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- Author or Editor: Daniel C. Cloutier x
Growth of `Earligold' muskmelon (Cucumis melo L.), expressed as plant dry weight from transplanting to anthesis, could be predicted using a multiple linear regression based on air and soil temperatures for 11 mulch and rowcover combinations. The two independent variables of the regression model consisted of a heat unit formula for air temperatures, with a base temperature of 14C and a maximum reduced threshold of 40C, and a standard growing-degree day formula for soil temperatures with a base temperature of 12C. Based on 2 years of data, 86.5% of the variation in the dry weight (on a log scale) could be predicted with this model. The base temperature for predicting developmental time to anthesis of perfect flowers was established at 6.8C and the thermal time ranged between 335 and 391 degree days in the 2 years of the experiment.
A 2-year study was conducted to assess sweet corn (Zea mays) susceptibility to mechanical weeding using a rotary hoe at preemergence to six-leaf stages of corn development and at different combinations of stages. Three sweet corn cultivars: early (`Quickie'), mid (`July Gem'), and late season (`Sensor') were seeded at two sowing dates. The experiment was conducted in a weed-free environment. In general, sweet corn could be cultivated with the rotary hoe at least once without yield reduction from preemergence to the six-leaf stage. Cob numbers were reduced and maturity delayed after three or four cultivations with the rotary hoe. The rotary hoe could be an effective tool in controlling weeds in an integrated weed management approach or for organic sweet corn production since it cultivates both within and between the rows. The rotary hoe, which covers a large area in a short time, can be used at later growth stages, extending the time period during which it can be used without damaging the crop and reducing yield.
A simple method to predict time from anthesis of perfect flowers to fruit maturity (full slip) and yield is presented here for muskmelon (Cucumis melo L.) grown in a northern climate. Developmental time for individual muskmelons from anthesis to full slip could be predicted from several heat unit formulas, depending on the temperature data set used. When temperature at 7.5 cm above soil level was used, the heat unit formula resulting in the lowest coefficient of variation (cv=6.9%) accumulated daily average temperatures with a base temperature of 11 °C and an upper threshold of 25 °C. With temperatures recorded at a meteorological station located 2 km from the experimental field, the method showing the lowest cv (8.9%) accumulated daily maximum temperatures with a base temperature of 15 °C. This latter method was improved by including a 60-degree-day lag for second cycle fruit. The proportion of fruit volume at full slip of 22 fruit from the first cycle could be described by a common Richards function (R 2=0.99). Although 65% of the plants produced two fruit cycles, fruit from the first cycle represented 72% of total yield in terms of number and mass. The blooming period of productive flowers lasted 34 days, each cycle overlapping and covering an equal period of 19 days. Counting the number of developing fruit >4 cm after 225 degree days from the start of anthesis (when 90% of the plants have at least one blooming perfect flower) could rapidly estimate the number of fruit that will reach maturity.
Auxins, medium salt concentrations, and their interactive effects on rooting of two winter-hardy roses (Rosa kordesii Wulff `John Franklin' and `Champlain') and two hybrid teas (Rosa hybrida `John Paul II' and `Landora') were studied. The auxins (in mg·liter–1) IAA (0, 0.3, 1.5, 3.0, 6.0, or 15.0), IBA (0, 0.1, 0.2, 0.5, 1.0, or 3.0), and NAA (0, 0.1, 0.2, 0.5, 1.0, or 3.0) each were combined factorially with modified Murashige and Skoog (MS) medium (1/4, 1/2, 3/4, and full MS concentrations) and were tested for optimal rooting response. `John Franklin', `John Paul II', and `Landora' rooted well with low or no auxin and medium to high salt concentrations. Optimum rooting for `Champlain' was achieved with high IAA and low salts or with intermediate IBA and NAA concentrations and low to medium salts. The interactive effects of auxins and medium salts for `Champlain' showed that as salt concentration increased, the amount of IBA or NAA required for optimal rooting also increased. The effects of auxins and medium concentrations on root counts per shoot were similar to those for percent rooting. Adding auxin to the medium reduced root length for all cultivars, but salt concentration had a minimal effect. Roots generally were shortest at the highest IBA and NAA concentrations. Salt concentration had little effect on root length. Chemical names used: 1H-indole-3-acetic acid (IAA); 4-(3-indolyl)-butyric acid (IBA); α-naphthaleneacetic acid (NAA).