Agronomy Journal

De Battista, J. P.; Bouton, J. H.; Bacon, C. W.; Siegel, M. R.

doi: 10.2134/agronj1990.00021962008200040001xpmid: N/A

Grass endophytes alter the morphology and growth of their hosts. The endophyte (Acremonium coenophialum Morgan‐Jones and Gams) benefits the tall fescue (Festuca arundinacea Schreb.) plant by increasing dry matter production and drought tolerance. Rhizomatous tall fescue was also found to be more persistent and competitive in mixed swards, but the effect of endophyte infection on rhizome expression is unknown. This study was conducted to determine the effect of endophyte removal on rhizome and herbage production of clones and populations of tall fescue. Six clones and four populations (‘Kentucky 31,’ Georgia‐5, Georgia‐Jesup, and Georgia‐Jesup Improved), infected with A. coenophialum and the same clones and populations with the endophyte removed were evaluated for rhizome production, tillering, and herbage and root yield after 12 wk of growth in the greenhouse. No differences in rhizome production were detected between either infected and noninfected clones or populations. However, endophyte infection increased tillering, herbage growth and root growth by 12, 18, and 25%, respectively. A significant (P < 0.01) interaction was detected between endophyte infection and populations for herbage growth with infection increasing herbage growth in Kentucky 31 but decreasing growth in Georgia‐Jesup. Interaction between populations and endophyte infection suggest that the data obtained should not be extrapolated to other germplasm or environmental conditions.

Fowler, D. B.; Brydon, J.; Darroch, B. A.; Entz, M. H.; Johnston, A. M.

doi: 10.2134/agronj1990.00021962008200040002xpmid: N/A

Protein is a primary quality component of cereal grains. Protein concentration is influenced by both environmental and genotypic factors that are difficult to separate. In the present study, a series of cultivar and agronomic trials were conducted on several Saskatchewan soil types with the objective of characterizing the influence of genotype and environment on wheat (Triticum aestivum L.) and rye (Secale cereale L.) grain protein concentration and N use efficiency (NUE) for grain protein production. Minimum protein concentration of 95.4 g protein kg−1 dry grain was expressed when cultivars were produced under high productivity conditions on soils with low total plant available N. Minimum protein concentration was maintained until N was no longer the factor most limiting grain yield. At this point, the protein concentration‐N response curve of a cultivar entered an increased phase. Any environmental (e.g., water or time of N availability) or genotypic factor that increased yield potential also increased the amount of N required to initiate the increase phase of the grain protein concentration N‐response curve. Asymptotic maximum protein concentration was determined by both environmental and genotypic factor. Maximum protein concentration at high levels of N varied from 130 to 231 and 107 to 177 g protein kg−1 dry grain for winter wheat and rye, respectively. At low levels of total available N, the NUE for grain protein production approached 80%. The NUE for grain protein production dropped off rapidly for subsequent increments of N fertilizer, approaching zero for maximum grain yield and reaching zero when maximum grain protein yield was achieved. The end of the increase phase of the protein concentration‐N response curve occurred at approximately the same available N level as maximum grain yield. These observations indicate that management systems designed for the production of cereals with high grain protein concentrations will have a very low NUE for grain and grain protein production.

Morris, R. A.; Villegas, A. N.; Polthanee, A.; Centeno, H. S.

doi: 10.2134/agronj1990.00021962008200040003xpmid: N/A

Water remaining in the soil after flooded rice (Oryza sativa L.) is a major source for crops grown during the dry season. To develop improved management systems, quantitative information describing water extraction from previously puddled and flooded fields is needed. Water used by monocropped and intercropped cowpea [Vigna unguiculata (L.) Walp.] and sorghum [Sorghum bicolor (L.) Moench] treatments grown on a fine, mixed, nonacid isohyperthermic Andaqueptic Haplaquoll after harvesting flooded rice was compared to water lost from a fallow treatment. Determinations were to 1.1 m. Water used before cowpea harvest was similar within a treatment among years, but among treatments monocropped cowpea used 172 mm, monocropped sorghum 135 mm, the intercrop 162 mm, and fallow 121 mm. Water used between cowpea and sorghum harvests ranged from 22 to 118 mm, varying with rainfall after cowpea harvest. Species were compared by expressing grain yields in Mg glucose hectare−1 required to synthesize grain. Glucose equivalent yields from monocropped cowpea ranged from 1.90 to 1.98 Mg glucose ha−1, monocropped sorghum from 1.99 to 3.66 Mg glucose ha−1, and the intercrop from 1.99 to 4.36 Mg glucose ha−1. Mean water use efficiency by monocropped cowpea, monocropped sorghum, and the intercrop was 11.3, 12.4, and 16.5 kg glucose ha−1 mm−1. Monocropped cowpea and the cowpea‐sorghum intercrop each use about 50% more water than is lost from fallow. Whereas the cowpea monocrop and the intercrop use about the same quantities of water when grown during the dry season after rice, the intercrop will use water more efficiently but yields from it will not be as stable as those from monocropped cowpea.

Shaffer, J. A.; Jung, G. A.; Shenk, J. S.; Abrams, S. M.

doi: 10.2134/agronj1990.00021962008200040004xpmid: N/A

Determining the botanical composition of forage samples by near infrared reflectance spectroscopy (NIRS) can save time and expense. The purpose of this study was to test the efficacy of NIRS technology for predicting botanical composition of forage samples. Estimating the number of samples required for reliable calibration equations, determining if pooling calibration samples across locations and years (broad‐based) would improve accuracy and precision, and comparing NIRS errors with experimental and sampling errors were primary objectives. Samples were collected from four different alfalfa (Medicago sativa L.) and ryegrass (Lolium perenne L.) management trials. Calibration samples were hand‐separated into alfalfa, ryegrass, and weed components and each component was dried and weighed. Alfalfa and ryegrass components were then remixed, ground, and processed through a scanning monochromator. Calibration equations for percent alfalfa were chosen using statistical analysis, Random subsets of samples were selected for validation of calibration equations using R2, bias, and standard error of performance (SEP). Broad‐based calibration equations required as little as 200 samples (approximately 5%) to accurately predict botanical composition of alfalfa/ryegrass mixtures with R2 of 0.95, SEP of 6.5%, and bias of −0.3%. Calibration equations generated from each of the four studies separately only marginally improved SEP and slightly increased bias. When botanical composition was estimated on samples from locations not included in the calibration data set, large increases in SEP and bias were observed. Errors associated with NIRS estimations were often one‐half as large as the experimental and sampling errors.

Vasilas, B. L.; Nelson, R. L.; Vanden Heuvel, R. M.

doi: 10.2134/agronj1990.00021962008200040005xpmid: N/A

The labor involved in collecting total plant dry matter limits the number of soybean [Glycine max (L.) Merr.] genotypes that can be evaluated for N2 fixation. Therefore, a 2‐yr experiment was conducted on a Flanagan silt loam (fine, montmorillonitic, mesic Aquic Argiudoll) to determine if genotypic differences in plant N derived from fixation (N2 fixed) and percentage of plant N derived from fixation (% Ndfa) could be detected by isotope dilution or difference (total N) method analysis of whole plant samples (whole plant sample including abscised material), shoot samples (whole plant samples‐abscised material), or seed samples. Five experimental soybean lines derived from a ‘Williams’ ✕ ‘Kanrich’ cross and ‘Harosoy’ were tested. Estimates of N2 fixed and % Ndfa generated by isotope dilution analysis of whole plant samples ranged from 36 to 113 kg ha−1 and 17 to 48%, respectively. More genotypic separations were possible with isotope dilution than with the difference method. Separation on the basis of % Ndfa by isotope dilution was not affected by plant sample. More genotypic separations on the basis of N2 fixed were possible by isotope dilution analysis of whole plant or shoot samples than by analysis of seed samples.

McCauley, G. N.

doi: 10.2134/agronj1990.00021962008200040006xpmid: N/A

Sprinkler irrigation of rice (Oryza sativa L.) could conserve water and lower production costs. Tests were conducted for 3 yr (1982–1984) on a Beaumont clay soil (Entic Pelludert) to evaluate 12 rice cultivars under flood and three levels of sprinkler irrigation. Plant growth (height), plant development (days to heading and harvest), yield, yield components, and quality were monitored. Irrigation treatments were main plots and cultivars were subplots. Irrigation treatments 100, 50, and 25 replaced 100, 50, and 25% of estimated evapotranspiration (ETe). Total water applied was 931 mm (1982), 1171 mm (1983), and 1061 mm (1984) for Treatment 100. These applications exceeded the ETe of flooded rice by 331 to 571 mm. Compared to flood irrigation, sprinkler treatments reduced plant height by 0.09 to 0.28 m. Days to heading varied by cultivar and irrigation treatment while days to harvest was not affected by the irrigation treatments. Milled grain was not influenced by irrigation. Compared to the average yield for flood irrigation, sprinkler irrigation reduced yield over 20% with Treatment 100 and key cultivar yields were reduced 28%. Yield loss from Treatment 100 could not be attributed to weeds, diseases, or water availability. Yield loss was due to reduced florets/panicle and reduced fertile florets. With a yield differential in excess of 20%, sprinkler irrigation does not appear to be a viable alternative to conventional flood irrigation in traditional rice‐growing areas.

Crabtree, R. J.; Prater, J. D.; Mbolda, P.

doi: 10.2134/agronj1990.00021962008200040007xpmid: N/A

Inadequate amounts and distribution of rainfall are most often the major limiting factors to crop production in the southern Great Plains. This is especially true for summer crops, whether grown in mono‐ or double‐cropping situations. This study was conducted at the Oklahoma Vegetable Research Station, Bixby, OK from 1976 to 1987 on a Wynona silt loam soil (Cumulic Haplaquolls) with 0 to 1% slope. The objective was to determine the effects of long‐term double‐cropping on the potential for sustaining grain yields of wheat [Triticum aestivum (L.) em. Thell], soybean [Glycine max (L.) Merr.], and grain sorghum (Sorghum bicolor L. Moench) produced on the same land under rainfed conditions. Over a 12‐yr period monocropped wheat averaged 3050 compared with 2510 and 2450 kg ha−1 when double‐cropped with soybean and grain sorghum, respectively. Conventionally tilled monocropped soybean and grain sorghum and no‐till double‐cropping of both soybean and grain sorghum after wheat produced grain 11 out of 12 yr. Monocropped soybean averaged 2470 compared with 1930 kg ha−1 for no‐till double‐cropped soybean. Monocropped grain sorghum averaged 5130 compared with 4200 kg ha−1 for double‐cropped grain sorghum. During the years of near 30‐yr average rainfall amounts and distribution (5 out of 11), yields of double‐cropped soybean and grain sorghum were competitive with those of monocropped soybean and grain sorghum. These results indicate that yields of double‐cropped wheat, soybean, and grain sorghum can be sustained over long periods of time. In eastern Oklahoma double‐cropping on a deep medium textured soil produced more total grain that resulted in more efficient use of climatic, land, labor, and equipment resources when compared with monocropping.

McBee, G. G.; Miller, F. R.

doi: 10.2134/agronj1990.00021962008200040008xpmid: N/A

Declining fossil fuel supplies has stimulated development of alternate energy sources from plant biomass. Sorghum [Sorghum bicolor (L.) Moench] has been recognized as an excellent crop for anaerobic fermentation to methane because of high carbohydrate content of the vegetative biomass. This study was conducted to determine quantities of hemicellulose (HC), cellulose (CL), lignin (LG), and nonstructural carbohydrates (NSC) partitioned between stems and blades of a spectrum of sorghums. Six entries, E35‐1, AT✕ 623 ✕ ‘Rio’ (primarily forage types), Giza‐114 (biomass type), RT✕432, AT✕623 ✕ RT✕432, and AT✕623 ✕ RT✕430 (grain types), were produced on a Ships clay (very‐fine, mixed, thermic Udic Chromustert). Plants were harvested at physiological maturity of the kernels, separated into stem and leaf blade fractions, and analyzed for HC, CL, LG, and NSC. Structural component content ranged from 716 to 516 g kg−1 for stems and 652 to 567 g kg−1 for the blades. Stems contained 12 to 39 g kg−1 more LG than blades across entries. Content of HC in blades exceeded that of stems, whereas CL levels were higher in stems than blades for all entries except E35‐1. The ratio of HC/CL ranged from 0.7 to 0.9 in the stems and 1.1 to 1.3 in the blades. Rind and pith of Giza‐114, AT✕623 ✕ Rio and AT✕623 ✕ RT✕430 contained more structural components in the rind. The quantity of NSC was 74 to 216 g kg−1 higher in the stems than blades for all entries. Sorghum stems may contain large quantities of NSC and structural components, but blades are low in NSC for purposes of digestion or methanogenesis.

Benoit, G. R.; Olness, A.; Van Sickle, K. A.

doi: 10.2134/agronj1990.00021962008200040009xpmid: N/A

The effect of constant day/night, average daily, or instantaneous temperatures on plant growth has been extensively documented. Little work has looked at how plant growth under field conditions may be influenced by variations in the day/night temperature combinations experienced. Our objective was to evaluate the effect of day/ night temperature differences on daily corn (Zea mays L.) growth. To accomplish this, corn was grown with and without irrigation (four replications of three planting dates in 1983, 1984, and 1985) on a Hamerly clay (Aerie calciaquoll, fine‐loamy, frigid) at Morris, MN. Hourly soil and air temperature, weekly profile soil water content, and daily precipitation were recorded. Leaf area and plant height were measured daily from eighth leaf to 100% silking. Only plant size data from consecutive days of complete measurements were used with daily maximum and minimum temperatures to establish temperature‐growth rate relations. Leaf area and plant height prediction equations developed from stepwise multiple regression techniques were used to construct percent growth (leaf area and plant height) vs. maximum and minimum temperature response surfaces. Equations were developed for all possible combinations of planting date and irrigation level for each year and all years combined. Combined data showed general relations representative of those shown by individual data sets between percent growth and temperature. Plant height and leaf area predictive equations for combined data have highly significant r2 values of 0.72 and 0.54, respectively. The data shows that percent increase in plant size decreases over time as size at the start of any 24‐h‐growth period increases and that each daily maximum temperature has a successive apparent optimum night temperature for growth.

Mooso, G. D.; Wedin, W. F.

doi: 10.2134/agronj1990.00021962008200040010xpmid: N/A

Relationships between alfalfa (Medicago sativa L.) and associated grasses in a plant community are complex. A concern has developed whether alfalfa was, in fact, benefiting from grass association. A field study was conducted to describe the changes in canopy components of alfalfa‐reed canarygrass (Phalaris arundinacea L.) and alfalfa‐orchardgrass (Dactylis glomerata L.) mixtures. Alfalfa‐grass mixtures of one row of grass between two rows of alfalfa and one row of alfalfa between two rows of grass were planted in a repeating pattern. Monocultures of each species and four binary mixtures were sampled for total, alfalfa and grass component, and stratified alfalfa yields were measured at 10, 20, 30, 40, and 50 d of spring and summer regrowth for 2 yr. Planting pattern, grass species and season of growth affected botanical composition and yield of alfalfa‐grass mixtures. Alfalfa‐grass mixtures yielded more than alfalfa monocultures during only one spring growth cycle. During summer regrowth, alfalfa‐grass mixtures were less productive than alfalfa monocultures. In spring, reed canarygrass accounted for a greater proportion of the total yield than orchardgrass, whereas the two grasses were similar during summer. Grass yields of mixtures were not affected by alfalfa association. The results of this study suggest that alfalfa‐grass mixtures offer little yield advantage over alfalfa monocultures when harvested as hay.