bluuebunny/crossref_metadata_2025 huggingface dataset:
Impact of Tillage on Root Systems of Winter Wheat
Authors: Qin Ruijun , Stamp Peter , Richner Walter
Published: July 2010

There is relatively little information about root growth response under different tillage systems in cool temperate regions. In a 5‐yr field trial at two sites [loamy silt (1995–1999) and sandy loam soils (1996–2000)] in the Swiss midlands, the effect of tillage intensity [no‐tillage (NT) and conventional tillage (CT)] on the morphology and distribution of winter wheat (Triticum aestivum L.) roots at harvest was studied for 3 yr (1997–1999). The root length density (RLD), mean root diameter (MD), and relative length per diameter‐class distribution of the roots were determined using washed roots from soil cores taken from the row and the midrow. Averaged across all the other factors, NT resulted in a slightly lower RLD and a slightly larger MD compared with CT. However, compared with CT, the RLD was higher in the upper soil layer (0 to 5 cm), similar from 5 to 10 cm, and lower from 10 to 30 cm in NT. The tillage effect disappeared below 30 cm. This tillage‐induced difference in root distribution was more and more marked from 1997 to 1999. In the row, the MD was greater from 0 to 15 cm, was similar down to 25 cm, and was smaller from 25 to 50 cm in NT compared with CT while below 50 cm, the MD was hardly affected by tillage intensity. However, MD in the midrow was usually significantly higher from 0 to 10 cm under NT than under CT.
Comparative Morphology of Caucasian Old World Bluestem and Native Grasses
Authors: Harmoney Keith R. , Hickman Karen R.
Published: July 2010

Caucasian old world bluestem (OWB) [Bothrichloa bladhii (Retz) S.T. Blake] has been widely introduced in the southern and central Great Plains as a perennial warm‐season grass for forage and soil conservation. As a result of its widespread introduction, it has escaped into some native rangelands. Once established in native pastures, observations suggest that Caucasian OWB may mature earlier than native vegetation and may be avoided by grazing animals in mixed rangelands, thus altering grazing distribution and over utilizing native species. More advanced morphological development in grasses is also associated with lower forage quality and lower palatability. This study was conducted to examine if morphological development of Caucasian OWB and native perennial warm‐season grass species differs. Monoculture stands of Caucasian OWB, big bluestem (Angropogon gerardii Vitman), little bluestem [Schizachyrium scoparium (Michx.) Nash], and side‐oats grama [Bouteloua curtipendula (Michx.) Torr.] were established in the spring of 2000. After the initiation of first growth in 2002 and 2003, vegetation was hand clipped each week for 8 wk and quantified for morphological stage of development according to the Nebraska staging method. In 2002, a drought season, Caucasian OWB had a greater mean stage weight (MSW) than the native species during Weeks 3 through 7 (P < 0.001). In 2003, Caucasian OWB began the season at a similar morphological stage as the native species, but had a rate of development that was 5 to 11 times greater than the native species. The last 3 wk of the sampling period, MSW of Caucasian OWB was greater than all three native species (P < 0.001). With more advanced morphological development in Caucasian OWB than the native grasses, declining forage quality could affect grazing preference and distribution patterns in mixed swards of Caucasian OWB and native species. The introduction of Caucasian OWB into native rangelands may have impacts that have yet to be understood.
Evaluating Soil Color with Farmer Input and Apparent Soil Electrical Conductivity for Management Zone Delineation
Authors: Fleming K. L. , Heermann D. F. , Westfall D. G.
Published: July 2010

Variable rate fertilizer application technology (VRT) can provide an opportunity to more efficiently utilize fertilizer inputs; however, accurate prescription maps are essential. Researchers and farmers have understood the value of dividing whole fields into smaller, homogeneous regions or management zones for fertility management. Management zones can be defined as spatially homogeneous subregions within a field that have similar crop input needs. Delineating management zones that characterize the spatial variability within a field may provide effective prescription maps for VRT. The objective of this research was to compare and evaluate management zones developed from soil color (SC) and farmer experience with management zones developed from apparent electrical conductivity (ECa). These two methods of developing management zones were compared with soil nutrient levels, texture, and crop yields collected on two fields in 1997. The soil and yield parameters followed the trends indicated by both management zone methods at Field 1 with the highest values found in the high productivity zones and the lowest the low productivity zones. Significant differences were found among the management zones. However, at Field 2 the high and medium productivity zones were generally not significantly different using the SC approach, whereas the ECa approach was effective in identifying three distinct management zones. Both methods of developing management zones seem to be identifying homogeneous subregions within fields.
Forage Production and Phosphorus Phytoremediation in Manure‐Impacted Soils
Authors: Pant H. K. , Adjei M. B. , Scholberg J. M. S. , Chambliss C. G. , Rechcigl J. E.
Published: July 2010

Amounts of manure generated by concentrated animal operations often exceed the capacity of nearby land, and stricter environmental regulations lead to creation of pockets of highly impacted sites within a watershed basin. Linking forage production with manure utilization can be an effective approach for addressing both the problems of manure disposal and impact reductions on water quality. In general, cropping patterns, climate, topography, and fertilization practices affect concentrations of nutrients, including N and P in runoff waters. Forage plants include diverse groups of grasses and legumes adapted to different climatic zones and varying soil fertility. To optimize the P remediation in affected sites, knowledge of P forms and soil properties is crucial. Given the possibility of producing high quality and quantity of herbage from such impacted agricultural areas, it would be worthwhile to utilize existing knowledge of herbage production from differentially manured soils and optimize nutrient uptakes. This review attempts to consolidate the available information on the potentials and limitations of pasture usage for phytoremediation of P in affected soils. Such herbage production systems may not only be environmentally sound for recycling of nutrients and minimizing nutrient loss to water bodies, but they may also help farmers/producers to maintain a profitable business enterprise.
The Contribution of Commercial Fertilizer Nutrients to Food Production
Authors: Stewart W. M. , Dibb D. W. , Johnston A. E. , Smyth T. J.
Published: July 2010

Nutrient inputs in crop production systems have come under increased scrutiny in recent years because of the potential for environmental impact from inputs such as N and P. The benefits of nutrient inputs are often minimized in discussions of potential risk. The purpose of this article is to examine existing data and approximate the effects of nutrient inputs, specifically from commercial fertilizers, on crop yield. Several long‐term studies in the USA, England, and the tropics, along with the results from an agricultural chemical use study and nutrient budget information, were evaluated. A total of 362 seasons of crop production were included in the long‐term study evaluations. Crops utilized in these studies included corn (Zea mays L.), wheat (Triticum aestivum L.), soybean [Glycine max (L.) Merr.], rice (Oryza sativa L.), and cowpea [Vigna unguiculata (L.) Walp.]. The average percentage of yield attributable to fertilizer generally ranged from about 40 to 60% in the USA and England and tended to be much higher in the tropics. Recently calculated budgets for N, P, and K indicate that commercial fertilizer makes up the majority of nutrient inputs necessary to sustain current crop yields in the USA. The results of this investigation indicate that the commonly cited generalization that at least 30 to 50% of crop yield is attributable to commercial fertilizer nutrient inputs is a reasonable, if not conservative estimate.
Development of Near Infrared Reflectance Spectroscopy Calibrations to Estimate Legume Content of Multispecies Legume–Grass Mixtures
Authors: Locher F. , Heuwinkel H. , Gutser R. , Schmidhalter U.
Published: July 2010

Legume content in legume–grass mixtures is a key parameter for the quantification of N2 fixation, forage, and diet quality. This study was conducted (i) to develop a near infrared reflectance spectroscopy (NIRS) based method to estimate the legume content in multispecies legume–grass mixtures as in widespread use in Western Europe, (ii) to compare end‐points and artificial mixture calibration strategies and (iii) to evaluate the effect grinding may have on the NIRS predictions of legume content. Calibration samples were taken in 1999 and 2000 in legume–grass fields that comprised a broad variation of site conditions. The samples were hand‐sorted, dried, and ground. End‐points calibrations derived from sets of legume samples (=100% legume content) and sets of grass samples (=0% legume content) were compared with calibrations where 63 spectra of artificially mixed samples (increments of 5% legume content) were added to represent a continuum of possible values of legume content. The influence of the preparation protocol of defined dry mixtures was compared by preparing duplicate mixtures where one replicate was prepared from fresh material, dried, and ground as a mixture and the other mixed from dry, ground material. Log (1/R) (R = reflectance) spectra were taken of all samples. Partial least squares regression was applied to develop calibration algorithms in the spectral range of 7500 to 3950 cm−1 (1333–2532 nm). First derivative combined with vector normalization proved to be the best data pretreatment. For each strategy, three models were developed: One model was based on all samples validated with a one‐leave‐out cross‐validation, and two models were based on half of the samples validated by the other half. Prediction errors were between 2.2 and 4.0%, and coefficients of determination of all validations were greater than 99% so that no remarkable differences between the models existed. At least 70% of the selected spectral regions were in common for all models. These regions do not describe legumes themselves but rather the information that discriminates them from grasses. It is emphasized that the calibrations introduced have the potential for a broad use that needs to be proved by further validations.
Maize Radiation Use Efficiency under Optimal Growth Conditions
Authors: Lindquist John L. , Arkebauer Timothy J. , Walters Daniel T. , Cassman Kenneth G. , Dobermann Achim
Published: July 2010

Accurate measurement of crop growth and radiation use efficiency (RUE) under optimal growth conditions is required to predict plant dry matter accumulation and grain yield near the genetic growth potential. Research was conducted to quantify the biomass and leaf area index (LAI) accumulation, extinction coefficient, and RUE of maize (Zea mays L.) under conditions of optimal growth. Maize was grown in two environments over five growing seasons (1998–2002). Total aboveground biomass at maturity ranged from 2257 g m−2 in 1998 to 2916 g m−2 in 2001; values that are considerably greater than the biomass achieved in most previous studies on RUE in maize. Peak LAI ranged from 4.8 to 7.8. Maize extinction coefficients during vegetative growth (k) were within the range of recently published values (0.49 ± 0.03), with no clear pattern of differences in k among years. Seasonal changes in interception of photosynthetically active radiation (PAR) were similar across all but one year. Estimates of RUE were obtained using the short‐interval crop growth rate method and the cumulative biomass and absorbed PAR (APAR) method. Values of RUE obtained using the two methods were 3.74 (±0.20) g MJ−1 APAR and 3.84 (±0.08) g MJ−1 APAR, respectively, and did not vary among years. This compares to a published mean RUE for maize of 3.3 g MJ−1 of intercepted PAR (Mitchell et al., 1998). Moreover, RUE did not decline during grain filling. Differences in biomass accumulation among years were attributed in part to differences in observed radiation interception, which varied primarily due to differences in LAI. Maize simulation models that rely on RUE for biomass accumulation should use an RUE of 3.8 g MJ−1 APAR for predicting optimum yields without growth limitations.
Spatial and Temporal Variation of Energy and Carbon Fluxes in Central Iowa
Authors: Hatfield J. L. , Prueger J. H. , Kustas W. P.
Published: July 2010

Energy balance and CO2 exchange of agricultural crops has been investigated through limited field studies because of the expense of the monitoring equipment and availability of fields to place equipment. Quantifying the spatial and temporal variation in the energy balance and CO2 dynamics over crop canopies will improve regional‐scale estimates of water and C fluxes. A study was conducted in central Iowa during 2002 as part of the Soil Moisture Experiment to evaluate soil moisture energy exchange across an intensive corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] production area near Ames, IA (lat. 41.98380985, long. −93.75497316). Surface energy balance and CO2 flux stations were placed in 12 corn and soybean fields across different soils and landscapes in and around the Walnut Creek watershed. Variability among fields was induced by three factors. Within a day, variations among fields were due to the presence of cumulus cloud formation in the afternoon. Short‐term differences across days among the fields were due to variation in the spatial pattern of rainfall events causing differential drying. Throughout the season, differences among fields were due to soil water availability, which affected crop growth and ground cover. Differences in early season ground cover were correlated with energy balance (r = 0.80). During the growing season, latent heat and CO2 uptake were closely related (r = 0.85). Characterization of the spatial distribution of energy balance and CO2 uptake in an intensive cropping region provides guidance on the confidence that can be placed in interpreting single‐site measurements.
Mixtures of Kura Clover with Small Grains or Italian Ryegrass to Extend the Forage Production Season in the Northern USA
Authors: Contreras‐Govea Francisco E. , Albrecht Kenneth A.
Published: July 2010

Kura clover (Trifolium ambiguum M. Bieb.) has demonstrated excellent persistence in the northern USA but initiates dormancy earlier in autumn and breaks dormancy later in spring than other adapted legumes. The objective of this study was to determine if combinations of kura clover and small grains or ryegrass (Lolium multiflorum Lam.) could extend the production season for high quality forage in autumn and spring. The study was conducted from 1998 to 2000 in Arlington and Lancaster, WI. Oat (Avena sativa L.), barley (Hordeum vulgare L.), winter wheat (Triticum aestivum L.), winter rye (Secale cereale L.), and Italian ryegrass, were sown in August in monoculture and in binary mixtures with previously established kura clover. In autumn, monoculture kura clover and all mixtures had similar forage yield, but 1.5 Mg ha−1 lower yield than monoculture oat. In spring, binary mixtures of kura clover with winter wheat or winter rye yielded 0.88 Mg ha−1 more than monoculture kura clover. In spring, mixtures with winter wheat or winter rye contained about 60% kura clover. Binary mixtures and monoculture kura clover had 35% greater crude protein, similar in vitro true digestibility, and 32% lower neutral detergent fiber than monoculture small grains and ryegrass in autumn and spring. Oat, barley, or ryegrass sown into kura clover in autumn provide no yield advantage over monoculture kura clover. Winter small grains sown into kura clover in autumn increased forage yield in early spring, but had no impact on full‐season production compared with monoculture kura clover. Ryegrass did not affect spring yield, but did increase full‐season production by 15% compared with monoculture kura clover. Winter small grains and ryegrass can successfully be sown into monoculture kura clover in autumn without the use of herbicides and can increase early spring or total season forage production the following year.
Nitrogen Uptake across Site Specific Management Zones in Irrigated Corn Production Systems
Authors: Inman D. , Khosla R. , Westfall D. G. , Reich R.
Published: July 2010

Development of improved fertilizer management practices has the potential to increase fertilizer use efficiency and improve environmental quality. The objectives of this study were (i) to characterize the within field spatial variability of N uptake across irrigated corn production fields, (ii) to quantify and compare N uptake and grain yield across three site specific management zones (SSMZs), and (iii) to compare grain yield response to applied N between management zones. This study was conducted on continuous corn (Zea mays L.) in irrigated fields in northeastern Colorado. Fields were classified into high, medium, and low site specific management zones. Treatments consisted of a control and two uniform N application rates over 2 site‐years (one field over 2 consecutive yr and another field over 1 yr). Nitrogen fertilizer rates varied with site‐year and ranged from 56 to 268 kg N ha−1. Aboveground biomass samples were collected at physiological maturity and analyzed for total N. Between management zones, N uptake, grain yield, and grain yield response to applied N were found to be statistically different (p < 0.05). Management zones were found to be less spatially variable than the whole field. The SSMZs accurately characterized variability in N uptake as well as grain yield response to applied N. Thus, variation in N uptake and grain yield can potentially be managed using SSMZs.
‘SeaIsle 2000’ Paspalum Putting Surface Response to Mowing Height and Nitrogen Fertilizer
Authors: Kopec David M. , Walworth James L. , Gilbert Jeffrey J. , Sower Gregory M. , Pessarakli Mohammad
Published: July 2010

‘SeaIsle 2000’ seashore paspalum (Paspalum vaginatum Sw.), when maintained as a putting green surface, was observed for turfgrass response attributes, nutrient content, and ball roll distance (BRD) when subjected to three mowing heights and four monthly N application rates during a 2‐yr period. Acceptable visible turfgrass quality of 6.0 (on a scale of 1 to 9) or greater was achieved at all mowing heights and with all N application rates. Shoot counts were greatest in both years at the 0.3‐cm height and were not influenced by N. Root weights were not affected by mowing height or applied N fertilizer rates. Clipping dry weight generally increased with shorter mowing height and higher levels of applied N. There was a trend for leaf Fe levels to decrease with increasing mowing height. Leaf tissue N increased in response to increasing levels of N application. The BRD was largely unaffected by N fertilization, but was consistently affected by mowing height and rolling. Mowing height significantly affected BRD values on seven of eight test dates in 2000 and on all 12 in 2001, with greatest BRD occurring at the shortest mowing height. The maximum observed BRD was 277 cm. Mean BRD on rolled and unrolled turf surfaces mowed at the 0.3‐cm height were 234 and 214 cm, respectively.
Effect of Zinc Source and Application Time on Zinc Uptake and Grain Yield of Flood‐Irrigated Rice
Authors: Slaton Nathan A. , Norman Richard J. , Wilson Charles E.
Published: July 2010

Zinc is the most common micronutrient fertilizer applied to rice (Oryza sativa L.) in the USA. Preventing yield limitations from Zn deficiency requires knowledge of the proper application rates and times of commercial Zn fertilizers. The objective of this research was to evaluate the Zn nutrition and grain yield response of rice as affected by Zn‐fertilizer source and application time. Four field trials were conducted to evaluate several Zn sources applied preplant incorporated (PPI), delayed preemergence (DPRE), and postemergence (POST) before flooding at the four‐leaf stage. Zinc treatments included Zn solutions sprayed at 1.1 to 2.2 kg Zn ha−1 and dry‐granular Zn fertilizers broadcast at 11.2 kg Zn ha−1. Zinc‐fertilizer source, averaged across application times, significantly affected grain yield at all sites with Zn fertilization increasing yields by 12 to 180% compared with the unfertilized control. Zinc‐application time, averaged across Zn sources, significantly affected grain yield at only one site, which had severe Zn deficiency. Zinc applied PPI (6915 kg grain ha−1) and DPRE (7456 kg grain ha−1) produced similar yields that were greater than Zn applied POST (5526 kg grain ha−1). Zinc solutions sprayed at 1.1 to 2.2 kg Zn ha−1 generally produced yields that were comparable with yields from granular fertilizers applied at 11.2 kg Zn ha−1. Fertilization recommendations should reflect the advantages of Zn fertilization performed before crop emergence. Growers can confidently apply Zn fertilizer solutions or granules to the soil surface without incorporation before emergence, with recommended rates (11 kg Zn ha−1) of granular Zn preferred for alkaline, Zn‐deficient soils.
Cotton in Ultra‐Narrow Row Spacing: Plant Density and Nitrogen Fertilizer Rates
Authors: Boquet Donald J.
Published: July 2010

Ultra‐narrow row spacing (UNR) of 25 cm or less may be a viable alternative to wide‐row spacing for cotton (Gossypium hirsutum L.) in the Mid‐South USA but yield and quality in relation to wide‐row cotton have been variable. Field experiments were conducted from 1997 through 2000 on Gigger silt loam (fine‐silty, mixed, thermic Typic Fragiudalfs) to: (i) determine the effects of plant density (128000, 256000, and 385000 plants ha−1) and N rate (90, 112, 134, and 157 kg ha−1) on irrigated and rain‐fed UNR cotton and (ii) compare performance of UNR cotton to wide‐row cotton (102‐cm row spacing) at a density of 116000 plants ha−1 and fertilized with 90 kg N ha−1. Increase in plant density decreased lint yield of irrigated cotton and had no effect on yield of rain‐fed cotton. Increase in plant density of irrigated cotton decreased boll number plant−1 and individual boll weight but had no effect on boll number m−2. Yield components of rain‐fed cotton were not affected by varying plant density. Increasing N rate did not affect yield or yield components of irrigated or rain‐fed cotton. Plant density, N rate, and row spacing affected fiber properties but effects were small and would not affect value or utilization. Under irrigation, UNR cotton averaged 771 kg lint ha−1 and wide‐row cotton averaged 1069 kg lint ha−1. Without irrigation, UNR cotton averaged 377 kg lint ha−1 and wide‐row cotton averaged 586 kg lint ha−1. Maximum yields of UNR cotton were attained from plant densities in the range of 128000 to 256000 ha−1 and a N rate of 90 kg ha−1
Challenging Approaches to Nitrogen Fertilizer Recommendations in Continuous Cropping Systems in the Great Plains
Authors: Schlegel Alan J. , Grant Cynthia A. , Havlin John L.
Published: July 2010

Cropping systems in the Great Plains have evolved over the past two decades from reliance on summer fallowing to continuous cropping under reduced or no‐tillage. Most N recommendation models were developed in fallow systems under conventional tillage and were based on average yield goal, with adjustments for soil profile N content. The objective of this review is to examine the impact of continuous cropping on N requirements. With high‐residue continuous cropping systems, N requirements may increase because of increased annualized production, reduced contribution of N mineralization, and increased immobilization and volatilization potential of surface‐applied fertilizer N. Mitigating these effects on N availability and supplemental N requirements are the reduction in yield per crop, reduced nitrate (NO3) leaching potential, increased N use efficiency (NUE), and increased rates of N mineralization due to higher soil organic matter (OM) content. Unfortunately, increased year‐to‐year yield variability with continuous cropping increases the difficulty in accurately estimating yield goals. Also, reducing the frequency and duration of fallow may reduce the usefulness of the preplant soil N tests in estimating N availability. Recent research has evaluated the use of optical sensors during the growing season to assess N stress and to estimate crop N requirements. If proved feasible for many crops, this would provide a drastic change for determining N recommendations. In the absence of a reasonable yield goal and known residual soil N content, a fertilizer N rate near 70 kg N ha−1 or less was generally sufficient to optimize small‐grain or oilseed yields in several continuous cropping studies.
Long‐Term Evaluation of Poultry Litter as a Source of Nitrogen for Cotton and Corn
Authors: Mitchell Charles C. , Tu Shuxin
Published: July 2010

Land application of poultry broiler litter (BL) in agricultural production is a widely used practice. However, cotton (Gossypium hirsutum L.) growers in poultry‐producing regions of the southern USA have been reluctant to use BL as a crop nutrient source. Field experiments were conducted for 13 yr to study the effect of BL application to cotton and corn (Zea mays L.) under conventional and conservation tillage systems. Nitrogen rates from 0 to 269 kg ha−1 were applied annually at two locations to compare the effect of BL and ammonium nitrate (AN) as N sources. The relationship between the total N rates (N) applied and the relative N availability (y) based on the crop yield by application of BL and AN is described by linear equation: y = 71.58 + 0.15N (r = 0.66). In most years, there were no differences in relative yields from total N applied as BL or AN. The amplitude of yield increase based on N source varied with rainfall during the growing season. The residual effect of BL in the second year after application resulted in 30 to 50% of the cotton lint yield and 25 to 65% of the corn grain yield that resulted from a standard N fertilization rate. General observations suggest that N availability from BL is similar whether surface‐applied as in conservation tillage systems or incorporated as in conventionally tilled systems.
Effects of Swine Lagoon Effluent Relative to Commercial Fertilizer Applications on Warm‐Season Forage Nutritive Value
Authors: Adeli A. , Varco J. J. , Sistani K. R. , Rowe D. E.
Published: July 2010

Two field experiments were conducted to evaluate the effects of comparable rates of swine lagoon effluent and commercial fertilizer at different harvest dates on dry matter yield and nutritive value of bermudagrass (Cynodon dactylon L.) grown on an acid Vaiden silty clay (very fine, montmorillonitic, thermic, Vertic Hapludalf) and johnsongrass (Sorghum halepense L.) grown on an alkaline Okolona silty clay (fine, montmorillonitic, therimic, Typic Chromudert). At each site, a randomized complete block design with a factorial arrangement of treatments replicated four times was used. Treatments were multiple effluent irrigations resulting in four N rates from 0 to 665 kg N ha−1 yr−1. In each block, commercial fertilizer (N, P, and K) treatments were applied to additional plots at rates equivalent to swine effluent rates. Total dry matter yield and crude protein (CP) for bermudagrass and johnsongrass reached a plateau with application of approximately 450 kg N ha−1 from either swine effluent or commercial fertilizer. Neutral detergent fiber (NDF) and acid detergent fiber (ADF) peaked at the low fertilization rate and then declined with increasing effluent and commercial fertilizer rates. An inverse relationship was obtained for in vitro true digestibility (IVTD) in response to fertilization rate for both grasses. Forage dry matter, CP, NDF, and ADF levels peaked in the July harvest and then declined, but forage IVTD level declined in July harvest. Only in July 1996, forage NO3–N concentration was lower for swine effluent than commercial fertilizer. Swine effluent and commercial fertilizer had similar effects on forage dry matter yield and nutritive value.
Conservation Tillage and Herbicide Management for Two Peanut Cultivars
Authors: Tubbs R. Scott , Gallaher Raymond N.
Published: July 2010

To reduce production costs and soil erosion and aid in management of tomato spotted wilt tospovirus (TSWV), many peanut (Arachis hypogaea L.) farmers in Florida are converting to conservation tillage systems. A split‐split plot experiment with six replications was conducted over 2 yr to evaluate pod yield and grass control from five tillage systems, two peanut cultivars (‘Georgia Green’ and ‘Andru 93’), and two postemergence herbicide programs (paraquat plus acifluorfen plus bentazon and imazapic). Peanut planted into rye (Secale cereale L.) with strip‐till management yielded (5280 to 5480 kg ha−1) similar to those in conventional tillage (5140 kg ha−1). Georgia Green (5500 kg ha−1) yielded higher than Andru 93 (5100 kg ha−1). Yields were greater for paraquat plus acifluorfen plus bentazon than for imazapic in 1999, but gross value was equivalent. Yields and gross value were higher for imazapic in 2000. Grass weeds included fall panicum (Panicum dichotomiflorum Michx.), Texas panicum (Panicum texanum L.), and large crabgrass [Digitaria sanguinalis (L.) Scop.], which were controlled more effectively with imazapic both years (18% greater control in 1999 and 52% greater control in 2000). The difference in yields between herbicide treatments for the 2 yr is attributed to replanting and drastically lower levels of grass control in 2000. These results support the claim that reduced tillage systems, with proper cultivar and herbicide selection, provide advantages over conventional tillage systems.
Biomass Yield, Phenology, and Survival of Diverse Switchgrass Cultivars and Experimental Strains in Western North Dakota
Authors: Berdahl J. D. , Frank A. B. , Krupinsky J. M. , Carr P. M. , Hanson J. D. , Johnson H. A.
Published: July 2010

Switchgrass (Panicum virgatum L.) has been identified as a potential biofuel crop for the northern Great Plains region of the USA. Biomass yield and survival percentage in western North Dakota were measured for 3 yr at three field sites, and plant development was monitored for 2 yr at one site to determine adaptation and stability of performance for eight diverse switchgrass cultivars and experimental strains. Harvest treatments were single annual cuttings in mid‐August or mid‐September. Except for ‘Dacotah’, ND3743, and ‘Sunburst’, all other entries originated greater than 500 km south of the evaluation sites and were subject to winter injury. Sunburst, from southern South Dakota, ranked first or second in biomass yield in all environments and was the top‐yielding entry in all environments in the third production year, a drought year at all sites. ‘Trailblazer’ ranked first, second, or third in biomass yield in all environments while yield ranking of the other entries was not consistent. Genotype × environment interactions occurred for biomass yield and would be expected based on the wide range in origin among the eight populations. Survival percentage was equal for the two harvest dates, but all eight populations averaged greater biomass yields at the mid‐September (5.98 Mg ha−1) than the mid‐August (5.51 Mg ha−1) harvest. Biomass yield of Sunburst at the site with the greatest yield potential ranged from 3.20 Mg ha−1 in a drought year to 12.48 Mg ha−1 in a year with above‐average precipitation. Biomass yield of adapted switchgrass cultivars fluctuated widely in western North Dakota, depending in large part on available soil water.
Integrating Cotton and Beef Production to Reduce Water Withdrawal from the Ogallala Aquifer in the Southern High Plains
Authors: Allen V. G. , Brown C. P. , Kellison R. , Segarra E. , Wheeler T. , Dotray P. A. , Conkwright J. C. , Green C. J. , Acosta‐Martinez V.
Published: July 2010

Agriculture in the Texas High Plains depends heavily on irrigation with water withdrawn from the Ogallala aquifer at nonsustainable rates. Our hypothesis was that integrating crop and livestock systems would reduce irrigation water use, maintain profitability, and diversify income compared with a cotton (Gossypium hirsutum L.) monoculture. Thus, from 1998 to 2002, two large‐scale systems, with three replications in a randomized block design, compared water use, productivity, and economics of (i) a cotton (var ‘Paymaster 2326RR’) monoculture with terminated wheat (Triticum aestivum L.) and (ii) an integrated three‐paddock system that included cotton in a two‐paddock rotation with grazed wheat and rye (Secale cereale L.) and the perennial ‘WW‐B. Dahl’ old world bluestem [Bothriochloa bladhii (Retz) S.T. Blake] for grazing and seed production. All paddocks were irrigated by subsurface drip. Angus crossbred beef steers (Bos taurus L.; initial body weight = 249 kg; standard deviation = 26 kg) grazed from January to mid‐July. During the 4 yr of this experiment following the establishment year, cotton lint yield was 1036 and 1062 kg ha−1 for the cotton monoculture and the integrated system, respectively. Bluestem seed yield averaged 24 kg pure live seed ha−1. Steers gained 153 kg on pasture and 0.82 kg d−1. Per hectare, the integrated system used 23% less (P < 0.001) irrigation water, 40% less N fertilizer, and fewer other chemical inputs than the cotton monoculture. Profitability was about 90% greater for the integrated system at described conditions. Integrated production systems that are less dependent on irrigation and chemical inputs appear possible while improving profitability.
MEASUREMENT AND PARTITIONING OF IN SITU CARBON DIOXIDE FLUXES IN TURFGRASSES USING A PRESSURIZED CHAMBER
Authors: Bremer Dale J. , Ham Jay M.
Published: July 2010

Field measurements of photosynthesis in turfgrass often are conducted with hand‐held chambers that are temporarily placed over the canopy and soil. Because gas exchange measurements include soil respiration (R
s), results do not represent net canopy photosynthesis (Pc,net) but rather net ecosystem exchange of CO2 (NEE) or gross canopy photosynthesis (Pg) less the sum of canopy respiration (Rc) and Rs. Chambers attached to steady‐state, portable photosynthesis systems normally are partially pressurized, which may partially suppress Rs (depending on pressure magnitude and soil moisture and type) and may overestimate NEE. Objectives of this research were to: (i) develop a chamber in which pressure could be manipulated, (ii) measure CO2 fluxes at neutral pressure (chamber pressure equals atmospheric) to estimate NEE; (iii) measure Pc,net by applying increasing pressure until Rs is prevented from entering the chamber, and (iv) partition CO2 fluxes among Pg, Rc, and Rs. Pressure fluctuations of ±1.0 Pa were uncontrollable, which caused large differences in CO2 exchanges near neutral pressure and prevented measurements of NEE. Chamber pressurization from 50 to 200 Pa suppressed most but not all Rs, which disallowed measurement of Pc,net using a single pressurized reading. A new procedure provided estimates of Pc,net, Rc, and Pg from pressurized measurements of turf under sunlit and shaded conditions and from turf clipped at ground level. Flux from clipped plots under pressurization provided estimates of Rs that could not be suppressed with pressure. This was subtracted from pressurized readings over sunlit and shaded unclipped canopies to estimate Pc,net and Rc, respectively.
Structural Composition, Growth Stage, and Cultivar Affects on Kentucky Bluegrass Forage Yield and Nutrient Composition
Authors: Holman Johnathon D. , Hunt Carl , Thill Donn
Published: July 2010

Kentucky bluegrass (Poa pratensis L.) is an important turf and forage grass, yet there is little information on its forage yield and nutrient composition. This study evaluated the effect of Kentucky bluegrass cultivar (Ascot, Kenblue, Limousine, and Touchdown), growth stage (boot, anthesis, and seed ripening), and structural composition (percentage head, leaf, and stem) on forage yield and nutrient composition. Nutrient composition measurements included dry matter, crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), lignin, and 48‐h in vitro true digestibility (IVTD). Tall cultivars had the greatest yield, and yield tended to be greatest at seed ripening. Structural composition varied among cultivars due to differences in cultivar height and yield. Nutrient composition was not different among cultivars despite differences in structural composition among cultivars and nutrient composition differences among structural components. Leaves were greatest in IVTD (636 g kg−1), stems were greatest in NDF (740 g kg−1) and ADF (430 g kg−1), and lowest in CP (30 g kg−1) and IVTD (455 g kg−1), and heads were lowest in ADF (269 g kg−1) and greatest in lignin (83 g kg−1). Nutrient level was greatest at boot and averaged 435 g kg−1 NDF, 197 g kg−1 ADF, 17 g kg−1 lignin, 165 g kg−1 CP, and 766 g kg−1 IVTD. On average between boot and anthesis, CP decreased 0.57% d−1 in 2003 and 0.21% d−1 in 2004, and IVTD declined 0.47% d−1 in 2003 and 0.49% d−1 in 2004. Nutrient level decreased as the stand aged due to an increase in structural carbohydrates and a decrease in IVTD.
Estimating Grain and Straw Nitrogen Concentration in Grain Crops Based on Aboveground Nitrogen Concentration and Harvest Index
Authors: Kemanian Armen R. , Stöckle Claudio O. , Huggins David R.
Published: July 2010

Simulating grain (Ng) and straw (Ns) 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 (Nt) 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 Ng the relative RMSE ranged from 3 to 10% (five experiments) and was 31% in one experiment in which the estimated Ng 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 Ng within a species and if the method can be applied to legume crops.
Nutrient Management Behavior on Wisconsin Dairy Farms
Authors: Powell J. M. , Jackson‐Smith D. B. , McCrory D. F. , Saam H. , Mariola M.
Published: July 2010

Nutrient management plans for livestock operations should account for rates and timing of manure application to cropland, as well as how manure is integrated with other nutrient sources. Little is known, however, about actual nutrient management behavior of farmers, and what changes may be needed for farmers to adhere to nutrient management regulations. Detailed records were kept on fertilizer, manure, and legume N and P applications on 33 representative Wisconsin dairy farms during the period October 2003 through September 2004. Average available N applications ranged from 118 to 200 kg ha−1 of which 40% was derived from fertilizer, 30% from manure and 30% from previous legume. On a regional basis, the following percentages of corn (Zea mays L.) area fell within available N application categories of 0, 1 to 80, 81 to 160, 161 to 240 and >240 kg ha−1, respectively: in the Northeast (NE) region, <1, 26, 33, 21, and 19% of the total corn area surveyed (504 ha); in the South–Central (SC) region, <1, 39, 41, 14, and 5% of the corn area (576 ha); and in the Southwest (SW) region, 0, 31, 45, 14, and 10% of the corn area (180 ha). Average available P applications ranged from 16 to 18 kg ha−1, of which 65% came from manure and 35% from fertilizer. On a regional basis, the following percentages of surveyed cropland area fell within available P application categories of 0, 1 to 24, 25 to 48, 49 to 72 and >72 kg ha−1, respectively: in the NE region, 30, 50, 15, 4, and 1% of the cropland area (1340 ha); in the SC region, 23, 54, 17, 5, and 1% of the cropland area (1168 ha); and in the SW region, 41, 48, 8, 1, and 2% of the cropland area (542 ha). Of the total cropland area (ha) across all regions that received manure during winter, 7 to 25% were within regulated surface water buffer zones. In the NE, SC, and SW regions, 100, 83, and 63% of winter‐spread cropland area received available P application rates <24 kg ha−1, the 1‐yr crop P replacement ceiling set by State regulations. Regional differences in nutrient management behavior due to topography, soils and other factors should be used to better target efforts aimed at improving fertilizer‐manure‐legume management on Wisconsin dairy farms.
Tillage and Compost Effects on Corn Growth, Nutrient Accumulation, and Grain Yield
Authors: Singer Jeremy W. , Logsdon Sally D. , Meek David W.
Published: July 2010

Applying organic amendments to cropland affects corn (Zea mays L.) response to tillage systems differently. Identifying causes of the tillage by amendment interaction could match amendment inputs to responsive tillage systems. The objectives of this research were to determine if shoot dry matter (DM), nutrient uptake, and soil water use could explain the tillage by compost interaction for corn–grain yield. A corn–soybean [Glycine max (L.) Merr.]–wheat (Triticum aestivum L.)/clover (Trifolium spp.) rotation, in all phases, with or without compost amendment, was initiated in 1998 in plots that had been managed with moldboard plow (MP), chisel plow (CT), or no‐tillage (NT) since 1988. Compost amendment increased corn whole‐plant P and K uptake 19 and 21%, averaged across 2 yr. No‐tillage increased whole‐plant P uptake 1 yr compared to MP and CT (113 vs. 65 kg ha−1) and increased grain P concentration (3.1 vs. 1.5 g kg−1). Compost provided no benefit (2 yr) or a negative effect (1 yr, 22%) to corn yield in MP. Compost provided no benefit to corn yield in CT. Corn growing in NT derived no benefit (2 yr) or a positive (1 yr, 9%) effect on grain yield from compost amendment. The tillage and compost responses observed in this study cannot be explained by plant N, soil water use, leaf gas exchange, or DM partitioning. Grain yield from soil managed using NT may respond to compost amendment, but reasons for this response remain unclear.
Allelopathic Potential of Various Plant Species on Downy Brome: Implications for Weed Control in Wheat Production
Authors: Machado Stephen
Published: July 2010

Allelopathy, the ability of plants to inhibit germination of other plants, is an untapped resource for weed control in crops that could revolutionize organic crop production. The main objective of the study was to evaluate allelopathic potential of various plant species on downy brome (Bromus tectorum L.), a major pest of wheat (Triticum aestivum L.). To screen for potential allelopathy, plants were grown to flowering stage in a greenhouse, separated into shoots and roots, dried, and ground. Five percent aqueous extracts (w/v) were prepared by extracting 5 g of dried, ground plant samples with 100 mL of deionized water. Downy brome seeds were germinated on extract‐amended sand. Extracts from most plant species tested inhibited downy brome and wheat seed germination. Extracts from broadleaf plants were more inhibitory than extracts from cereal plants. In most plant species, shoot extracts were more inhibitory to growth of the root and shoot of downy brome than root extracts. Meadowfoam seed meal (Limnanthes alba Hartw.), yard‐long bean [Vigna sesquipedalis (L.) Fruw.], blue spruce (Picea pungens pungens Engelm), and pine (Pinus spp.) extracts, which completely inhibited the germination of downy brome seed, have the potential for use in the control of downy brome in wheat‐based cropping systems. Meadowfoam seed meal extract inhibited wheat germination by 77% and root and shoot growth by 97 and 96%, respectively. Radishes reduced wheat germination by 75 to 100%, root growth by 54 to 80% and shoot growth by 45 to 81%. Plants evaluated in this study have the potential to be used for biologically based weed control methods in organic cropping systems.
Influence of Nitrogen Rate and Form on Quality of Putting Greens Cohabited by Creeping Bentgrass and Annual Bluegrass
Authors: Schlossberg Maxim J. , Schmidt John P.
Published: July 2010

Of the essential nutrients, N fertility generally influences golf course putting green (PG) quality and growth rate most significantly. Despite considerable field research on N fertility of PGs, results interpretation and transfer to practice is complicated by various influential factors; including unrepresentative mowing heights and/or frequency, varying irrigation water quality, undeclared composition of mixed swards, withdrawn cultivars, and/or use of temperature‐dependent organic fertilizer sources. A 2‐yr field study was initiated in 2003 at University Park, PA, to evaluate the influence of soluble N fertilizer source and rate on qualitative and nutritional parameters of a mature, primarily surface‐drained, “push‐up” PG cohabited by ‘Penn A4’ creeping bentgrass (Agrostis palustris Huds.) and annual bluegrass (Poa annua L.). Using an array of soluble N form quotients (NH4–N/NO3–N), split applications of annual N fertilizer rates ranging from 69 to 402 kg ha−1 were sprayed every 15 ± 4 d, April to October. Putting green growth, color, N uptake (NUP), and leaf N, K, Ca, Mn, Cu, and Zn increased directly with N rate, while plots receiving N rates in excess of 244 kg ha−1 yr−1 demonstrated acceptable PG quality and tissue nutrient concentrations. However, N rates >244 kg ha−1 yr−1 containing >50% NH4–N significantly enhanced shoot growth, color, NUP, leaf Mn, P, and Mg levels, when compared to equal rates containing ≥50% NO3–N. Frequent fertilization with NH4–N at annual rates >244 kg ha−1 maximized canopy color and most tissue nutrient levels of a mature creeping bentgrass/annual bluegrass cohabited PG growing on a neutral, fine‐textured soil.