Days After Seeding Research Articles

Mulch Depth Affects Weed Germination

Abstract With environmental concerns increasing, non-chemical weed control in container plant production is increasing in the United States. Pine bark mini-nuggets were evaluated as a non-chemical weed control technique for two weed species; Chamaesyce maculata (L.) Small (spotted spurge) and Eclipta alba (L.) Hassk.(eclipta). On June 19, 2006, seed (25 per container) were directly placed on the potting substrate surface of #3 containers before mulching with pine bark mini-nuggets to a depth of either 0, 1.27 or 2.54 cm (0, 0.5 or 1.0 in). Additional treatments consisted of applying the mini-nugget mulch at either 1.27 or 2.54 cm (0.5 or 1.0 in) on the potting substrate then overseeding with either spotted spurge or eclipta. Eclipta number per container were 87% less 60 days after seeding (DAS) with the 1.0 in mulch depth compared to non-mulched. Furthermore, spotted spurge fresh weight (FW) was reduced by 45 and 87% (0.5 and 1.0 in, respectively) compared to the non-mulched treatment. The experiment was repeated on August 30 and spurge number per container was 90% less 60 DAS in the 1.0 inch mulch treatment compared to the non-treated containers. A third and fourth experiment also demonstrated that pine bark mini-nuggets have potential to provide non-chemical weed control in nursery crops grown in #3 containers. Results, suggest that with proper application pine bark mini-nuggets can enhance weed control in container nurseries.

Viabilidade econômica de doses e parcelamentos da adubação nitrogenada na cultura do milho em LATOSSOLO VERMELHO Eutrófico

Nitrogen is the nutrient that is most absorbed by the corn crop, with the most complex management, and has the highest share on the cost of corn production. The objective of this work was to evaluate the economic viability of different rates and split-applications of nitrogen fertilization, as such as urea, in the corn crop in a eutrophic Red Latosol (Oxisol). The study was carried out in the Experimental Station of the Regional Pole of the Sao Paulo Northwest Agribusiness Development (APTA), in Votuporanga, State of Sao Paulo, Brazil. The experimental design was randomized complete blocks with nine treatments and four replications, consisting of five N rates: 0, 55, 95, 135 and 175 kg ha -1 , 15 kg ha -1 applied in the seeding and the remainder in top dressing: 40 and 80 kg ha -1 N at forty days after seeding (DAS), or ½ + ½ at 20 and 40 DAS; 120 kg ha -1 N split in ½ + ½ or 1/3 + 1/3 + 1/3 at 20, 40 or 60 DAS; 160 kg ha -1 N split in ¼ + 3/8 + 3/8 or ¼ + ¼ + ¼ + ¼ at 20, 40, 60 and 80 DAS. The application of 135 kg ha -1 of N split in three times provided the best benefit/cost ratio. The non-application of N provided the lowest economic return, proving to be unviable.

Evaluation of the antioxidant capacity of lupin sprouts germinated in the presence of selenium

Antioxidant capacity of 5 DAS (days after seeding) lupin sprouts germinated in the presence of selenate or selenite was determined by cyclic voltammetry (CV), Folin-Ciocalteu reagent (FCR) application and photochemiluminescence (PCL) methods. The hydrophilic (80% methanol) and lipophillic (hexane/methanol) extracts of 5 DAS lupin sprouts germinated in the absence of selenium (control sprouts) showed higher antioxidant capacity than ungerminated seeds. Five DAS sprouts produced in the presence of higher concentration of selenate or selenite (6–8 mg/L) showed increased total antioxidant capacity formed by both hydrophilic and lipohillic antioxidants when evaluated by CV and FCR methods. The hydrophilic extracts from sprouts produced in the presence of low concentration of selenate (2–6 mg/L) showed a significantly higher antioxidant capacity of water-soluble compounds (PCL ACW) while no changes were noted in those germinated in the presence of the highest concentration in relation to the control sprouts. In contrast, the antioxidant capacity of lipid-soluble compounds (PCL ACL) lowered significantly in relation to the control sprouts. The similar changes in antioxidant capacity of sprouts produced in the presence of selenite were found by both PCL assays. Comparison of PCL with CV and FCR reducing capacity assays has shown that these methods yielded considerably different chemical information. Moreover, the changes in total antioxidant and total reducing capacity of sprouts germinated in the presence of either selenate or selenite provided by CV and FCR assays were higher than those obtained by photochemiluminesce measurements. It can be suggested to use 6–8 mg/L of selenite rather than selenate in order to obtain a lupin sprouts with high antioxidant capacity.

Allelopathic effect of the root exudates of K21, a potent allelopathic rice

An inhibitory effect of the phenolic compounds released from the roots of K21, a newly bred potent allelopathic rice, was investigated in comparison to its male parent, Kouketsumochi, and its female parent, Dongjinbyeo. The inhibitory rates of the root exudates of K21 and both of its parents, collected at 5 day intervals, on the shoot growth of Echinochloa crus‐galli var. praticola exhibited an increasing trend from 19–34 days after seeding (DAS). However, the root exudates of K21, at concentrations of 0.5, 1.0, and 2.0%, showed a greater inhibitory effect than those of its female parent on the growth of E. crus‐galli var. praticola at the earlier collection dates. Nine phenolic compounds were identified; the total amount of phenolic compounds in the exudates increased from 19–34 DAS in both K21 and its male parent, but not much in the female parent. The subsequent increase in the amount of total phenolic compounds in the root exudates of the later investigation dates and the trend of increasing inhibitory rates on the shoot growth of E. crus‐galli var. praticola at higher exudate concentrations imply that the increased amount of phenolic acids in the root exudates of K21 secreted on the subsequent dates could be related to its greater allelopathic effects.

Influence of arbuscular mycorrhizae on soil P dynamics, corn P-nutrition and growth in a ridge-tilled commercial field

Ridge-tilled corn (Zea mays L.) could benefit from arbuscular mycorrhizal (AM) fungi. Under low soil disturbance, AM hyphal networks are preserved and can contribute to corn nutrition. A 2-yr study was conducted in the St. Lawrence Lowlands (Quebec, Canada) to test the effects of indigenous AM fungi on corn P nutrition, growth, and soil P in field cropped for 8 yr under ridge-tillage. Phosphorus treatments (0, 17, 35 kg P ha-1) were applied to AM-inhibited (AMI) (fungicide treated) and AM non-inhibited (AMNI) plots. Plant tissue and soil were sampled 22, 48 and 72 days after seeding (DAS). P dynamics was monitored in situ with anionic exchange membranes (PAEM) from seeding to the end of July. AMNI plants showed extensive AM colonization at all P rates. At 22 DAS, AMI plants had decreased growth in the absence of P inputs, while AMNI plants had higher dry mass (DM) and P uptake in unfertilized plots. The PAEM was lower in the AMNI unfertilized soils in 1998 and at all P rates in 1999, indicating an inverse relationship between P uptake and PAEM. At harvest, grain P content of AMNI plants was greater than that of AMI plants. In 1998, only AMI plants had decreased yield in the absence of P fertilization. In 1999, AMNI plants produced greater grain yield than AMI plants at all P rates. AM fungi improve the exploitation of soil P by corn thereby maintaining high yields while reducing crop reliance on P inputs in RT. Key words: Arbuscular mycorrhizae, ridge-tillage, soil P dynamics, corn, P nutrition

Effect of Foliar Trimming and Fungicides on Apothecial Number of Sclerotinia sclerotiorum, Leaf Blight Severity, Yield, and Canopy Microclimate in Carrot

Foliar trimming of the carrot canopy has potential for reducing the severity of Sclerotinia (Sclerotinia sclerotiorum) rot of carrot (Daucus carota subsp. sativus). The effect of trimming the carrot foliage once or twice, with and without fungicide application, was examined on carrot plants grown on organic soil for 3 years at the University of Guelph-Muck Crops Research Station in Ontario, Canada. The number of S. sclerotiorum apothecia, carrot leaf blight (CLB; Alternaria dauci and Cercospora carotae) severity, canopy microclimate, and total and marketable yield were assessed. The number of apothecia of S. sclerotiorum and relative humidity in the canopy were reduced by trimming done at either the first observation of apothecia or at 100 days after seeding (DAS). In both cases, the effects of trimming on canopy microclimate lasted between 2 and 4 weeks. Trimming the canopy twice during the season did not reduce the number of apothecia compared with trimming the canopy once at 100 DAS. Foliar trimming had little effect on CLB severity. This was attributed mainly to the lower requirement of the CLB pathogens for prolonged periods of high relative humidity and leaf wetness compared with S. sclerotiorum. Foliar trimming did not improve the efficacy of fungicide applications for CLB control. Trimming the canopy once or twice had no effect on total or marketable yield. Thus, trimming has potential to improve the management of Sclerotinia rot of carrot, and trimming both at first observation of apothecia and at 100 DAS could reduce apothecia production and relative humidity within the canopy.

Resistências cruzadas em biótipos de Alisma Plantago-Aquatica resistentes ao bensulfurão-metilo e suas consequências

The repetitive use of bensulfuron-methyl in rice fields from Sorraia, Sado and Mondego river valleys had selected resistant (R) populations of Alisma plantago-aquatica in Portugal, identified as So306, So307, Sa88, Mo190; Mo260, respectively. The response of R-biotypes to bensulfuron-methyl at 26 days after seeding (DAS) and 42 DAS and the crossresistance either to ALS- inhibitors or to herbicides with other mode of action, was investigated in dose-response experiments. The results confirmed bensulfuron-methyl resistance in four biotypes, but not in Mo190, which had been also treated with bentazon every year. Younger plants (6 linear phyllodium, BBCH 116) were more susceptible to bensulfuron-merthyl than were older plants (6 expanded phyllodium, BBCH 126). R-biotypes presented cross-resistance to all ALS-inhibitors studied except for imazethapyr and metsulfuron-methyl. Resistance indeces (RI= ED 50R /ED50 S) ranged frome 3 to 313 for the three sulfonylurea herbicides. Herbicides with different mode of action including bentazon, MCPA, oxadiazon and propanil showed resistance indices of one, indicating that all herbicides tested had equal activity to both Rand S-biotypes. It was concluded that these herbicides could be effective for the control of resistant A. plantago-aquatica biotypes in rice paddy fields.

Crescimento e desenvolvimento de cinco espécies de plantas daninhas do gênero Amaranthus

O objetivo deste trabalho foi analisar o crescimento e o desenvolvimento de cinco plantas daninhas do gênero Amaranthus, em condições não-competitivas. As espécies estudadas foram: A. deflexus, A. hybridus, A. retroflexus, A. spinosus e A. viridis. Foram realizadas oito avaliações periódicas de crescimento, espaçadas em 10 dias, iniciando-se aos 20 dias após semeadura (DAS). As variáveis avaliadas por planta foram: área foliar, massa seca das raízes, ramos, folhas, flores + frutos e total; obtendo-se, a partir desta última, as taxas de crescimento absoluto e relativo. Também foram avaliadas as etapas fenológicas de desenvolvimento das plantas. A. deflexus foi a espécie com ciclo vegetativo mais curto, menor acúmulo de massa seca e área foliar. Por outro lado, A. retroflexus e A. hybridus foram as que alcançaram os maiores valores para essas variáveis. A. viridis foi a de melhor adaptabilidade ecológica para as condições em que o experimento foi desenvolvido, pois, além de acumular grande quantidade de massa seca e área foliar, observaram-se rápido desenvolvimento vegetativo e crescimento absoluto. Esses resultados sugerem que A. viridis é uma espécie com alto potencial de interferência nas culturas agrícolas, proporcionado pelo uso eficiente dos recursos de crescimento fornecidos pelo ambiente durante os estádios iniciais de crescimento.

Use of Cyclic Voltammetry, Photochemiluminescence, and Spectrophotometric Methods for the Measurement of the Antioxidant Capacity of Buckwheat Sprouts

This paper describes the use of cyclic voltammetry, photochemiluminescence (PCL), and spectrophotometric methods (TEAC and FCR reducing capacity) for the measurement of the antioxidant capacity of dark- and light-grown buckwheat sprouts. Moreover, the flavonoid profile of studied material is provided. Methanol extracts (80%) from ungerminated buckwheat grain and 6 and 8 DAS (days after seeding) sprouts were used. The 8 day germination period was sufficient to obtain good quality sprouts with completely removed pericarps. The ungerminated buckwheat grain contained only rutin, whereas in sprouts produced in dark or light, a high level of isoorientin, orientin, vitexin, rutin, and isovitexin was found. The flavonoid content in sprouts produced under light was almost 2 times higher than those of sprouts produced in the dark. The antioxidant capacity of light-grown sprouts was higher than that of dark-grown ones. The results from voltammetric experiments obtained for buckwheat seeds and 6 and 8 DAS sprouts harvested under dark or light conditions highly correlated with those obtained by PCL antioxidant capacity of water-soluble substances (PCL ACW) (r = 0.99), PCL antioxidant capacity of lipid-soluble substances (r = 0.99), TEAC (r = 0.99), and FCR reducing capacity (r = 0.99). The use of cyclic voltammetry, PCL ACW, and TEAC was fully applicable for the evaluation of the antioxidant capacity of buckwheat sprouts.

Acúmulo de macronutrientes pela cultivar de cebola "Superex" estabelecida por semeadura direta

O objetivo do trabalho foi quantificar o acúmulo de macronutrientes ao longo do ciclo da cebola, cv. "Superex", estabelecida por semeadura direta. O experimento foi conduzido na Fazenda Rio Doce, entre os municípios de Itobi e São José do Rio Pardo, SP. As amostragens de plantas foram realizadas aos 30, 50, 70, 90, 110, 130 e 150 dias após a semeadura (DAS), para determinação da matéria seca e do acúmulo dos nutrientes (N, P, K, Ca, Mg e S). Os acúmulos máximos de matéria seca da parte aérea e do bulbo foram, respectivamente, de 4,70g planta-1 e 17,86g planta-1, aos 150 DAS. A parte aérea e o bulbo contribuíram, respectivamente, com cerca de 20 e 80% na matéria seca da planta inteira ao final do ciclo. A seqüência de acúmulo dos nutrientes verificada para a cebola "Superex" foi: K>N>Ca>S>Mg>P. A planta de cebola acumulou 202,43; 31,23; 295,28; 172,42; 35,20 e 73,47mg, respectivamente, de N, P, K, Ca, Mg e S. Exportou, pelo bulbo, 67% do N, 85% do P, 68% do K, 57% do Ca, 56% do Mg e 81% do S acumulado pela planta.

Caracterização do enraizamento da beterraba sacarina (Beta vulgaris L.) num solo de aluvião

Knowledge of plant rooting patterns and their evolution during the crop season is important for the apropriate soil water and nutrients management. The implementation of efficient irrigation practices – such as the irrigation management in real time for a certain area – needs information on meteorological, soil and crop parameters: such as crop growth stage, crop coefficients, paths of rooting depth, crop sensitivity to water stress, allowable soil water deficit, etc. Also, the characteristics of irrigation events should also be known, normally irrigation amount, opportunity, and evaluation. The objective of the present study is to evaluate a sugar beet crop growth including root growth pattern, on an Alluvial soil, under irrigation to give the crop the optimum water amount for maximum growth. The minirizotron method was used for monitoring root growth during crop season. Later on, trenches were opened for directly observing and measuring root development and pattern, up to 50 cm depth. Beet root depth and weight were evaluated at several points – growing stage from 0 to 69 days after seeding (DAS), yield formation from 69 to 166 DAS, and ripening from 166 to 196 DAS - and crop growth indices were also determined: leaf area index (LAI), and the duration of crop growing stages. Finally, biomass and grain production were evaluated. Data obtained showed that: 1) Maximum values for biomass and LAI were observed at 96 to 111 days, the values decreasing afterwards, while leaf senescence and rapid root growth occurred; and 2) Mass and depth of the beet root was observed to increase throughout the crop cicle, but faster between 96 and 111 DAS, reaching 2000 g and 40 cm respectively at 196 DAS. Images obtained with the minirizotron showed that fine beet roots had grown down to 90 cm depth.

Regulation of polyunsaturated fatty acids accumulation and characterization of linolenic acid after germination of sunflower seed

The metabolism of triacylglycerols (TAG) and their conversion into new triglycerides and polar lipids such as linolenic acid take place during the first phase of development of Helianthus annuus L. seed after seeding. Oleate desaturase and linoleate desaturase are two major enzymes responsible for the synthesis of these compounds. To determine whether enzymatic mechanisms function the same in catabolizing seed store lipids of normal and mutant sunflower lines, modifications of fatty acids composition of seeds and the initial stages of growth (seeding-VE) cultivated under conditions of controlled temperature were assessed. The increase of linoleic acid content during all stages of development in a mutant line revealed a higher activity of oleic acid desaturase (Δ12-desaturase) in transforming oleic acid to linoleic acid probably due to higher availability of the substrate of this enzyme in this line; however, its amount increased moderately in a normal line. The activity of FAD2-3 in developing sunflower seeds is recognized even two days after seeding (DAS) in both lines; however, linolenic acid accumulation starts seven DAS.

Seasonal Nitrogen Partitioning and Nitrogen Uptake of Carrots as Affected by Nitrogen Application in a Mineral and an Organic Soil

An understanding of nitrogen (N) uptake and the partitioning of N during the season by the carrot crop (Daucus carota subsp. sativus [Hoffm.] Arkang.) is required to develop more efficient N fertilization practices. Experiments were conducted on both organic and mineral soils to track the accumulation of dry matter (DM) and N over the growing season and to develop an N budget of the crop. Treatments included two carrot cultivars (`Idaho' and `Fontana') and 5 N rates ranging from 0% to 200% of the provincial recommendations in Ontario. Foliage and root samples were collected biweekly from selected treatments during the growing season and assessed for total N concentration. Harvest samples were used to calculate N uptake, N in debris, and net N removal values. Accumulation of DM and N in the roots was low until 50 to 60 days after seeding (DAS) and then increased linearly until harvest for all 3 years regardless of the soil type, cultivar, and N rate. Foliage dry weight and N accumulation were more significant by 50 to 60 DAS, increased linearly between 50 and 100 DAS, and reached a maximum or declined slightly beyond 100 DAS in most cases. The N application rates required to maximize yield on mineral soil resulted in a net loss of N from the system, except when sufficient N was available from the soil to produce optimal yield. On organic soil, a net removal of N occurred at all N application rates in all years. Carrots could be used as an N catch crop to reduce N losses in a vegetable rotation in conditions of high soil residual N, thereby improving the N use efficiency (NUE) of the crop rotation.

Evaluation of mulching, intercropping with Sesbania and herbicide use for weed management in dry-seeded rice ( Oryza sativa L.)

This study was conducted to evaluate the effects of intercropping Sesbania with dry-seeded rice up to its vegetative phase ( Sesbania), mulching with wheat residue (mulch) and herbicides for managing weeds and optimising the yield of dry-seeded rice. The density of grass weeds was lower with the mulch at all stages of crop growth. Though the dry weight of grass weeds at 30 days after seeding (DAS) was lower with Sesbania than with mulch, they were similar at later stages. A lower broadleaved weed density and dry weight were observed with Sesbania than with the mulch. It is concluded that application of wheat residue mulch at 4 t ha –1 and Sesbania intercropping for 30 days were equally effective in controlling weeds associated with dry-seeded rice. However, pendimethalin (1000 g a.i. ha –1) or pretilachlor with safener (500 g a.i. ha –1) as pre-emergence applications followed by one hand-weeding were effective in controlling weeds, increasing grain yield of dry-seeded rice, and resulting in higher net returns than the weed-free treatment.

Effect of Natural Light Periods on Rutin, Free Amino Acid and Vitamin C Contents in the Sprouts of Common (Fagopyrum esculentum Moench) and Tartary (F. tataricum Gaertn.) Buckwheats

Contents of rutin, free amino acids and vitamin C were measured with the sprouts of common buckwheat (Fagopyrum esculentum Moench, FE) and tartary buckwheat (F. tataricum Gaertn., FT), cultivated in darkness and/or under natural light conditions. Flavonoids, including rutin and quercetin were isolated from the sprouts of FE and FT by using HPLC and quantified with their authentic standard compounds. In FE sprouts, rutin content placed under natural light conditions was higher than from plants grown in darkness. In contrast, in FT sprouts rutin content was significantly affected both by days after seeding (DAS) and by lighting. On average, rutin content (55mg/g dry weight) of FT sprouts was 2.2-fold higher than that of FE sprouts. In both species, free amino acids levels were increased with increased natural light periods, and vitamin C content of the sprouts cultivated in darkness in both species was significantly lower than that of light-grown sprouts. Based on these characteristics, we concluded that the green sprouts of FT are a superior source of rutin, free amino acids and vitamin C. They could therefore be used as ‘functional foods’ fresh vegetables and freeze-dried powder.

Weed management in dry-seeded rice ( Oryza sativa) cultivated in the furrow-irrigated raised-bed planting system

Dry seeding of rice ( Oryza sativa L.) in the furrow-irrigated raised-bed planting system (FIRBS) represents a major shift in the production practices for attaining optimal water productivity in the rice–wheat system in the Indo-Gangetic Plains of South Asia. Information on weed management in dry-seeded rice in the FIRBS is lacking. Two experiments were conducted for 2 years, with an objective of identifying appropriate, effective, and economical methods of managing: (1) broadleaf weeds only; and (2) a mixed population of both grass and broadleaf weeds in dry-seeded rice cultivated in the FIRBS. The major weeds associated with dry-seeded rice in the FIRBS during both years were Echinochloa crus-galli (L.) P. Beauv., Echinochloa colona (L.) Link, Dactyloctenium aegyptium (L.) Willd., Leptochloa panicea (Retz.) Ohwl, Caesulia axillaris Roxb., Euphorbia hirta L., Lindernia sp., Commelina benghalensis L., Eclipta prostrata (L.) L., Trianthema portulacastrum L., and Portulaca oleracea L. Triclopyr at 500 g a.i. ha −1, bensulfuron at 60 g a.i. ha –1, ethoxysulfuron at 18 g a.i. ha –1, and 2,4-D (ester) at 500 g a.i. ha –1, all applied at 21 days after seeding (DAS), were equally effective in realizing higher rice grain yields by controlling broadleaf weeds. Among these, ethoxysulfuron at 18 g a.i. ha –1 was found to be least expensive but effective for controlling broadleaf weeds. Effective and economical herbicides identified for managing a mixed population of both grass and broadleaf weeds included fenoxaprop- p-ethyl+ethoxysulfuron at 50+18 g a.i ha –1, applied at 21 DAS, and pendimethalin followed by (fb) chlorimuron+metsulfuron at 1000 fb 4 g a.i. ha −1 applied at 3 fb 21 DAS.

Effect of Cowpea severe mosaic virus on Crop Growth Characteristics and Yield of Cowpea.

Field experiments were carried out in St. Augustine, Trinidad & Tobago, West Indies to determine the effects of time of inoculation of Cowpea severe mosaic virus (CPSMV) and cultivar on crop growth and yield in cowpea (Vigna unguiculata). Crop growth and yield loss were investigated through growth analysis and yield component analysis on three cultivars in two seasons (wet and dry). Time of inoculation had the most profound impact on yield. Inoculations during the early log phase (seedling stage), 12 days after seeding (DAS), consistently had the greatest impact (50 to 85% yield loss) compared with those inoculated during the exponential growth phase (24 DAS; 22 to 66% yield loss) or linear growth phase (35 DAS; 2 to 36% yield loss). The effects were particularly pronounced in the dry season and in the more determinate cultivar, H8-8-27. Reduction in maximum leaf area index, leaf area duration, or maximum vegetative dry matter explained reductions in yield. Yield reductions resulted primarily from reduced pod number per plant and, to a lesser extent, from reduced average pod dry weight. The results show that CPSMV control measures should be aimed at delaying infection by CPSMV to minimize the impact on cowpea yield.

Effect of plastic mulch and row covers on photosynthesis and yield of watermelon

The effect of row covers on watermelon (Citrullus vulgaris) grown on plastic mulch is well documented. However, row covers have not been adequately evaluated under Mexican growing conditions. Watermelon plants were grown on plastic mulch alone or with row covers to study their effect on photosynthesis, and early and total yields. Treatments were clear plastic mulch (C); black plastic mulch (B); B plus a Vispore cover of polypropylene (BV); B plus a white cover of perforated polyethylene (BW); B plus a clear cover of perforated polyethylene (BC); B plus an Agribon cover of polypropylene (BA); and bare soil as the control. For plants grown in treatment C, B or B combined with row covers, plant dry weight and number of leaves 40 days after seeding (DAS) were higher than the control (P<0.05), except BC which was comparable to the control. Total yields of treatments C, B, BV, BW and BA differed (P<0.05) from BC and the control. Total yields increased by 46.1, 43.2, 35.7, 41.6, 13.3, 15.4 and 35.8 t/ha for the C, B, BV, BW, BC and BA treatments, respectively, over the control, which yielded 27.1 t/ha. Total yield was highest for the C and the B treatment suggesting that there was no need for additional covers. The number of leaves per plant or dry weight per plant better explains the changes in yield than net photosynthesis rate. Stomatal conductance was explained in part by changes in photosynthesis.

Renovating Golf Course Fairways with Zoysiagrass Seed

Zoysiagrass (Zoysia japonica Steud.) requires few inputs and provides high-quality turf in the transition zone, but is expensive to sprig or sod. Establishment by seed is less expensive than vegetative establishment, but little is known about renovation of existing turf to zoysiagrass using seed. Two experiments were performed to determine effects of herbicides and seeding rates on establishment of zoysiagrass in Indiana and Kentucky. In the first experiment, interseeding zoysiagrass into existing perennial ryegrass (Lolium perenne L.) without the use of glyphosate before seeding resulted in 2% zoysiagrass coverage 120 days after seeding (DAS). In plots receiving glyphosate before seeding, zoysiagrass coverage reached 100% by 120 DAS. In the second experiment, MSMA + dithiopyr applied 14 days after emergence (DAE) or MSMA applied at 14+28+42 DAE provided the best control of annual grassy weeds and the greatest amount of zoysiagrass establishment. Applying MSMA + dithiopyr 14 DAE provided 7% less zoysiagrass coverage compared to MSMA applied 14 DAE at one of the four locations. Increasing the seeding rate from 49 kg·ha-1 to 98 kg·ha-1 provided 3% to 11% more zoysiagrass coverage by the end of the growing season at 3 of 4 locations. Successful zoysiagrass establishment in the transition zone is most dependent on adequate control of existing turf using glyphosate before seeding and applications of MSMA at 14+28+42 DAE, but establishment is only marginally dependent on seeding rates greater than 49 kg·ha-1. Chemical names used: N-(phosphonomethyl) glycine (glyphosate); monosodium methanearsenate (MSMA); S,S-dimethyl 2-(difluoromethyl)-4-(2-methylpropyl)-6-(triflurormethyl)-3,5-pyridinedicarbothioate (dithiopyr).

Soil Amendments and Fertilizer Source Effects on Creeping Bentgrass Establishment, Soil Microbial Activity, Thatch, and Disease

Natural organic fertilizers require microbial degradation for nitrogen (N) release, but their ability to promote rapid turfgrass establishment has not been well documented in newly constructed sand-based rootzones. This 2-year field study evaluated the influence of two general fertilizer and soil amendment programs for their effect on establishment and quality of three creeping bentgrass (Agrostis stolonifera L.) cultivars—`Crenshaw', `Penn G-2', and `Providence'. Turf was grown on a 4 sand: 1 sphagnum peat (by volume) rootzone mixture. Four treatments consisting of surface-applied synthetic fertilizer (SF; mostly water-soluble N in 1999 and methylene urea thereafter); surface-applied hydrolyzed poultry meal (PM); preplant-incorporated granular humate (GH) with surface-applied SF; and preplant-incorporated PM with surface-applied PM. Turf cover data collected 42 days after seeding (DAS) showed that the rate of establishment was SF+GH incorporated = SF surface-applied >PM surface-applied + PM incorporated >PM surface-applied. Turf cover was ≥96% among all treatments 90 DAS. Rootmass density was greater (18% to 29%) at 103 DAS in GH incorporated plots combined with SF, when compared to all other treatments, but no rootmass differences subsequently were observed. Soil microbial activity generally was highest in PM-treated plots during the first 14 months following seeding, but not thereafter. Turf treated with SF had less microdochium patch (Microdochium nivale (Fr.) Samuels and I.C. Hallett) and more bentgrass dead spot (Ophiosphaerella agrostis Dernoeden, M.P.S. Camara, N.R. O'Neill, van Berkum et M.E. Palm), when compared to PM-treated plots. Slightly less thatch developed in PM-treated turf when compared to plots receiving SF alone by the end of the second year. Penn G-2 and SF generally provided the best overall turf quality. This study demonstrated the beneficial effects of readily available N from SF for rapid establishment and that preplant incorporation of GH initially aided root development.