bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tiller Demographics and Leaf Area Index of Four Perennial Pasture Grasses
Authors: Mitchell Robert B. , Moser Lowell E. , Moore Kenneth J. , Redfearn Daren D. 
Published: July 2010

AbstractDeveloping grazing systems requires basic information on the growth and development of adapted species. The objective of this field study was to determine seasonal tiller demographics and leaf area index (LAI) of intermediate wheatgrass [Thinopyrum intermedium (Host) Barkw. & D.R. Dewey], smooth bromegrass (Bromus inermis Leyss.), switchgrass (Panicum virgatum L.), and big bluestem (Andropogon gerardii Vitman) tiller populations. This study was conducted in 1992 and 1993 near Mead, NE, on a silty clay loam soil (Typic Argiudoll) as a randomized complete block. Monocultures were harvested six times each year for tiller demographics. Additionally, mean stage count (MSC), a quantified estimate of tiller population maturity, was determined at each harvest. The LAI was indirectly measured using a canopy analyzer at 7‐ to 14‐d intervals. Tiller density for all species generally declined as MSC increased. Tiller demographics were highly variable by year for intermediate wheatgrass and smooth bromegrass, which indicates that grazing management should be based on current tiller populations. Density of vegetative tillers declined most rapidly for smooth bromegrass, followed by intermediate wheatgrass, switchgrass, and big bluestem. Switchgrass and big bluestem tiller demographics were more uniform and predictable across years than intermediate wheatgrass and smooth bromegrass. The LAI for all species increased as MSC increased. Maximum LAI for intermediate wheatgrass, smooth bromegrass, switchgrass, and big bluestem in 1992 was 4.7, 5.1, 4.9, and 5.8, respectively. Integrating tiller demographics and LAI suggests that initial grazing readiness starts with smooth bromegrass in early spring, followed by intermediate wheatgrass in about 2 wk, switchgrass in late spring, and big bluestem in early summer.
Dry Matter Accumulation and Dinitrogen Fixation of Annual Medicago Species
Authors: Zhu Yanping , Sheaffer Craig C. , Russelle Michael P. , Vance Carroll P. 
Published: July 2010

AbstractAssessment of the N2 fixation potential of annual medics (Medicago spp.) in the upper Midwest is important for predicting the net N contribution to cropping systems. Our objectives were to determine the dry matter (DM) accumulation pattern of herbage, roots, and nodules of several annual medic species used as summer annuals and to measure the percentage and amount of N derived from N2 fixation by annual medics using isotope dilution and difference methods. Experiments were conducted on a Hubbard loamy sand (Udorthentic Haploboroll) at Becker, MN, and a Tallula silt loam (Typic Hapludoll) at Rosemount, MN. The experimental design at both locations was a randomized complete block with six replicates. Medicago truncatula Gaertn., M. polymorpha L., M. scutellata (L.) Mill., and M. rugosa Desr. were inoculated with commercial rhizobial inoculant and were seeded in late May. Herbage, root, and nodule DM of N2‐fixing annual medics continued to increase until about 72 d after planting (DAP). The highest maximum herbage, root, and nodule DM yields were 10 669, 648, and 169 kg ha−1, respectively, from M. polymorpha in 1993. Based on the estimate from the isotope dilution (ID) method, herbage of annual medics at maximum DM accumulation contained 86% N derived from atmosphere (%Ndfa), using ryegrass (Lolium multiflorum Lam.) as a reference crop, or 79% Ndfa, using noninoculated M. rugosa as a reference crop. The amount of Ndfa in annual medic herbage ranged from 100 to 200 kg ha2212;1 based on estimates using either the ID method or the difference method (D‐method), with M. polymorpha producing the highest and M. rugosa producing the lowest amount. Estimates of Ndfa from the ID and D‐methods were strongly correlated. We conclude that annual medics have the potential to contribute a significant amount of N to cropping systems when seeded in the spring and harvested or incorporated into the soil 2 to 3 mo. later.
Soil Carbon Pools under Conventional and No‐Tillage Systems in the Argentine Rolling Pampa
Authors: Alvarez Roberto , Russo Miguel E. , Prystupa Pablo , Scheiner Javier D. , Blotta Luis 
Published: July 2010

AbstractThe Rolling Pampa is the most important cropping region of Argentina, and its soils are subjected to degradation. No‐tillage has been proposed to replace the use of the moldboard plow to reduce soil C losses. The effects of no‐tillage and plow tillage with and without N fertilization (0 or 90 kg N ha−1) on C inputs and outputs of a Typic Argiudoll and on organic C level and density fractions were studied in a field experiment at the end of 15 yr under a corn (Zea mays L.)‐wheat (Triticum aestivum L.)‐soybean [Glycine max (L.) Merr.] rotation. Microbial biomass and the rate of organic C mineralization during laboratory incubations were also determined. Nitrogen fertilization had no significant influence on C emission in the field, soil organic matter level or microbial biomass and activity. The annual C budget was negative under both tillage systems, but no‐tillage lost about 0.7 to 1.5 Mg ha−1 yr−1 more C than did plow tillage. Carbon in the medium‐density fraction (density = 1.6‐2.0 g mL−1) of the 0‐ to 20‐cm soil layer was 30% higher (P ≤ 0.05) under no‐tillage. Light (density < 1.6 g mL−1) and heavy (density > 2.0 g mL−1) organic fractions, total C, and microbial biomass and activity in the 0‐ to 20‐ cm layer were not different in no‐tilled and plowed soils, despite different patterns of distribution with depth. The rates of organic C mineralization during laboratory incubations were the same for both tillage systems. We propose that, after an accumulation phase, soil under no‐tillage loses higher amounts of CO2‐C than under plowing. The use of no‐tillage would not significantly affect soil organic matter pools of the region in situations with low erosion losses.
Optimum Transplanting Dates for Rice in Kerala, India, Determined Using Both CERES v3.0 and ClimProb
Authors: Saseendran Saseendran A. , Hubbard Kenneth G. , Singh Kamalesh K. , Mendiratta Nisha , Rathore Laxman S. , Singh Shyam V. 
Published: July 2010

AbstractRice (Oryza sativa L.) is an important food crop for more than half the world's population. It grows best under shallow flooded conditions. For establishing a healthy rice stand in a flooded field, the seedlings of the crop are first grown in nurseries and then transplanted into the field. At a specific location, transplanting dates determine how growing conditions later in the season will affect the rice crop. Dry conditions after ripening, favorable to maintaining the quality of rice through harvest, may be more or less likely to occur, depending on the transplanting date selected. The objective of this study was to determine optimum transplanting dates for rice at five locations in Kerala, a monsoon‐affected state in southern India. Optimal transplanting dates were derived based on two approaches: (i) probabilities of rainfall events using ClimProb, a PC‐based software package, and (ii) target yields simulated by the CERES‐Rice v3.0 crop growth simulation model. Under rainfed conditions, the optimum transplanting dates were from the 23rd to 26th week for multiple cropping in a year, and from the 26th to 32nd week for a rainfed monocrop. The ClimProb approach used here can be adopted for use elsewhere if climate data are available, and the model approach can also be adopted if specific weather, soils, and crop information is available.
Spatial Scale Requirements for Precision Farming: A Case Study in the Southeastern USA
Authors: Sadler E. John , Busscher Warren J. , Bauer Philip J. , Karlen Douglas L. 
Published: July 2010

AbstractPrecision farming has created a critical need for spatial data on crop yield and related soil characteristics. However, because data are not without cost, users need practical guidelines for spatial resolution on which to collect soil and plant data. Our objectives were (i) to describe variation observed in crop response in the southeastern Coastal Plain of the USA, (ii) to compare it with variation in other regions, and (iii) to offer suggestions for precision farming practices in the southeastern Coastal Plain. From 1985 to 1995, corn (Zea mays L.), wheat (Triticum aestivum L.), soybean [Glycine max (L.) Merr.], and grain sorghum [Sorghum bicolor (L.) Moench] yields were mapped at from 10‐ to 20‐m resolution in an 8‐ha field at Florence, SC. Also available were topography (30‐m resolution), depth to clay (15 m), and in 1993, plant height on one date (9 m), canopy temperature on four dates (1.5 m), and detailed crop and soil information at selected sites. Yield of all crops in all years was significantly (P < 0.0007), though not strongly (median r2 = 0.3), correlated with soil map unit. In 1993, infrared thermometer canopy temperature minus air temperature (∆Tc) was correlated with soil map unit, even on the second day after a 46‐mm rain. Spherical semivariograms fitted to yields had ranges from 57 to 252 m (median = 79 m) and nugget/sill ratios from 0.00 to 0.56 (median = 0.32). Semivariograms for canopy temperature and plant height had ranges from 43 to 77 m. If the spatial structure for common soil characteristics matches the spatial structure for crop response, Coastal Plain soils may require study at finer resolution than the >100‐m grid that is commonly used in precision farming.
Annual Medics and Berseem Clover as Emergency Forages
Authors: Shrestha Anil , Hesterman Oran B. , Squire John M. , Fisk John W. , Sheaffer Craig C. 
Published: July 2010

AbstractSevere winter‐kill of alfalfa (Medicago sativa L.) in some years prompts the need for emergency forages in northern locations. Three annual medic species—barrel medic (M. truncatula Gaertn. cv. Mogul), burr medic (M. polymorpha L. cv. Santiago), and snail medic [M. scutellata (L.) Mill. cv. Sava]—and berseem clover (Trifolium alexandrinum L. cv. Bigbee) and ‘Nitro’ alfalfa were seeded in early spring at East Lansing and the Kellogg Biological Station (KBS) in Michigan in 1994 and 1995. Forage mass was measured at first harvest 60 d after planting and at second harvest 30 d later. Forage mass of annual medics at first harvest ranged from 0.8 to 3.6 Mg ha−1 across locations and years. Berseem clover produced an average forage mass of 2.2 Mg ha−1 at first harvest, which was similar to alfalfa. Crude protein (CP) concentration of annual medics, berseem, and alfalfa ranged from 111 to 210,178 to 233, and 170 to 218 g kg−1, respectively, at first harvest. Regrowth of annual medics (except Mogul) was less than alfalfa or berseem clover; however, the regrowth of Mogul was decumbent and not suitable as hay. Average forage mass and CP concentration of berseem at second harvest was 1.8 Mg ha−1 and 191 g kg−1, respectively, which was similar to alfalfa. Our results indicate that both annual medics and berseem clover can be used as emergency forages in northern locations; however, annual medics have the potential for only one harvest, whereas berseem can be harvested twice during the growing season.
Evapotranspiration and Yield of Corn Grown on Three High Plains Soils
Authors: Tolk Judy A. , Howell Terry A. , Evett Steven R. 
Published: July 2010

AbstractSoil properties that vary within a production area present management challenges to producers when water supplies are limited. We conducted three experiments to determine the influence of soil type and different water management levels on corn (Zea mays L.) yield, evapotranspiration (ET), and water use efficiency. Short‐season corn was grown at low population density in Iysimeters containing monolithic soil cores of Pullman (fine, mixed, superactive, thermic Torrertic Paleustoll), Ulysses (fine‐silty, mixed, superactive, mesic Aridic Haplustoll), and Amarillo (fine‐loamy, mixed, thermic Aridic Paleustalf) soils, at a rain shelter facility in Bushland, TX. Dryland conditions were simulated in 1994 and 1995, with the soils receiving irrigations totaling either 50 or 150 mm in 1994 and either 120 or 200 mm in 1995. In 1996, water management levels were expanded, with the soils receiving weekly irrigation equivalent to 20, 50, 80, and 110% of measured ET. Grain yields for the 3 yr ranged from 389 to 804 g m−2 for the Pullman soil, 559 to 899 g m−2 for the Ulysses soil, and 438 to 736 g m−2 for the Amarillo soil. Low grain yields from corn in the Pullman soil were due to limited water extraction from the lower soil profile. Even under full irrigation (110%), grain yield and leaf area were lower for corn in the Amarillo soil than with the two other soils, possibly due to limited water availability. Soil type effects on corn water use and yield may require different water management strategies for optimum water use efficiency.
Manure, Tillage, and Crop Rotation: Effects on Residual Weed Interference in Spring Barley Cropping Systems
Authors: Stevenson F. Craig , Légère Anne , Simard Régis R. , Angers Denis A. , Pageau Denis , Lafond Jean 
Published: July 2010

AbstractEffects of management practices on crop growth and yields may or may not be mediated through crop‐weed interactions. Our objective was to detect and confirm a relationship between the influence of crop management factors on spring barley (Hordeum vulgare L.) and the potential occurrence of crop‐weed interference. A field study was established on a Normandin clay (fine, mixed, frigid Humic Cryaquept) at Normandin in Québec to investigate the effects of crop rotation, tillage (chisel plow, CP; moldboard plow, MP), and nutrient source on midseason aboveground dry weight and seed yield of barley and residual weed populations. Barley‐weed interference was detected using ANOVA, principal components analysis, and analysis of covariance. A reduction in midseason dry weight (36%) and seed yield (59%) of barley in the CP relative to the MP treatment in 1994 was associated with interference from broadleaf plantain (Plantago major L.) and dandelion (Taraxacum officinale Weber in Wiggers). A 20% reduction in midseason dry weight and seed yield with CP tillage in 1995 was associated with interference from volunteer timothy (Phleum pratense L.) and Kentucky bluegrass (Poa pratensis L.). Barley dry weight and seed yield were 29 and 26% greater in the barley‐forage rotation compared with the monoculture in all years except 1995, despite greater weed pressure in the barley‐forage rotation, confirming the benefits of forages to subsequent crops in a rotation. Compared with mineral fertilizer, application of manure resulted in lower dry weight and seed yield for barley; however, this reduction was not associated with weed interference. In contrast to tillage, crop rotation and nutrient source effects on crop variables appeared mediated through factors other than weed interference.
Dry Matter and Nitrogen Accumulation in Rice Inoculated with a Nitrogenase‐Derepressed Mutant of Anabaena variabilis
Authors: Kamuru Freeman , Albrecht Stephan L. , Allen Leon H. , Shanmugam K. T. 
Published: July 2010

AbstractCyanobacteria contribute to the N economy of flooded rice (Oryza sativa L.) fields by reducing N2 to NH3. The purpose was to determine the extent to which a nitrogenase‐derepressed mutant strain of the cyanobacterium Anabaena variabilis (strain SA‐1), capable of excreting newly fixed N as NH3, could provide N for rice plants grown outdoors in pots. Growth of plants inoculated with the mutant strain was compared with growth of plants inoculated with the parent strain (A. variabilis, strain SA‐0) or fertilized with inorganic N fertilizer [(NH4)2SO4] at rates of 0 (control), 25, 50, and 100 kg N ha−1. Rice plants inoculated with the mutant cyanobacterium produced more panicles than plants inoculated with the parent strain. Dry matter and total N contents of the root, shoot, and grain were significantly greater (P < 0.05) in the plants inoculated with the NH3‐excreting mutant strain than plants that were inoculated with the parent strain of the cyanobacterium. Under these conditions, the contribution of the mutant cyanobacterium to growth and yield of rice plants was equivalent to the application of 71 to 73 kg N ha−1 as (NH4)2SO4. Estimates of the rate of N2‐fixation (acetylene reduction) in pots inoculated with the NH3‐excreting mutant cyanobacterium were about twice the amount observed in pots inoculated with the wild‐type strain, even in the presence of (NH4)2SO4. Pots inoculated with the mutant strain also had more NH3 in the flood water than pots that were inoculated with the parent strain. The NH3‐excreting strain of A. variabilis shows potential for development for use as a biofertilizer in paddy rice production in areas where inorganic fertilizer N is unavailable or expensive and in rice production systems that aim to minimize environmental pollution from inorganic N fertilizers.
Sesbania Tree Fallows on Phosphorus‐Deficient Sites: Maize Yield and Financial Benefit
Authors: Jama Bashir , Buresh Roland J. , Place Frank M. 
Published: July 2010

AbstractRotation of Sesbania sesban (L.) Merr., a fast‐growing N2‐fixing tree, with maize (Zea mays L.) has potential for increasing fertility of tropical soils, where fertilizer use by resource‐poor farmers is limited. At two sites in Kenya (Ochinga, with a Kandiudalfic Eutrudox soil, and Muange, with a Kandic Paleustalf), we compared maize yields and financial returns for (i) sesbania grown for three or four seasons followed by three maize crops (sesbania fallow), (ii) one maize crop followed by natural regrowth of vegetation for three seasons and then three maize crops (natural fallow), and (iii) maize monoculture for seven seasons. After the fallows, plots were split with and without added P. Maize responded to P at both sites. Cumulative grain yields for seven seasons of maize monoculture were 8.4 Mg ha−1 at Ochinga and 5.6 Mg ha−1 at Muange. They were comparable to cumulative maize yields for sesbania fallow (Ochinga, 10.6 Mg ha−1 Muange, 4.5 Mg ha−1) and natural fallow (Ochinga, 7.7 Mg ha−1; Muange, 4.2 Mg ha−1), even though maize was grown for only three or four seasons in the fallow treatments. Sesbania fallow was financially attractive at Ochinga (≥500 mm rain in each season) but not at Muange, where low rainfall (<300 mm in each postfallow season) limited maize yield. Phosphorus fertilization of maize at Ochinga increased (P < 0.2) net benefit for sesbania fallow. Improved fallows have potential to supply nutrients to crops, but they are unlikely to eliminate the need for P fertilizers on P‐deficient soils.
Does Variable Rate Seeding of Corn Pay?
Authors: Bullock Donald G. , Bullock David S. , Nafziger Emerson D. , Doerge Thomas A. , Paszkiewicz Steven R. , Carter Paul R. , Peterson Todd A. 
Published: July 2010

AbstractNot all fields, nor even portions of fields, have the same economically optimal corn plant density. However, until the recent introduction of precision farming, producers could not benefit from these accepted intrafield differences. This field study was conducted on 170 cooperating farmer fields throughout the Midwestern U.S. Corn Belt between 1987 and 1996 and consisted of over 42 000 individual experimental units. At each location, corn (Zea mays L.) was overplanted and thinned to 44 000 to 104 000 plants ha−1. The objective of our field research was to estimate the economic value, to the farmer, of variable rate seeding (VRS) as compared with uniform rate seeding (URS). We first estimated the correlation between field quality and economically optimal plant density. The economically optimal uniform plant density for the Midwest Corn Belt was 67 900 plants ha−1. For every tonne per hectare increase in site quality, as measured by yield potential, the predicted value of the site‐specific economically optimal plant density increased by approximately 1200 plants ha−1. We compared differences in revenues minus seed costs on four simulated fields. The value of VRS, ignoring the costs of VRS equipment and services, ranged from $12.83 ha−1 for farmers with VRS technology and full information to $0.15 ha−1 for farmers with VRS technology but only partial information. Profitable implementation of VRS will require detailed and expensive information regarding site characteristics, production inputs, and stochastic factors. Therefore, VRS will remain economically infeasible for most commercial corn growers until the cost of obtaining such information decreases considerably.
Path Analyses of the Yield Formation Process for Late‐Planted Soybean
Authors: Board James E. , Kang Manjit S. , Harville Bobby G. 
Published: July 2010

AbstractStrategies to increase yield of late‐planted soybean [Glycine max (L.) Merr.] in the southeastern USA would be improved by an understanding of how yield components interact with one another in affecting yield at both the phenotypic and genotypic levels. Our objective was to apply path analyses to data collected from previous studies to determine the relative importance of yield components in the overall yield formation process when environmental and genotypic factors were varied. Path analyses were applied within primary yield components (the predictor variables seed number and seed size, affecting the response variable yield), secondary yield components (the predictor variables pod number and seed per pod, affecting the response variable seed number), and tertiary yield components (the predictor variables pods per reproductive node, reproductive node number, percent nodes becoming reproductive, and node number, affecting the response variable pod number). Path analyses were applied to three data sets constructed from field studies conducted from 1987 to 1993 near Baton Rouge, LA (30° N lat). Phenotypic analyses, which involved altered source strength (canopy assimilatory capacity as indicated by crop growth rate or light interception) during the reproductive period (R1 to R7), affected yield through adjustments in pods per reproductive node and reproductive node number. Pods per reproductive node was also the most important yield component influencing pod and seed number on the genotypic level, although negative compensation between seed number and seed size (at the genotypic level only) precluded a positive effect on yield.