, pH of salt solutions can be effectively controlled by periodic additions of a cation exchange resin, Amberlite IR-120, in the H+ form. This method of pH control provides for the addition of H+ to systems without an accompanying anion which might influence the absorption of NO 3 − . The resin appeared to provide a favorable buffering capacity during an extended period and the method was especially useful for NO 3 − uptake studies conducted at high root-to-solution ratios.

Drying patterns in soil caused by a more rapid rate of water evaporation from the retention zone after NH3 injection are described. Quantitative data from pot and field observations show the development of moisture gradients inclined toward the center of the retention zone from the periphery, after different incubation times and periods of exposure. These patterns tended to persist over a period of several months even when pots of soil were subjected to alternate wetting and drying. A number of explanations for these NH3-induced drying patterns are considered and their possible agronomic significance is discussed.

Laboratory experiments were conducted to determine the rate of decomposition of wheat straw added to soil when continuous aeration was conducted with N₂-O₂ gas mixtures containing 0, 0.5, 1.0, 2.5, 5.0, and 21% oxygen at flow rates of ⅛, ¼, ½, 1, and 2 liters per hour. Rates of decomposition and total decomposition were followed by determination of wheat straw carbon evolved as CO₂. Total decomposition at all oxygen levels varied directly with aeration flow rate, except for the 0% level where an inverse relationship was observed. Microbial activity at the 21% oxygen level was greatly stimulated as flow rate increased from ⅛ through 2 liters per hour. A rapid increase in microbial activity occurred for the 0.5, 1.0, 2.5, and 5.0% oxygen levels as flow rate increased from ⅛ through ½ liters per hour, however, little increase in CO₂ production was observed at higher flow rates.