bluuebunny/crossref_metadata_2025_split huggingface dataset:
Leaf Emergence on Potato Stems in Relation to Thermal Time
Authors: Cao Weixing , Tibbitts Theodore W. 
Published: July 2010

AbstractFor simulation of foliar development of potato plants (Solanum tuberosum L.), it is necessary to quantify the responses of leaf emergence to major environmental factors. This study was conducted to determine the relationship of leaf emergence on potato stems to growing degreedays (GDD) under varied temperature patterns over different growth periods. In each of two duplicate experiments in controlled environments, potato plants were grown for 63 d after transplanting of tissue culture plantlets into 20‐L pots containing peat‐vermiculite mix. Four treatments were maintained, involving two constant temperatures of 17 and 22°C and two changed temperatures of 17‐22‐17 and 22‐17‐22°C over three 21‐d periods under constant vapor pressure deficit of 0.60 kPa and photosynthetic photon flux density of 430 µmol m−2 s−1 for a 14‐h photoperiod. The first period was the first 21 d of plant growth after transplanting, the second 21‐d period coincided with plant enlargement and tuber initiation, and the third period coincided with tuber enlargement. Leaf numbers on main stems and uppermost apical branches were recorded every 2 to 3 d during the course of the experiments. This leaf number increased linearly with accumulated GDD over the whole experiment duration for each of the four treatments, whether the temperature was constant or changed. The phyllochron in GDD per leaf (6°C base temperature) was lowest at constant 17°C (19.2 GDD), highest at constant 22°C (22.8 GDD), and intermediate at the changed temperatures ( ≈21.3 GDD). Detailed analysis of the leaf emergence rates during each of the three 21‐d periods indicates that the phyllochron at either 17 or 22°C was also slightly lower during the second 21‐d period than during the first and third 21‐d periods. The total leaf number increased with increasing total GDD among the treatments, primarily from varied leaf number on apical branches. The data suggest that a constant phyllochron for a given growth location and calendar time may provide sufficient accuracy for predicting leaf emergence on potato stems in the field environment.
Water and Nitrogen Effects on Winter Wheat in the Southeastern Coastal Plain: I. Grain Yield and Kernel Traits
Authors: Frederick James R. , Camberato James J. 
Published: July 2010

AbstractUnderstanding how environmental factors affect winter wheat (Triticum aestivum L. emend. Theil.) responses to spring N application is an important component of economically and environmentally sound winter wheat production on the southeastern Coastal Plain of the USA. Increasing the amount of N applied to winter wheat grown in this region has been shown to result in a greater severity of drought stress during grain fill and lower individual kernel weights. This 2‐yr field study was conducted to determine whether drought‐induced reductions in kernel weight with high spring N rates are the result of decreases in the rate or the duration of kernel growth. Winter wheat was grown with different rates of spring‐applied N (0, 45, 90, and 135 kg N ha−1) under both irrigated and nonirrigated conditions. Increases in the rate of springapplied N resulted in a greater severity of soil water deficits under nonirrigated conditions. Quadratic increases in grain yield and kernel number per square meter occurred in response to increased spring N under both levels of soil water treatment. Grain yield and individual kernel weight responses to irrigation were greater at the higher N rates than at the lower N rates. Over both years, the average increase in individual kernel weight due to irrigation was 3.9 and 13.3% at the 0 and 135 kg N ha−1 rates, respectively. Similar responses were found for the effective filling period (EFP), where irrigation increased the EFP an average of 3.2 and 14.5% at the lowest and highest spring N rates, respectively. Soil water treatment had no effect on kernel growth rate. Results indicate that high rates of spring‐applied N increase the severity of drought stress in nonirrigated winter wheat grown on the Coastal Plain, resulting in reductions in the EFP and, consequently, kernel weight.
Comparison of Normal and Opaque‐2 Maize Genotypes Used for Corn Cob Mix in Pig Feeding
Authors: Pintér Lajos , Burucs Zoltán , Alföldi Zoltán 
Published: July 2010

AbstractOpaque‐2 (o2) maize (Zea mays L.) contributed significantly to the quality improvement of maize breeding in the 1960s, but did not become popular because of a lower yield, a result of its shorter grain‐filling period. This characteristic, however, could prove to be advantageous for use in corn cob mix (CCM), which is popular in the cold‐wet regions of Europe. A research program including a 3‐yr field trial, an in vivo pig (Sus scrofa) study with fermented CCM, and a farm‐scale fattening test was conducted to evaluate the prospect of o2 for CCM production and utilization. Opaque‐2 yielded as much CCM at the CCM ripening stage (600 g kg−1 grain DM) as did the normal version. Due to its shorter grain‐filling period, 02 can accumulate more assimilates at a higher grain moisture content than the normal maize. Results from in vivo pig trials showed that o2 was superior in N retention and in the biological value of protein compared with the normal genotype. Consequently, using o2 can balance the feed value and reduce the soybean [Glycine max (L.) Merr.] content in the ration for fattening pigs by 27%. The quality of the meat of slaughtered pigs fed with o2 and less soybean was comparable to that of pigs fed with normal maize and larger supplement of soybean protein. Improved o2 genotypes may be an alternative source of CCM production in countries where the climate is not very favorable for soybean production and where alternative protein supplements are not readily available.
Crop and Nitrogen Yield in Legume‐Based Rotations Practiced with Zero Tillage and Low‐Input Methods
Authors: Izaurralde R. C. , Juma N. G. , McGill W. B. , Haderlein L. , Choudhary M. 
Published: July 2010

AbstractThough legumes are beneficial in crop rotations, there is limited information on how tillage system‐crop sequence interactions influence crop yield and N production. To see if biomass and N yields in short‐term legume‐based rotations under zero tillage (ZT) and low‐input (LI) production methods can equal those in cereal monocultures under ZT and conventional tillage (CT), field experiments were conducted in Alberta, Canada, from 1989 to 1992 at Ellerslie (Typic Cryoboroll soil) and Breton (Typic Cryoboralf). Treatments at each site consisted of (i) two 4‐yr rotations, each with the same crop sequence but different tillage methods, and (ii) four continuous barley treatments in 2 ✕ 2 factorial combination of tillage and fertilizer N. The crop sequence was barley (Hordeum vulgare L.)‐barley and field pea (Pisum sativum L.) intercrop‐barley‐fababean (Vicia faba L.). At Ellerslie, tillage for weed control and seedbed preparation was either CT‐LI or ZT. At Breton, one rotation used the LI approach; the second used deep tillage (DT). Weeds on CT and ZT were controlled with either pre‐ or postemergence herbicides. No herbicides were applied to LI treatments at either site or to the DT treatment at Breton. Yields of barley following legumes under ZT were similar to those of fertilized continuous barley. With nonchemical weed‐control methods, weed competition reduced yields of barley following legumes by 24% compared with fertilized continuous barley. The increased fababean yield measured under DT was associated with improved rooting conditions and water extraction. The equivalent N‐fertilizer value of legume residues with similar weed‐control levels averaged 19 kg ha−1. Except for the LI system, legume‐based rotations produced, over the 4‐yr cycle, amounts of N equivalent to continuous cereal systems. Resource use efficiency of legume‐based rotations, as measured by net‐N yields, was equivalent to continuous systems at Breton, but somewhat reduced at Ellerslie.
Wheat Response to Row Spacing in Relay Intercropping Systems
Authors: Porter Paul M. , Khalilian Ahmad 
Published: July 2010

AbstractRelay intercropping of soybean [Glycine max (L.) Merr.] or cotton [Gossypium hirsutum L.] into standing wheat [Triticum aestivum L.] allows for earlier planting of the summer crop than with sequential double‐crop systems. Relay intercropping has been evaluated using modifications of standard planting and harvesting equipment as well as specifically designed equipment. In most relay intercropping systems, wheat is drilled in the fall in a row pattern that provides traffic‐tire lanes as guides for planting the summer crop. Also, row spacing for wheat in relay intercropping is usually wider than for conventionally planted wheat. This field study, conducted during 1991‐1992 and 1992‐1993 near Blackville, SC, on a Varina loamy sand (clayey, kaolinitic, thermic Plinthic Paleudults), compared the yield and yield component response of soft red winter wheat produced with two different intercropping production schemes to the yield and yield component response of conventionally planted wheat. Yields of wheat planted in skip‐row schemes designed to allow for relay intercropping of either soybean or cotton were not significantly different from yield of conventionally planted wheat under the given experimental conditions. For conventionally planted wheat, wheel traffic on certain rows reduced yields by as much as 50% compared with nontraffic rows. In the schemes designed to allow for relay intercropping, wheat grown with wider‐spaced rows (0.31‐0.61 m) compensated with respect to yield on an area basis compared with wheat grown with conventionally spaced rows (0.15‐0.20 m).
Dynamics of Moisture, Nitrogen, and Striga Infestation on Pearl Millet Transpiration and Growth
Authors: Boukar Ibrah , Hess Dale E. , Payne William A. 
Published: July 2010

AbstractThe parasitic weed Striga hermonthica (Del.) Benth. (witchweed) is a major biotic constraint to pearl millet [Pennisetum glaucum (L.) R. Br.] production in Sahelian Africa. To address this constraint, more information is needed on host‐parasite relations under varying conditions of soil water and nutrient availability typically found in the Sahel. The dynamics of moisture, N, and Striga infestation on pearl millet transpiration and growth were investigated. The effects of Striga infestation, water deficit stress, and N availability on root length and dry weight, shoot dry weight, and transpiration ratio (TR; g dry matter kg−1 transpiration) were evaluated. Millet was grown in 36‐L pots for 45 d in a glasshouse, using two levels of water and N availability and three levels of Striga infestation. With no N, shoot dry weight of uninfested millet plants was low. Shoot weight was further reduced by 42% at the high level (71 000 seeds pot−) of Striga infestation. With the addition of 60 kg ha− of N, shoot weight of uninfested millet plants increased five‐ to sixfold. A reduction of 36% in shoot weight was observed in plants with N and highest infestation of Striga. Root dry weight was also low without N, but unaffected by Striga infestation. With the addition of N, root dry weight of millet plants increased under adequate and water‐stressed conditions. Root length in the upper 0.10 m followed a similar trend. Transpiration ratio decreased due to Striga infestation, increased with reduced water availability, and increased with greater N supply. The number of Striga haustoria attached to millet roots increased with water deficit stress, N addition, and increased level of infestation. The number of haustoria per unit root length increased with water stress and Striga infestation, but was substantially decreased by N addition. The number of haustoria per unit root length increased linearly with the total number of haustoria present. This slope was independent of water supply, but was four times greater for unfertilized plants compared with those receiving N. This study confirms that Striga attack is more severe in the presence of nutrient and water stress, and reduces whole‐plant water‐use efficiency. It also suggests a physiological mechanism by which N addition permits the host to better resist Striga attack.
Temporal Changes in Soybean Gas Exchange Following Simulated Insect Defoliation
Authors: Peterson Robert K. D. , Higley Leon G. 
Published: July 2010

AbstractCharacterizing the influence of arthropods on plant gas exchange processes, such as photosynthesis, water‐vapor transfer, and respiration, is important because these processes are crucial determinants of plant growth, yield, and fitness. Despite the relatively extensive research that has been conducted on physiological responses of soybean [Glycine max (L.) Merrill] to defoliation injury, transient gas exchange parameters, such as photosynthesis, stomatal conductance, and respiration, have not been measured to determine if they are altered after the injury process. A better understanding of these responses would improve the development of plant response models to arthropod stress, which are needed to determine economic injury levels used in pest management programs. Therefore, this study was conducted to characterize the gas exchange responses of soybean following leaf‐mass consumption. The study was conducted from 1992 through 1994 on soybean (‘Kenwood’ and ‘Clark’) in a field environment. The experimental design was a randomized complete block with six replications in 1992, four replications in 1993, and seven replications in 1994. Rows were the blocking factor. Various defoliation treatments were imposed using a cork‐borer punch. Each treatment replicate was assigned to a leaflet on a separate plant. Gas exchange parameters were measured using a portable photosynthesis system and a steady‐state porometer. At approximately 0.25, 1, 3, and 24 h after injury, gross tissue removal did not affect gas exchange parameters of soybean leaflets. Our results support previous research indicating that gross tissue removal does not appreciably alter photosynthetic rates of injured soybean leaves.
Lower Limit of Soil Water Availability
Authors: Savage Michael J. , Ritchie Joe T. , Bland William L. , Dugas William A. 
Published: July 2010

AbstractEstimating the available soil water reservoir is needed for developing a strategy for optimum management of rainfed crops in marginal dry regions. Previous research on measurement of the lower limit water content of soil water availability (required for calculation of the total soil water reservoir) has shown unexplained discrepancies between field estimates of the water content at which plants are dead or dormant due to soil water deficit and laboratory estimates of the water content at a water potential of − 1.5 kJ kg−1. Whether such discrepancies are due to sample size, handling, or the choice of − 1.5 kJ kg−1 as the lower limit is not clear. This study was designed to determine what the limit is under controlled conditions, and to test the appropriateness of the −1.5 kJ kg−1 value. We used in situ soil psychrometers to measure soil water potential (Ψ) as water was withheld from cotton (Gossypium hirsutum L.) plants in a rain‐sheltered lysimeter monolith and from sorghum [Sorghum bicolor (L.) Moench] in glasshouse pots. The lower limit Ψ was − 2.2 kJ kg−1 in the lysimeter experiment and < − 2.5 kJ kg−1 in the glasshouse. With the lysimeter, the difference between the soil water content corresponding to − 2.2 kJ and − 1.5 kJ kg−1 was <0.01 m3 m−3. Water potential at the greatest measurement depth (2.1 m) decreased rapidly from near 0 to − 1.8 kJ kg−1 over a period of 30 d, while root length density increased from nearly 0 to 2400 m−3. At an advanced stage of soil water deficit, there was limited upward movement of water from depths >2.1 m. No Ψ oscillations, corresponding to so‐called hydraulic lift or nocturnal water transport between soil layers, were found at any depth in the lysimeter (0.5–2.1 m). Our results suggest that for water balance calculations requiring absolute accuracy for the water balance of the soil reservoir, the choice of the − 1.5 kJ kg−1 soil water potential is appropriate and corresponds closely to the field lower limit of soil water availability.
Simulating Maize Emergence Using Soil and Climate Data
Authors: Weaich Karl , Bristow Keith L. , Cass Alfred 
Published: July 2010

AbstractExperimental programs aimed at improving seedling establishment in the semiarid tropics require quantitative information concerning the interaction between the seedbed environment and preemergent seedling growth. The model here described links a soil heat and water model, a soil strength model, and a temperature‐dependent maize (Zea mays L.) shoot growth model to predict the response of preemergent maize seedlings to a physical environment typical of the semiarid tropics. In comparisons with field measurements taken in the semiarid tropics under high drying rate conditions, the model simulations yielded accurate representations of soil water, temperature, strength, and preemergent shoot growth of maize. The model was also used to compare the effects of radiation‐ vs. wind‐dominated evaporative demand on preemergent seedling growth in a hardsetting seedbed. Results showed that under radiation‐dominated conditions, the early onset of high soil temperature limited seedling growth, while under wind‐dominated conditions, the early development of high soil strength affected seedling growth first. Simulations using surface mulch as an ameliorative management practice showed that mulch greatly reduced soil evaporation, thereby eliminating high soil strength as a limitation to seedling establishment. Results indicate that the model is a potentially useful tool for investigating the likely effects of soil and climate on seedling emergence.
Simulation Models: Science, Snake Oil, Education, or Engineering?
Authors: Passioura John B. 
Published: July 2010

AbstractCrop simulation models can be divided into two groups: those that aspire to improve our understanding of the physiology and environmental interactions of crops (science), and those that aspire to provide sound management advice to farmers or sound predictions to policy makers (engineering). These quite different aspirations require quite different models. Scientific models are mechanistic. With a few exceptions, they have failed to meet their aspirations. They are typically flawed by being based on untestable guesses about the processes that control growth. They may, however, provide useful self‐education for their developers. The best engineering models are based on robust empirical relations between plant behavior and the main environmental variables. Because of their empirical nature, we should not expect them to apply outside the range of the environmental variables used in their calibration. Within their calibrated ranges, however, some have proved useful in providing sound management advice. It is hard to see a useful role, other than self‐education, for models that fall between the scientific and the engineering types.
Critical Light Interception during Seed Filling for Insecticide Application and Optimum Soybean Grain Yield
Authors: Board James E. , Wier Alan T. , Boethel David J. 
Published: July 2010

AbstractRelationships between defoliation, light interception, and grain yield for soybean [Glycine max (L.) Merr.] during the last half of the seed filling period are not fully understood. Because defoliating insect pests in the southeastern USA frequently attack soybean during this period, knowledge of such relationships would aid development of criteria for economic insecticide application. Our first objective was to determine the efficacy of using light interception and leaf area index as criteria for economic insecticide application to manage defoliating insect pests. The second objective was to determine the effects of partial and total defoliations during seed filling on grain yield and grain yield formation. ‘Centennial’ soybean (Maturity Group VI) was planted in 1993 and 1994 near St. Gabriel, LA. Experimental design was a randomized complete block in a split‐plot arrangement. Main plots were the temporal midpoint and 3/4‐point seed‐filling stages. Split plots were four defoliation treatments: 0% leaf removal (control), 37 to 41% leaf removal, 56 to 61% leaf removal, and 100% leaf removal. At the temporal midpoint, grain yield declined linearly as light interception fell from 93 to 50%. Thus, for a crop achieving near‐maximal light interception, insecticide application would be recommended whenever light interception at the midpoint seed‐filling stage fell below 93%. Yield and light interception were not closely related at the 3/4‐point seed‐filling stage. Maintenance of maximal grain yield (yield at 0% defoliation) required retention of at least 39% of the leaf area at this time. In conclusion, light interception potentially could be used as an insecticide application criterion at midpoint seed‐filling stage, but not the 3/4‐point. Partial defoliation at the midpoint will affect grain yield if it reduces light interception below 93%, whereas at the 3/4‐point total defoliation is required to affect grain yield.
Evaluation of Two Maize Models for Nine U.S. Locations
Authors: Kiniry Jim R. , Williams Jimmy R. , Vanderlip Richard L. , Atwood Jay D. , Reicosky Donald C. , Mulliken Jerry , Cox William J. , Mascagni Henry J. , Hollinger Steven E. , Wiebold William J. 
Published: July 2010

AbstractCrop models can be evaluated based on accuracy in simulating several years' yields for one location or on accuracy in simulating long‐term mean yields for several locations. Our objective was to see how the ALMANAC (Agricultural Land Management Alternatives with Numerical Assessment Criteria) model and a new version of CERES‐Maize (Crop‐Environment Resource Synthesis) simulate grain yield of rainfed maize (Zea mays L.). We tested the models at one county in each of nine states: Minnesota, New York, Iowa, Illinois, Nebraska, Missouri, Kansas, Louisiana, and Texas (MN, NY, IA, IL, NE, MO, KS, LA, and TX). Simulated grain yields were compared with grain yields reported by the National Agricultural Statistical Service (NASS) for 1983 to 1992. In each county we chose a soil commonly used in maize production, and we used measured weather data. Mean simulated grain yield for each county was always within 5% of the mean measured grain yield for the location. Within locations, measured grain yield was regressed on simulated grain yields and tested to see if the slope was significantly different from 1.0 and if the y‐intercept was significantly different from 0.0, both at the 95% confidence level. Only at MN, NY, and NE for ALMANAC and at MN, NY, and TX for CERES was slope significantly different from 1.0 or intercept significantly different from 0.0. The CVs of simulated grain yields were similar to the those of measured yields at most sites. Also, both models were appropriate for predicting an individual year's yield for most counties. Values for plant parameters, such as heat units for development and the harvest index, and values for soil parameters describing soil water‐holding capacity offer users reasonable inputs for simulating maize grain yield over a wide range of locations.