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The pulp and paper industry in the southeastern USA produces 6500 t of boiler ash and lime by-products (waste lime, grit, and dregs) daily. A survey of 88 pulp and paper mills indicated that most of these by-products are placed in landfills, with only 10% being land-applied. Seventeen boiler ash samples and 14 lime by-products from 12 Alabama pulp and paper mills were analyzed and evaluated for their potential as soil liming materials. Most boiler ash resulted from the burning of wood or wood in combination with other materials and averaged 37% calcium carbonate equivalent (CCE), while 14 lime by-products averaged 99% CCE. In an 84-d incubation study, boiler ash and lime by-products applied to an acid (pH = 5.2) Marvyn loamy sand (fine-loamy, siliceous, thermic, Typic Kanhapludults) at equivalent rates based on CCE resulted in mean pH values significantly higher than values achieved with agricultural lime. All materials increased Mehlich-1 extractable P, K, and Mg. In a field study conducted on an acid (pH = 5.1) Vaiden clay (very-fine, montmorillonitic, thermic Vertic Hapludalfs), dallisgrass-fescue (Paspalum dilatatum Poir.-Festuca arundinacea Schreb.) herbage yield increased 62% the second year and 49% the third year after surface application of boiler ash, lime by-products, and agricultural lime.

SUMMARY Land application of paper mill SC significantly in-creased corn yields even in the absence of mineral fer-tilizer. Leaf total N measurements indicated that moreN was available for uptake by the corn plants duringthe growing season where SC or NH 4 NO 3 –N was addedcompared with the control. The soil OM content in-creased each year during the application of SC; how-ever, little evidence for long-term accumulation of OMwas noted. Low NO 3 –N concentrations in the deepersoil layers posed no risk to water resources and no SC-relatedchangeswerenotedintheconcentrationsofP,K,Mg, or soil pH. ACKNOWLEDGMENTSThe authors would like to thank Brent Winters, GreenfieldEnvironmental Services, for his technical assistance. Partialfunding for this research was provided by Domtar Inc. and theOntario Ministry of Agriculture and Food. REFERENCES Bellaloui,A.,A.Chtaini,G.Ballivy,andS.Narasiah.1999.Laboratoryinvestigation of the control of acid mine drainage using alkalinepaper mill waste. 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The contribution of organic wastes to crop yields and soil fertility may be influenced by their composition and the soil type. This 6-yr study (2001―2006) evaluated the effects of repeated additions of mineral fertilizers (MF), mixed paper mill sludges (PMS) (18, 36, and 54 Mg ha ―1 ), dairy cattle manure (DCM) (36 Mg ha ―1 ) alone or with reduced mineral fertilizer (60% NPK) (RMF) and a control, on soil properties and corn (Zea mays L.), barley (Hordeum vulgaris L.), and soybean (Glycine max L. Merr.) yields in a clay loam and sandy loam. The applications of PMS and DCM increased mostly N mineralization and crop yields in the sandy loam than in the clay loam. However, increases of soil C contents, water-stable aggregates and MWD following their application were higher in the clay loam than in the sandy loam. The DCM effects on the soil property changes were of less magnitude than those of PMS. Except in the first year, the PMS applications at rates of 36 and 54 Mg ha ―1 without NPK, and PMS applied at a rate of 18 Mg ha ―1 with 60% NPK, produced highest crop yields in both soils and were comparable to those obtained with MF. The increase in yield following DCM additions (36 Mg ha ―1 ) was lower than that obtained with PMS. Annual MF applications increased crop yields in both soil without significant changes on soil properties. The benefits of PMS and DCM on soil properties and crop yields varied depending on organic wastes and soil type.

Large quantities of mixed paper mill sludges (PMS) are applied annually to agricultural soils in North America. However, little information exists in the literature delineating the impact of land application of PMS on crop N nutrition and soil properties. In a 3-yr field study, (1997-1999), we evaluated PMS effects on corn (Zea mays L.) yields and soil property changes. The study included annual and biennial PMS applications of 20, 40, and 60 Mg ha -1 on wet basis, applied alone or in combination with N fertilizer at reduced rates (90 and 135 kg N ha -1 for 40 and 20 Mg PMS ha -1 , respectively), complete N fertilizer for corn (180 kg N ha -1 ) and a control. Plots were split beginning with the second year for annual and biennial PMS and N fertilizer application. Annual or biennial applications of PMS alone resulted in grain yield increase of 1500 to 3000 kg ha -1 as compared to the unfertilized control. The applications of 20 to 40 Mg ha -1 PMS with N fertilizer at reduced rates (135 and 90 kg ha -1 respectively) achieved higher corn yields compared to PMS applied alone. The PMS applications combined with N fertilizer at reduced rates produced highest corn yields, similar to those obtained with complete N fertilization for corn (180 kg N ha -1 ). Corn apparent N recoveries (ANR) ranged from 17 to 21% in year of application and from 15 to 22% in residual year, depending of PMS rates. Three PMS applications at 40 to 60 Mg ha -1 yr -1 significantly increased the soil C content by 22 and 26%, and by 18 and 22%, compared to the control and N fertilizer, respectively. Those PMS applications also significantly increased the mean-weight diameter (MWD) of aggregates, and reduced soil bulk density as compared to the control and fertilizer alone treatment. The soil microbial biomass C and the alkaline phosphatase and urease activities were also increased in soils that received PMS. Our results suggest that the applications of PMS with low C/N (19-24) benefit corn growth possibly due to a combination of the higher nutrient availability and the improvement of the soil properties.

The current increase in oil and gas drilling activity has resulted in increased production of oil-base “mud” (OBM) in need of disposal. Land application of OBM to agricultural land is a common disposal technique that presents agronomic and environmental challenges since the material is rich in petroleum hydrocarbons. The objective of this study was to determine the effect of mixing OBM with bulking materials on hydrocarbon degradation and forage production after land application of the mixtures. An OBM was collected from Oklahoma and characterized for environmentally relevant properties such as total petroleum hydrocarbons (TPH) and trace metals. The OBM was bulked with either limestone, gypsum, or caliche, at a ratio of 3:1 or 1.5:1 bulking material/OBM. All mixtures were surface applied at equal TPH loading rates (8625 kg ha–¹) and soil samples taken at 7, 45, 60, and 170 d after application for evaluation of TPH, electrical conductivity (EC), pH, and sodium absorption ratio (SAR). After 7 d >50% of applied TPH degraded, which resulted in soil concentrations less than thresholds recommended for residential neighborhoods. By Day 170, 99% of applied TPH degraded. There was mostly no difference in TPH degradation as a function of type and amount of bulking agents used with OBM. Application of OBM did not significantly decrease forage yield compared to unamended control. Therefore, use of caliche, limestone, or gypsum bulked with OBM at a 1.5:1 ratio (bulking agent/OBM) would suffice for achieving acceptable TPH degradation when mixtures are surface applied and non-incorporated.

The evaluation of additives for the preservation of moist hay through fields experiments is made difficult by large and variable experimental units and environmental effects. A laboratory system was developed to rapidly screen hay preservative treatments. Ovendried hay was rehydrated with water and a preservative to the desired moisture concentration. Polyvinyl chloride (PVC) tubes provided the storage vessel. A constant initial density (200 kg m −3 ) was achieved using a mechanical press. Aeration was by diffusion through the open vessel top. Resistance to heat loss was provided by a fixed, polystyrene bed into which PVC tubes were inserted during a 21-d incubation at 25 o C (...)

The method of preservation of forage tissue may influence the quality and quantity of the product. Oven drying with hot air is widely used; however, enzyme activity and respiration are stimulated during the moisture reduction process. Criterion for selecting efficient drying conditions, such as sample density, kind of container (cloth or paper), and size of container were investigated using alfalfa (Medicago sativa L.) herbage. The dry matter, total nonstructural carbohydrate (TNC), starch, reducing sugar, and nonreducing sugar percentages were related to drying rate. Drying rate was linear until 80% dry weight was reached. Conditions requiring no more than 15 hours to reach 80% dry wt (density of 12 g dry wt per liter for paper sacks) were needed to hold loss within limits of experimental error for estimation of dry weight percentage. The TNC in all oven-dried samples was less than in freeze-dried tissue; however, data from cloth bags showed less loss and carbohydrate interconversion than paper sacks. Conditions requiring no more than 8 hours to reach 80% dry wt (density of 7 g per liter for paper sack) were required for sufficiently rapid drying to limit loss and interconversions of nonstructural carbohydrates within limits of experimental error. About twice this density was acceptable if cloth bags were used since the drying tune was reduced by about one-half with cloth as compared to paper containers that had equal densities. Acceptable bulk densities will differ with efficiency of the drying equipment, but time needed for drying to 80% dry wt should not exceed these limits.

Analyses of cotton burs produced in the snapping or sledding methods of harvesting cotton show that they do not possess a high feeding value for cattle without some form of hydrolytic treatment, such as has been proposed for increasing the digestibility of cottonseed hulls. They have no value as a source of furfural. The pentosan content is quite low, but they possess a content of cellulose which might possibly make them valuable as a source of pulp for paper, rayon, etc. That large quantities of inorganic fertilizer constituents are removed from the soil is evident from the ash analysis. This deficiency should be repaired either by application of artificial fertilizer or by returning the burs to the soil. The latter may be done either in the form of the ash, the whole burs, or preferably, by the artificially decomposed burs.

Kenaf (HibiscllS can.nabin~ L.), a potential pulp crop, ~as not show~ a consiStent ~Ield response to N, and the mfluence of N on pulp quality factors is unknown. The response of kenaf to lime and the amounts of various ~lements rem.oved with the harvested crop are also of mterest. A fIeld study was conducted to determine the effect of N on yield, mineral composition and quality of kenaf at two pH levels. Tests were conducted for 2 years! 1970 and 1971; in two .soil areas, Edisto (GlosslUJuic Fragmdalf) and Ona (TY,PlC Haplaguod); and in high a;nd 10';. pH areas esta~lished by prior applications of hme. NItrogen was applied at three levels and in single and three-way split applications. Nitrogen increased the yield, height and diameter of kenaf. Nitrogen had the favora;ble. effect of increasing woody fiber length, how­ ever ligrun content was also increased. Cellulose content w:'ls una~fected. Split applications of N usually produced hIgher yIelds than the same amount in a single application but were only significant for the first year on limed Edisto soil. Increasing rates of N decreased the P, K, Ca and B content of harvested kena£. Lime increased the Mg content anI reduced the Mn, AI, Sr, and Ba con­ tents. Neither N or lime had any significant effect on ZnZ Cu or Mo content.

Extensive analytical data on cottonseed hull bran are presented above. It is hoped that a better understanding of the constituents composing cottonseed hull bran thus obtained will lead to finding a more profitable outlet for this by-product of the cottonseed oil mills. The furfural yield is exceptionally high. Xylose, plus other pentoses, amounting to about 40%, and a crude cellulose content of 51% all indicate that cottonseed hull bran is a more valuable product than was heretofore thought to be the case.

Water-carriage methods of sewage disposal result in enormous losses of nitrogen, phosphoric acid, and potash. The new activated sludge process of sewage purification offers possibilities of fertilizer recovery from sewage. It produces a sludge of high nitrogen and phosphoric acid content, and the method deserves serious consideration as a conservation measure. Future improvements in the method may considerably increase the amounts of nitrogen and phosphoric acid recovered. Dried activated sludge produced with present day methods contains from 4.75 to 6.5% nitrogen and from 2.3 to 4.0% phosphoric acid. In pot tests in the greenhouse with oats activated sludge as a source of nitrogen proved about equal to cottonseed meal and fertilizer tankage and considerably better than digested leather. Field trials with cabbage, tomatoes, corn, and potatoes indicated that activated sludge is a satisfactory source of organic nitrogen for use in mixed fertilizers. Activated sludge exerts a favorable influence upon the mechanical condition of mixed fertilizers. It helps to prevent setting of the mixtures, makes uniform distribution easier, and reduces the danger of injury to the young sprout. In numerous trials on golf courses and lawns the use of activated sludge as the source of nitrogen in the fertilizer mixture has given excellent results.

A current estimate of global phosphorus use efficiency (PUE) for cereal production is not available. The objectives of this paper were to estimate PUE for cereal crops grown in the world and to review methods for improvement. Phosphorus use efficiency was determined using world cereal harvested area, total grain production, and P fertilizer consumption from 1961 to 2013, in addition to assumptions established from previous literature. World PUE of cereal crops was calculated using both balance and difference methods. Using the balance method, cereal grain P uptake is divided by the P fertilizer applied. Alternatively, the difference method accounts for P coming from the soil and that is subtracted from applied P. Utilized in this analysis is the estimate that cereal production accounts for 61% of the total harvested cropland. Cereal grain yields increased from 1.35 to 3.90 Mg h–¹ between 1961 and 2013. In 1961, the world’s fertilizer P consumption was 4,770,182 Mg and increased to 16,662,470 Mg of P fertilizer by 2013. This represents a 3.5× increase in P fertilizer consumption over 53 yr. Phosphorus use efficiency estimated using the balance method was 77%. Using the difference method, PUE for cereal production in the world was estimated to be 16%.

Impact of wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) straw removal from fields on soil organic C (SOC) is a concern. Increased animal populations and potential development of cellulosic ethanol production could increase the removal of straw from fields. This paper focuses on the effects of wheat and barley straw removal on SOC in irrigated production systems, and related the results to estimates of the minimum straw C inputs required to maintain SOC (MSC) from rain-fed systems. Six studies compared SOC changes with time in irrigated systems in which wheat straw was removed or retained. These studies indicated that SOC did not decline when residues were removed. Apparently belowground biomass is supplying C to irrigated soils at a rate sufficient to maintain SOC with time. However, under rain-fed systems, returning residue to the soil was required to maintain SOC. Estimates of MSC were obtained from nine rain-fed wheat system studies. Averaged across all rain-fed MSC values, 4.14 Mg more straw per ha was required to maintain SOC in rain-fed than in irrigated systems. Presently, the rain-fed based MSC values are the best information available to evaluating residue removal effects but caution should be used in applying these in irrigated systems. The results from this limited number of irrigated studies suggest that rain-fed estimates of MSC will overestimate the MSC in irrigated systems and underestimate the available irrigated straw resources. There is need to evaluate the effect of residue removal on SOC for diverse irrigated systems.

Traditional methods for chlorophyll (Chl) measurement include wet chemical extractions and handheld Chl meters. The recent availability of small and affordable radiometers has provided means to estimate Chl from reflectance measurements. This paper compares the performance of a handheld SPAD Chl meter and a recently developed Red Edge Chlorophyll Index (CI red edge ) for Chl estimation in grapevine (Vitis spp.) leaves. Leaves were sampled and Chl was quantified using these two methods. Both techniques were compared against grapevine-leaf Chl as analyzed using standard laboratory procedures. Both SPAD and CI red edge were equally accurate in measuring Chl < 300 mg/m2. However, at higher Chl, SPAD sensitivity declined and the CI red edge accuracy was much higher than that of SPAD. The Chl index was found to be capable of accurately estimating pigment contents across a greater range than the SPAD, thus it can be used for quantitative assessment of early stages of plant stress.

Chlorophyll meters have been widely used to diagnose N deficiencies in research trials and to help refine N fertilizer recommendations in production agriculture. The diagnoses are based on the assumption that chlorophyll meters can detect a wide range of N deficiencies under field conditions according to relationships between chlorophyll meter readings (CMRs) and yield responses to N fertilization that are established from small-plot trials. We conducted a field-scale study to evaluate the sensitivity of chlorophyll meters when they are used to detect N deficiencies in corn (Zea mays L.) production. The multiple year-location data were gathered in three cornfields where N fertilizer was applied at different rates in strips that crossed several soil map units. Grain yields were related to CMRs taken on corn leaves in June, July, and August of 1998-1999. Results showed that the chlorophyll meters could detect severe N deficiencies early in the season, but small and moderate deficiencies of N could not be diagnosed with reasonable certainty until it was too late to make in-season fertilization. Two types of discontinuity are discussed in this paper as likely causes for the limited sensitivity of the chlorophyll meters. Our study suggests that problems associated with the use of chlorophyll meters to diagnose deficiencies of N in production agriculture are much greater than their use to help interpret results of well-controlled research trials where yields are also measured.

Little information is available on the agronomic effectiveness of calcined nonapatite phosphate rock (PR) sources containing crandallite minerals in the form of Ca-Fe-Al-P for flooded and upland rice (Oryza saliva L.). We conducted laboratory and greenhouse studies to (i) characterize the mineralogical composition, (ii) investigate the solubility and dissolution behavior, and (iii) evaluate the agronomic effectiveness of two nonapatite PR sources (Juquia and Sapucaia) from Brazil and compared them with (i) a highly reactive Gafsa PR (Tunisia) containing apatite in the form of Ca-P and (ii) a reference water-soluble triple superphosphate (TSP) for flooded and upland rice. After calcination at 500°C for 4 h, the solubility of Juquia PR and Sapucaia PR in neutral ammonium citrate (NAC) significantly increased from almost nil to a maximum of 39.3 and 114 g P kg -1 , respectively. X-ray diffraction showed that crystalline crandallite mineral was transformed to an amophorus form after calcination. The solubility behavior of the two calcined PR sources followed the same trend as Gafsa PR, that is, P release decreased with increasing equilibrium pH in the 0.01 M KC1 solution (pH 3.0-8.0). At pH 3, the solubility followed: Gafsa PR > calcined Sapucaia PR > calcined Juquia PR. No P release was detected from any of the PR sources at pH ≥ 5.0 in the solution, indicating the Ca-P characteristic of the Ca-Fe-Al-P mineral controlled P dissolution of the calcined PR. Without calcination, both Juquia PR and Sapucaia PR were totally ineffective for upland rice grown on a Hiwassee clay loam (fine, kaolinitic, thermic Rhodic Kanhapludult) with pH 5.4 whereas a significant P response was observed with the calcined PR samples. For flooded rice grown on Hiwassee soil, the calcined Juquia PR and Sapucaia PR were 66 and 72%, respectively, as effective as TSP in increasing rice grain yield whereas Gafsa PR was ineffective. For upland rice grown on the unlimed soil, Gafsa PR was as effective as TSP in increasing rice grain yield whereas calcined Juquia PR and Sapucaia PR were 89 and 83% of TSP. The effectiveness of Gafsa PR was reduced to 0% after the soil was limed to pH 7.0 whereas the two calcined PR sources were reduced to 49% of TSP. Soil available P extracted by iron oxide impregnated filter paper (Pi test) or anion-exchange resin after rice harvest correlated well with P uptake by rice grain for flooded and upland rice.

Simulating grain (N g ) and straw (N s ) nitrogen (N) concentration is of paramount importance in cropping systems simulation models. In this paper we present a simple model to partition N between grain and straw at harvest for barley (Hordeum vulgare L.), wheat (Triticum aestivum L.), maize (Zea mays L.), and sorghum (Sorghum bicolor Moench). The principle of the model is to partition the aboveground N at physiologic maturity based on the relative availability of biomass and N to the grain. The inputs for the model are the harvest index (HI), representing the relative availability of biomass to the grain, and the aboveground N concentration (N t ) at harvest, representing the availability of N. The model has five parameters, of which four (the maximum and minimum achievable grain and straw N concentrations) are readily available; the parameter C requires calibration. The model was calibrated and tested for these four species without differentiating genotypes within species. The testing included diverse experiments in wheat; comparing observed and estimated N g the relative RMSE ranged from 3 to 10% (five experiments) and was 31% in one experiment in which the estimated N g exceeded consistently the observed values. For barley, maize, and sorghum, the data availability for testing was limited, but the model performed well (relative RMSE values of 7, 7, and 18%, respectively). Therefore, the model proposed seems to be robust. It remains to be determined if the parameters and the method are useful to discriminate genotypic differences in N g within a species and if the method can be applied to legume crops.

Although some mathematical models exist to assist in deciding whether or not to apply phosphate rock (PR) to soils as a source of P, these models focused either on the use of highly soluble PR sources, mainly for pastures, or were too impractical for field use. There was, therefore, a need to develop a Phosphate Rock Decision Support System (PRDSS) with more comprehensive capabilities to predict the relative agronomic effectiveness (RAE) of PR with respect to water-soluble phosphorus (WSP) fertilizers at field and farm level. The PRDSS includes PR sources varying widely in solubility and different crop species grown on variable soil properties and rainfall conditions. In this paper, we describe the development and use of the mathematical model, PRDSS, to estimate RAE of PR sources with respect to WSP fertilizers and to calculate a simple index to be used for preliminary economic comparison of these two types ofP sources. The PRDSS is able to function with a minimum input of only soil pH, the name of the mine that is the source of the phosphate rock, and the species of crop to be grown. A more accurate prediction of RAE is obtained from the PRDSS when more detailed data describing the soil, crop, and weather are included as inputs.

Interactions among environmental factors, management decisions, and field characteristics cause temporal and spatial variability in corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] yields. The objectives of this paper are (i) to test whether yield response of corn to N and P and of soybean to P are spatially and temporally stable, and (ii) to evaluate the profitability of a variable rate (VR) N and P fertility management strategy over a 5-yr, corn–soybean rotation using this response information. A field near Windom, MN, USA, was cropped with corn (1997, 1999, and 2001) and soybean (1998, 2000). Three replications of 13 N and P treatments were established in a split-plot arrangement of a randomized complete block design. Treatments were applied at constant rates in strips across the entire field. Fertilizer N treatments were 0, 67, 112, 157, and 202 kg ha 21 and P treatments were 0, 56, and 112 kg P2O5 ha 21 . The field was partitioned into sub-blocks for spatial analysis of yield response. Corn and soybean response to these inputs was estimated for each block, each year. Results indicate that spatial variation of crop response to these inputs is significant, and that response of corn and soybean to P is temporally stable in some parts of the field, but not others. Response to N was not temporally stable. Results of an ex post profitability analysis found that average returnsoverthe5-yrperiodfromtheVRNandPmanagementstrategy were $28 ha 21 higher than returns from a uniform application strategy.

knowledge of crop N need may be used by producers to guide future fertilizer-N management thereby improving The end-of-season stalk nitrate test provides a method of assessing profitability and reducing environmental degradation. the N available to the corn (Zea mays L.) crop during the latter part ofthe season.This studywas conductedto determinehow stalknitrate To be a useful crop management tool, methods for test results and interpretations are affected by sample composition. collecting and analyzing samples must be straightforStalkswere collectedfrom threefieldsites andseparated intophytom- ward and reasonably flexible so producers and consulers (node plus internode above), which were subdivided into three tants can adapt to field conditions as they gather samor five segments after length was measured. Nitrate-N concentration ples. It is unrealistic to assume that samples will always of phytomers decreased linearly from the soil to the ear. Within a be exactly 20-cm long and can always be collected bephytomer, segments also decreased acropetally (from base to apex). tween 15 and 35 cm above the ground under field situaNode tissue NO3–N concentration did not differ from that of the tions. For example, if samples are collected after cominternode segment immediately above the node. Weighted means bine harvest, the specified stalk segment (Binford et al., were used tocompute NO3–N concentration ofstalk samples collected 1990) may be destroyed or severely damaged and there5 cm higher (from 20 to 40 cm above the soil) or lower (from 10 to 30 cm above the soil) on the stalk than in the original method (from fore inappropriate for use in assessing late-season N 15 to 35 cm above the soil). Although the three samples (10–30, 15–35, nutrition of the crop. The objective of this study was to and 20–40 cm) differed in NO3–N concentration, the difference was determine the distribution of nitrate by phytomer (node only about 15% compared with the 25% difference in sampling posi- and the internode above) within stalks of corn and how tion (5 cm of 20-cm sample length). The phytomer nearest the soil stalk nitrate test results and interpretations would be had 35 to 40% greater NO3–N concentrations than the section of stalk affected if samples were collected from a portion of the 15 to 35 cm above the soil. Critical values delineating yield-limiting, stalk different from that specified in the original method adequate, and excessive N availability should be modified if stalk (Binford et al., 1990). sectionsotherthanthestandard15to35cmsectionareused.However, the qualitative nature of the stalk nitrate test and the range of NO3–N MATERIALS AND METHODS concentrations observed with reasonable corn cultural practices (1000) make this test quite robust and precise definition of sample At physiological maturity, stalks were collected from 20 composition and critical values less necessary. corn plants grown in a rainfed, general production field at the Agronomy Havelock Farm, Lincoln, NE, to conduct initial analyses (designated the 20-stalk experiment in the remainder of the paper). NC hybrid 4880 was planted in late April at T he end-of-seasoncorn stalk nitrate test (hereafter about 49 000 plants ha 1 . Nitrogen was applied pre-plant at referredtoasthestalknitratetest)wasproposedand 140 kg ha 1 as anhydrous ammonia. Weeds were controlled advocated by Binford et al. (1990) as a method of deter- bya combinationof pre-emergenceherbicides andcultivation. mining if excessive or insufficient N was available to the Crop yield was 6.35 Mg ha 1 . Stalks were randomly assigned corn crop during the latter part of the season. In the test, to 1 of 10 replications. Leaves were removed and stalks air20-cm segments of corn stalks (between 15 and 35 cm dried before processing. During processing, stalks were cut above the soil) are collected from several plants (10), immediately below each node. Each phytomer was further dried, ground, and analyzed for nitrate-N. Nitrate-N con- divided into six pieces: the node and five equal-length pieces centrations 700 mg kg 1

Midseason fertilizer N is currently recommended using a wide range of differing soil-test, plant-test, and soil-N mineralization procedures. The objective of this paper is to present an applied approach for determining midseason fertilizer N rates. A conventional 2003 Honda FourTrax Foreman ES four-wheeler (433 cc, 127 cm wheel base, 116 cm wide) with a 3 m wide spray boom and a 1-m spacing between nozzles was modified to deliver a range of fixed N rates as urea ammonium nitrate (28%N) within a 9 m 2 grid. Within each grid, nine separate 1 m 2 areas exist, whereby each of the four corners receive no fertilizer N. Rates of 22, 45, 67, 90, and 112 kg N ha -1 occupy the other five, 1 m 2 areas within the 9 m 2 grid (termed as an N rate calibration stamp). Traveling at 8 km h -1 (5 mph), consecutive 9 m 2 grids can be applied continuously. Calibration stamps should be applied preplant or soon thereafter and superimposed on top of the farmer practice. By midseason, differences between the 1 m 2 N rate areas can be visualized and a field-specific topdress N rate prescribed by choosing the lowest N rate where no visual differences were observed between it and the highest rate. Calibration stamps applied preplant or soon after planting can assist in providing visual interpretation of N mineralization + atmospheric N deposition from planting to the time midseason N is applied, and improved determination of topdress N rates.

Although use of no-tillage in cotton (Gossypium hirsutum L.) pro duction in the southeast USA has dramatically increased recently, reports of reduced seedling emergence, poor plant establishment, reduced growth, delayed maturity, and low yields still constrain adoption. The objective of this study was to evaluate the effect of tillage systems on growth and yield of cotton grown in rotation with a winter rye (Secale cereale L.) cover crop with poultry litter and ammonium nitrate fertilizer application in north Alabama. Results from 1996 to 2001 are reported in this paper. Treatment factors were three tillage systems, two cropping systems, two N sources, and four N levels. Winter rye cover cropping increased surface residue cover by up to 35, 70, and 100% in conventional tillage, mulch tillage, and no-tillage systems, respectively. Despite initial differences in rate of seedling emergence, final seedling establishment averaged 10 seedlings m -1 in all treatments. At the rate of 100 kg N ha -1 , the effect of poultry litter on cotton growth and yield parameters was generally lower or similar to that of ammonium nitrate at the rate of 100 kg N ha -1 . However, at 200 kg N ha -1 , poultry litter improved cotton growth and lint yield compared with ammonium nitrate at 100 kg N ha -1 or poultry litter at 100 kg N ha -1 . Cotton lint yields averaged over all treatments ranged from 1128 to 1405 kg ha -1 over the study period. With adequate N fertility from poultry litter, no-tillage and mulchtillage systems with winter rye cover cropping are ideal for cotton production in the southeast USA.

Acidic Typic Cryoboralf soils amended with wood ash can raise soil pH and can supplement plant growth by adding minerals and micronutrients. However, presence of other elements in soils such as Cd, S, and Zn can affect plant growth and seed quality. In an earlier paper, we have shown that wood ash applications on Typic Cryoboralf and Typic Cryocrept soils in Alberta, Canada, increased canola (Brassica rapa L.) yield by 72%. In this study, the effect of a single application of 0, 6, 12.5, and 25 t ha -1 (dry weight) wood ash on oilseed quality, based on oil, protein, chlorophyll, and glucosinolate content, was examined over three growing seasons from 1998 to 2000. Seed oil and protein content of ash-treated plots either increased or remained the same as controls. In contrast, significant increases (p 0.05). Levels of B in ash-treated soils were different from each other but not from the controls (P < 0.05). Cadmium levels were below detection limits for the instrumentation used (0.08 mg kg -1 ). These results indicate that use of wood ash on acidic soils has the potential to increase seed oil content but may adversely affect quality of the oilseed produced.

rThe Ohio Management Systems Evaluation Areas (MSEA) project focused on developing and evaluating improved agricultural management systems and predictive models. The Root Zone Water Quality Model (RZWQM) is an environmental model for simulating water, chemical, and biological response of agricultural management systems. This paper presents calibration and evaluation of the generic plant production model of RZWQM, as well as some evaluation results for the nitrate and soil water content predictions. Corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] biomass data collected at the Ohio MSEA from 1991 to 1993 were used for evaluation. Data from 1992 were used in calibrating RZWQM, and data from two other years (1991 and 1993) at the same site were used for validation. Crop growth predictions were compared with observed values of leaf, stem, and seed biomass collected throughout the growing season. Leaf and stem biomass predictions generally fell within 1 SD of the observed values, but for all years there were dates when predictions were outside of the observed range. RZWQM predicted seed biomass or yield adequately for all 3 years, with predictions falling within 1 SD of the observed values. Soil water content estimates for corn were higher than observed values late in the season, perhaps because of underestimates of evapotranspiration due to errors in leaf area predictions. The model overpredicted nitrate concentrations for the corn plot late in the season. Nitrate concentrations for the soybean plot were generally underpredicted. These differences may be due to underestimates of the fast humus pool of the nutrient model and of the N 2 fixation rate for soybean. More evaluation is needed to refine the nitrate and soil water content predictions.

Methods of drying forage samples were examined for their influence on the total C, N, and dry matter (DM) content of 'Range? alfalfa (Medicago sative L.). Forage samples were freeze-dried; air-dried in perforated paper bags and on trays; dried in perforated paper bags in mechanical convection ovens at 60, 80, and 100 C; and oven-dried at 100 C for 90 minutes followed by drying at 60 C, or by air-drying. All treatments were terminated after 48 hours. Losses in C and N were measured by changes in C:K and N:K ratios. The DM losses were measured by changes in R. concentration. Carbon and DM were lost more readily than N by either respiratory or thermochemical processes. These losses resulted in an apparent concentration of N in all forage dried between ambient and 100 C. All treatments, when compared to freezedrying, resulted in losses of C and DM. The greatest loss of DM, 5.4% occurred in samples dried at 100 C. Oven-drying at 100 C for 90 minutes followed by airdrying caused DM losses of only 0.2%. Significant differences in actual N content between the various drying methods were not generally observed.

Allelopathic inhibition typically results from the combined action of a group of allelochemicals which, collectively, interfere with several physiological processes. The objectives of this paper are to summarize research that illustrates the joint action of allelochemicals, and to provide evidence that both the amount and detrimental action of these compounds depends on the extent of associated abiotic and biotic stresses. Allelopathy is strongly coupled with other stresses of the crop environment, including insects and disease, temperature extremes, nutrient and moisture variables, radiation, and herbicides. These stress conditions often enhance allelochemical production, thus increasing the potential for allelopathic interference. In the paradigm of interactions, the data indicate that crops are more sensitive to allelopathy when moisture, temperature, or nutrient conditions are less than optimal. For example, the inhibition threshold concentration for ferulic acid to affect seedling growth was reduced with even minor moisture stress (ψ = - 0.15 MPa) or a growth temperature at the higher end of the normal range for a species. Under greenhouse conditions, additive inhibition resulted from the joint action of ferulic acid with low levels of alachlor [2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)acetamide], atrazine [6-chloro-N-ethyl-N'(1-methylethyl)-1,3,5-triazine-2,4-diamine], or trifluralin [2,6-dinitro-N,N-dipropyl-4-(trifluoro-methyl)benzenamine]. Interactions of multiple stresses in crop environments will determine the relative impact of allelopathy. Allelopathystress interactions also have implications for herbicide and residue management strategies, crop rotations, biological control measures, and tillage practices that can contribute to a more sustainable agriculture.

Lodging of perennial ryegrass (Lolium perenne L.) seed crop is a widespread problem. Crop lodging reduces seed yield and interferes with seed harvest. This study was conducted to determine if low rates of paclobutrazol [(2RS,3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1H-1,2,4-triazol-1-yl)-pentan-3-ol] influences seed yield and yield components of perennial ryegrass cv. Pennfine. Paclobutrazol was applied at either spikelet initiation or floret initiation at 0, 0.50, or 0.75 kg a.i. ha⁻¹. Paclobutrazol delayed the onset and reduced the severity of lodging. Averaged over the application timings, the 0.5 and 0.75 kg ha⁻¹ rates increased seed yield by 87 and 114% in 1983, respectively, and by 56 and 75% in 1984. No difference was observed between application timings in 1983, but in 1984 paclobutrazol had a greater effect in reducing lodging and increasing seed yield when applied at spikelet initiation rather than at floret initiation. Increases in seed yield were associated primarily with improvements in the number of seed set per spike, although paclobutrazol applied at spikelet initiation in 1983 also increased the number of spikes at maturity. Paclobutrazol did not affect straw weight, but increased harvest index in both years. Paclobutrazol, however, slightly reduced seed weight. We concluded that under western Oregon conditions, paclobutrazol rate as low as 0.5 kg a.i ha⁻¹ applied at spikelet initiation can significantly reduce lodging and increase perennial ryegrass seed yield, although rates greater than 0.75 kg a.i. ha⁻¹ may be required to achieve maximum yield. Contribution from the Oregon Agric. Exp. Stn., Tech. Paper no. 10811.

High soil temperatures are a significant constraint to crop establishment. Exposure of preemergent maize (Zea mays L.) to temperatures in excess of 40°C stops shoot elongation and may also damage the seedling, reducing subsequent shoot growth in the physiological temperature range (9 to 40°C). At present, there is little quantitative understanding of the effects of high temperature stress on preemergent maize shoot growth. Consequently, existing maize emergence or preemergent maize shoot growth models are restricted to the physiological temperature range. The work described in this paper quantified the effect of supramaximum temperatures (temperatures greater than 40°C) on maize shoot growth, and in particular on its component parts, the coleoptile and first internode. The major impact of supramaximum temperatures on shoot growth was due to a severe reduction in the first internode growth rate, which was correlated with the maximum temperature reached during the day. We also found that, under diurnally varying temperature conditions, coleoptile growth ceased only at 45°C, rather than at 40°C as found previously in constant temperature experiments. Inhibition of shoot growth due to high temperature damage was alleviated when seedlings were grown in the physiological temperature range for 33 h. Based on these findings, a model was developed that can predict shoot growth of seedlings exposed to supramaximum temperatures. The model successfully predicted shoot growth of seedlings exposed to supramaximum temperatures as a part of the diurnal cycle. The model was unable, however, to predict seedling recovery from high temperature damage.

Weeds interfere with big bluestem (Andropogon gerardii Vitman var. gerardii Vitman) and sand bluestem [Andropogon gerardii vat. paucipilus (Nash) Fern.] establishment on rangeland and cropland in the central, Great Plains of North America. A study was conducted to determine if metolachlor [2-chloro-N-(2-ethyl-6-methylpbenyl)-N-(2-methoxy-1-methylethyl)acetamide] and atrazine [6-chloro-N-ethyI-N′-(1-methylethyl)-1,3,5-triazine-2,4-diamine] applied preemergence could improve stablishment of big bluestem and sand bluestem cultivars. ‘Bonilla’, ‘Pawnee’, ‘Kaw’, and ‘Rountree’ big bluestem and ‘Goldstrike’ sand bluestem were planted in late May to early June 1989 and 1990 near Clay Center [Sharpsburg silty clay loam (fine, montmorillonitic, mesic Typic Argiudoll)] and Mead [Hastings silt loam (fine, montmorillonitic, mesic Udic Argiustoll)] in Nebraska. Metolachlor at 2.2 or 3.3 kg a.i. ha⁻¹ and atrazine at 2 kg a.i. ha⁻¹ were applied alone or in combination before weeds or seeded grass cultivars emerged. Stand frequency (the number of times the planted grasses occurred within sampling grids and expressed as a percentage of the total number of grids evaluated) and yield of the grass cuitivars were measured the year after planting to determine establishment success. Grass stand frequencies were usually >50%, with or without herbicide treatment. Yield of big bluestem and sand bluestem cultivars was increased by at least 30% when herbicides were applied preemergence the year of planting compared with yield without herbicide. For each cultivar, yield and stand frequency were similar when metolachlor or atrazine at 2.2 kg a.i. ha⁻¹ were applied. Therefore, metolachlor is a suitable replacement for atrazine to improve establishment of big bluestem and sand bluestem cultivars. However, yield and stand frequency of most grass cultivars were maximized when metolachlor and atrazine were applied in combination. Joint contribution of the USDA-ARS and the Nebraska Agric. Res. Div., Journal Series no. 10654. Mention of pesticides in this paper does not imply registration under FIFRA nor does it constitute a recommendation by the USDA-ARS or the Univ. of Nebraska-Lincoln.

Inherent in the ongoing transition from open-field burning to nonburn systems for grass seed production in the Pacific Northwest is an increased reliance on herbicides for weed control. However, herbicide treatments able to control volunteer crop seedlings, the most abundant weed in certified grass seed fields, may pose severe hazards to the established crop itself. Fourteen herbicide treatment sequences plus an untreated check were examined in five residue removal systems at two sites during two consecutive growing seasons to determine their impact on perennial ryegrass (Lolium perenne L.) seed yield. Seed yield was reduced by weed competition in nonburned, untreated checks, and by herbicide injury in some of the 14 herbicide treatment sequences. When compared across 13 promising herbicide treatments, seed yield did not differ between burned and nonburned plots in the first year, although burning was slightly superior in the second. However, the cumulative yield advantage to burning was only 84 kg ha−1 , or 2.6%, over the 2-yr period. Although differences in yield among four herbicides applied preemergence (PRE) to seedling grasses in mid-October were relatively small, pendimethalin [N-(l-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine] and oxyfluorfen [2-chloro-l-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl) benzene] were superior to either metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-l-methylethyl)acetamide] or trifluralin [2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenamine] in specific instances. When applied following PRE herbicides, early December postemergence (POST) applications of 1.8 kg ha −1 diuron [N'-(3,4-dichlorophenyl)-N,N-dimethylurea] or 0.14 kg ha−1 oxyfluorfen plus 1.3 kg ha −1 diuron generally did not differ in yield. While there was usually little net effect on seed yield of applying POST herbicides following pendimethalin, they did depress yield 129 kg ha−1 the first year in burned plots, while increasing it an average of 79 kg ha~* the second year in all plots. With properly chosen herbicide treatments, the impact on perennial ryegrass seed yield of changing to nonburned methods of residue removal should be minimal. If such herbicide treatments are not available, however, the elimination of field burning may seriously disrupt perennial ryegrass seed production. Contribution of the USDA-ARS in cooperation with the Oregon State Univ. Agric. Exp. Stn. Oregon State Univ. Tech. paper no. 10,214.

Temperature is a primary environmental factor affecting cotton growth. Information on temperature effects on Pima cotton (Gossypium barbadense L.) growth is limited. The objective of this paper is to provide quantitative estimates of temperature effects on leaf emergence rates, the duration of leaf expansion, and rate of expansion. Pima cotton plants were grown from seed in naturally lit controlled environments with unlimited water and nutrients under five day/night temperature regimes ranging from 20/12 to 40/32°C. Weighted average daily temperature was calculated from 900-s average temperatures. Carbon dioxide was maintained at 350 μL L −1 during the daylight hours. Leaf area expansion and biomass accumulation were monitored from emergence to 64 d after emergence [...]

Kenaf (Hibiscus cannabinus L.) is an excellent supplement to wood as a source of fiber for paper pulp. With the introduction of kenaf into the western USA, plantings may be on soils where salinity problems already exist or may develop from the use of saline irrigation water. Because of the lack of salt-tolerance information on mature vegetative growth and yield, a 2-yr field-plot study was conducted at Brawley, CA. Two cultivars (Everglades-41 and 7818-RS-10) were grown with six salinity treatments imposed on a Holtville silty clay [clayey over loamy, montmorillonitic (calcareous), hyperthermic Typic Torrifluvent]. Electrical conductivities of the irrigation waters, containing NaCl and CaCl 2 (1:1 by weight), were 1.1, 2.0, 3.0, 4.0, 5.0, and 6.0 dS m −1 (...)

Ethephon ([2-chloroethyl] phosphonic acid), typically increases barley (Hordeum vulgare L.) spikes per square meter by increasing the frequency of late emerging green tillers, resulting in uneven crop maturity. This study was conducted to evaluate barley tiller grain yield and malting quality response to plant density and ethephon, with special reference to late-emerging green tillers. Field studies were conducted at Povvell. WY between 1987 and 1989 on a Garland clay loam (fine, mixed, mesic Typic Haplargid). Target plant densities of 150 and 300 plants nr2 were established. Ethephon was applied at the Zadoks growth stages (ZGS) of 13, 32, or 39, and one treatment was split-applied at ZGS 32 and 39. Early emerging primary tillers (Tl, T2, and T3) and the main shoot contributed 86% of the total grain yield at high plant density vs. 73% at lo * plant density. In general., increasing plant density resulted in progressively greater differences for kernel plumpness and kernels per spike on the MS, Tl, T2, and T3. Ethephon applied at ZGS 39 reduced plant height 6 to 15 cm depending on year. Lodging was reduced by ethephon application, although the lodging level was low in every year of the study. Ethephon did not affect grain yield or protein content, but it often reduced volume mass and kernel plumpness compared to the untreated control. Regardless of ethephon treatment, kernels on late emerging tillers were of lower mass, volume mass, and plumpness than kernels on early emerging tillers;. Ethephon applied at ZGS 39 increased the number of late emerging green tillers by 225 spikes nr2 compared with the control. These late emerging green tillers contributed 8% to the total grain yielc, but produced grain of substandard malting quality. Dep. of Plant, Soil and Insect Sciences, Univ. of Wyoming, UWREC, 747 Road 9, Powell, WY 82435. Contribution of the Wyoming Agric. Exp. Stn. Journal paper no. 1616. Received 9 July 1990.

(...) Since ion-chromatography has demonstrated versatility in inorganic ion analysis, it was adopted in this paper to measure SO 4 in wet acid digests of plant materials. Plant tissues (200 mg) were digested with 2 mL HNO 3 + 1 mL 70% HClO 4 and subsequently evaporated to dryness in order to minimize the HClO 4 concentration for efficient ion-chromatography. Magnesium oxide was dissolved in HNO 3 at a rate of 1.25 gL −1 to provide cations to prevent the losses of S gases. Dionex OmniPac PAX-500 analytical column was used to provide simultaneous anion exchange and reverse-phase ion-chromatography (...)

A method to isolate large quantities of non-mesophyll cell wall material for studying factors that limit the susceptibility of these cell wall polysaccharides to microbial degradation was evaluated. Mesophyll cells were separated from non-mesophyll cells in indiangrass (Sorghastrum nutans [L.] Nash) leaf blades by ball milling to separate cells and then sieving to isolate non-mesophyll cells. The mesophyll fraction was comprised of non-lignified mesophyll cells contaminated with some fiber (sclerenchyma, xylem, and bundle sheath) particles. The non-mesophyll fraction was virtually free of mesophyll cells and consisted primarily of lignified cell wall material. The weight ratio of mesophyll to non-mesophyll cell wall material was 1.21. Non-mesophyll cell walls were similar to mesophyll cell walls in their concentrations of arabinose, mannose, and galactose, and higher in their concentrations of xylose, glucose, p-coumark acid, and ferulic acid. The ratio of xylose to arabinose was significantly greater for the non-mesophyll fraction. Compositional differences between non-mesophyll and mesophyll cell walls may in part explain the lower susceptibility of non-mesophyll cell wall material to microbial degradation compared to mesophyll cell wall material. Contribution from the Missouri Agnc. Exp. Stn. journal paper no. 10,960

Long-term experiments play a vital role in revealing dynamic soil and weather processes that directly influence sustainable crop production and ecosystem health. The objective of this review paper is to present one of the oldest long-term continuous winter wheat (Triticum aestivum L.) experiments, the Magruder Plots, and their contribution to the scientific community regarding questions of yield response to amendments, yield stability, percentage organic matter (OM) lost over time, soil nutrient status, microbial activity, weed population, and information on the economic return from winter wheat production. Alexander C. Magruder initiated the experiment in 1892 and is in progress to date. The original plot was started to evaluate wheat production on native prairie soils without fertilization. After 6 yr the principal investigator split the initial plot into two and fertilized one half with cattle manure. The experiment was then modified to include 10 treatments in 1930 by Dr. Horace J. Harper to answer several soil fertility related questions. Since 1947, six treatments have remained intact that evaluate simple combinations of manure, and inorganic N, P, K, and lime. Following 114 yr of continuous winter wheat production under conventional tillage, the check plot that has never received any fertilizer addition continues to produce wheat grain yields of >1 Mg ha -1 . Despite the decline in soil organic matter from 4 to 1% during this time period, wheat grain yields continue to show slight increases with time, likely due to improved genetics. While continuous wheat without rotation is not recommended, this 114-yr study documents the feasibility.