Germination of Myrica pennsylvanicum was increased by exogenous application of kinetin to scarified, cold-stratified seeds. Gibberellic acid (GA3) at 500 and 900 ppm decreased time required for stratification and increased total percentage germination. GA3 was more effective than kinetin for increasing germination.
Seedlings of Lolium multiflorum Lam., Lespedeza stipulacea Maxim., and Bouteloua curtipendula (Michx.) Torr. were grown at 5°C increments between 12° and 37°, 47°, and at alternating temperature regimes of 17°/10°, 25°/18°, 30°/24°, 37°/30°, or 43°/36°. Radicle growth for all species was inhibited at 12° or 17°, and under all alternating temperature cycles. Maximum growth for Lo. multiflorum occurred at 22°, and at 32° for Le. stipulacea and B. curtipendula. No species grew at 47°.
Seeds of Andropogon gerardii Vitman., Panicum virgatum L., Sporobolus heterolepis (A. Gray) A. Gray., Bouteloua gracilis (Willd. ex H.B.K.) Lag ex. Griffiths, Lotus corniculatus L. ‘Empire’, Bromus inermis Leyss., Trifolium hybridum L., Medicago sativa L. Subsp. Sativa ‘Vernal’, and Poa pratensis L. ‘Park’ were pregerminated and grown for 48 hours at 5°C increments between 12° and 37° and at 47°. No radicle growth occurred at 47° for any species. Maximum growth occurred at 27° for B. inermis and 32° for P. virgatum and A. gerardii. For other species, maximum growth occurred over a range of temperatures from 22° to 32°. P. pratensis and B. inermis, C-3 grasses, had no growth but B. gracilis, P. virgatum, and A. gerardii, C-4 grasses, had significant radicle growth at 37°C.
Elaeagnus umbellata (Thunb.) plants were planted in acid soil amended with CaCO3 equivalents of 0.0, 6.6, 13.2, 19.7, 26.4, 52.7, and 102.0 MT/ha of Ca(OH)2 and grown in the greenhouse for 21 months. The pH of the amended soil declined with time. Acetylene reduction rates increased with increasing Ca(OH)2 additions up to 26.4 MT/ha CaCO3 equivalent. The lowest dry matter accumulation in root, stem, leaf and nodule tissue occurred at the lowest pH (3.2) with surviving plants. Dry matter accumulations of leaves, roots and nodules were not statistically different at higher pH values.
Field studies conducted for 2 years showed that glyphosate [N-(phosphonomethyl) glycine] or mixtures of glyphosate and preemergence herbicides applied as preplant and directed postplant sprays were effective in providing season-long weed control in commercial nurseries. Oryzalin [3,5-dinitro-N4,N4-dipropylsulfanilamide] at 2.2 or 4.5 kg ai/ha, and mixtures of simazine [2-chloro-4,6-bis(ethylamino)-s-triazine] at 1.1 kg ai/ha with diphenamid [N,N dimethyl-2,-2-diphenylacetamide] at 6.7 kg ai/ha, napropamide [2-(α-naphthoxyl)-N,N-diethylpropionamide] at 2.2 kg ai/ha, alachlor [2-chloro-2’,6’-diethyl-N-(methoxymethyl) acetanilide] at 2.2 kg ai/ha or oryzalin at 4.5 kg ai/ha were effective treatments when used after preplant application of glyphosate (2.2 kg ai/ha) or when combined with glyphosate (2.2 kg ai/ha). None of the herbicide treatments reduced growth of red maple (Acer rubrum L.), Norway maple (A. platanoides L.), or creeping juniper (Juniperus horizontalis Moench). Japanese spurge (Packysandra terminalis Sieb. and Zucc.) survival was reduced by treatments containing oryzalin.
Three formulations of oxyfluorfen [2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl) benzene], 25% wettable powder (WP), 1% granular (G), 0.24 kg liter-1 emulsifiable concentrate (EC), and 2% G oxadiazon [2-tertbutyl-4(2,4-dichloro-5-isopropoxyphenyl)-Δ2-1,3,4-oxadiazolin-5-one] were compared for weed control and their effects on growth of Cotoneaster apiculatus Rehd. & E.H. Wils., Euonymus fortunei (Turcz.) Hand.-Mazz. ‘Colorata’, and Juniperus horizontalis Moench. ‘Glenmore’. Both herbicides provided acceptable weed control at recommended rates. The EC formulation of oxyfluorfen provided the best weed control, but injury to euonymus and juniper was also most severe with the EC, while injury to cotoneaster was most severe with the EC and G.
Synchronizing the supply of plant-available nitrogen (N) from organic materials with the N needs of apple trees is essential to cost-effective organic apple production. Tree growth and organic matter mineralization are affected by orchard floor management. This study examines the effects of three orchard floor management systems, cultivation, wood chip mulch, and a legume cover crop, on the accumulation and partitioning of compost-derived N in young apple (Malus domestica Borkh.) trees at different compost application dates across two growing seasons. Compost enriched with 15N was applied to apple trees in April, May, and June of 2006 and 2007, and trees were excavated in Sept. 2007 to determine the fate of labeled compost N. Trees with wood chip mulch had significantly greater dry weight and N accumulation in vegetative tree components than trees with cultivation or legume cover. Fruit yields were similar between cultivation and wood chip treatments despite less vegetative growth under cultivation, as these trees partitioned more dry weight into fruit (44%) than wood chip mulch trees (31%). Nitrogen-use efficiency by trees was lower with a living legume cover crop than in other treatments due to competition for resources. In the cover crop aboveground biomass, 20% to 100% of the N was derived from compost. In comparison, only 5% to 40% of N in the decomposing wood chip mulch originated from compost. Tree reserves were an important source of N for spring fruit and leaf growth in all treatments, but significantly more so for trees in the cultivation treatment. Fruit and leaves were strong sinks for compost N early in the season, with trees allocating 72% of spring N uptake into leaves and fruit. In the summer, N uptake increased improving compost N-use efficiency. Summer N was preferentially allocated to perennial tissues (71%), bolstering N reserves. Trees with wood chip mulch performed well and had greater capacity to build N reserves, making wood chips ideal for establishing young organic apple orchards. However, as the orchard matures, it may be beneficial to switch to a groundcover that reduces tree vegetative growth.
This study evaluated the effects of in-row groundcovers (bare ground, brassica seed meal, cultivation, wood chip mulch, legume cover crop, and non-legume cover crop) and three compost rates (48, 101, and 152 kg available nitrogen (N)/ha/year) on soil carbon (C) pools, biological activity, N supply, fruit yield, and tree growth in a newly planted apple (Malus domestica Borkh.) orchard. We used nonlinear regression analysis of C mineralization curves to differentiate C into active and slow soil C pools. Bare ground and cultivation had large active soil C pools, 1.07 and 0.89 g C/kg soil, respectively, but showed little stabilization of C into the slow soil C pool. The use of brassica seed meal resulted in increased soil N supply, the slow soil C pool, and earthworm activity but not total soil C and N, fruit yield, or tree growth. Legume and non-legume cover crops had increased microbial biomass and the slow soil C pool but had lower fruit yield and tree growth than all other groundcovers regardless of compost rate. Soils under wood chip mulch had elevated earthworm activity, total soil C and N, and the slow soil C pool. Wood chip mulch also had the greatest cumulative C mineralization and a high C:N ratio, which resulted in slight N immobilization. Nevertheless, trees in the two wood chip treatments ranked in the top four of the 13 treatments in both fruit yield and tree growth. Wood chip mulch offered the best balance of tree performance and soil quality of all treatments.