Expansion volume, defined as the volume of popped corn per gram of unpopped corn, is considered the most important quality trait in popcorn (Zea mays L.). The increasing popularity of microwave popcorn has necessitated the development of cultivars for use in both conventional and microwave popping. Information on expansion volume of popcorn genotypes using both popping methods is not available in the literature. This study investigated the presence of a genotype ✕ popping method interaction for expansion volume and its components in popcorn. Eleven commercial popcorn hybrids, one flint corn ✕ popcorn inbred line cross, and one open‐pollinated popcorn variety were grown in isolation in 1988. Seed harvested from each genotype was divided equally into large‐ and small‐kernel samples that were evaluated for expansion volume, popped kernel (flake) size, and percent unpopped kernels in conventional and microwave popping. All genotypes performed better in conventional popping than in microwave popping. Significant differences existed among genotypes for expansion volume and flake size. A significant genotype ✕ popping method interaction was detected for expansion volume, flake size, and percent unpopped kernels. Therefore, breeders utilizing germplasm similar to that which we studied with the dual objective of developing cultivars for conventional and microwave popcorn markets should conduct evaluations for expansion volume using both popping methods.

Four cultivars (Blitz, Mariachi, Quest and Rapsodie) of tomato were grown hydroponically on rockwool in two microclimates (east and west) inside the greenhouse (Tucson, AZ) under two nutrient solution electrical conductivity (EC) levels (2.6 or 4.5 dS m-1), adjusted by adding NaCl and CaCl 2 after the setting of first fruit truss. In all cultivars, total soluble solid (TSS, %Brix at 20 o C) and lycopene concentration of fruits increased by 12-23 % and 34-85 %, respectively, with increasing EC level. Fruits harvested from the east side of the greenhouse had higher TSS than those from the west side, due to the different plant microclimate varying by daily PPF (photosynthetic photon flux) and VPD (vapor pressure deficit). However, lycopene concentration in fruits was not significantly affected by plant microclimate regardless of cultivars or EC. The cultivar of Mariachi showed the strongest effect in response to nutrient solution EC levels regarding both TSS and lycopene concentration among the cultivars examined. The cumulative yield at 7 weeks showed no significant differences between nutrient solution EC and locations, regardless of cultivars. The results indicated that value added tomato fruits could be produced by manipulating EC and plant microclimate in the greenhouse without causing yield reduction.

Fresh parboiled rice hulls ground in a hammer mill and screened through a 1.18-mm screen and collected on a 0.18-mm screen (RH3) and particles with a specific diameter of 0.5 to 1.0 mm had total pore space (TPS), air-filled pore space (AFP), and water-holding capacity (WHC) similar to that of Canadian sphagnum peat (peat). However, RH3 had more available water, a higher bulk density (BD), and a higher particle density (PD) than peat. When blended with 20% to 40% perlite or 1 cm aged pine bark, RH3-based substrates had lower TPS, similar AFP, and lower WHC than equivalent peat-based substrates. The RH3-containing substrates had higher BD and average PD than equivalent peat-based substrates. When blended with parboiled rice hulls (PBH), RH3-based substrates had lower TPS than equivalent peat-based substrates. When blended with 20% to 40% PBH, RH3-based substrates had lower AFP than equivalent peat-based substrates. RH3-based substrates containing up to 20% PBH had lower WHC than equivalent peat-based substrates. RH3-based substrates containing 40% PBH had a higher WHC than equivalent peat-based substrates. When blended with PBH, all RH3-based substrates had higher BD and average PD than equivalent peat-based substrates. The addition of 40% RH3 to a peat-based substrate containing 20% perlite decreased substrate TPS, whereas the addition of 10% to 40% decreased AFP. The addition of 10% to 30% RH3 increased WHC. The addition of 30% RH3 to a peat-based substrate containing 20% 1 cm aged pine bark decreased substrate TPS and the addition of 20% to 40% RH3 decreased AFP. The addition of 10% RH3 increased WHC, but the addition of 20% or more RH3 did not affect WHC. The addition of 30% RH3 increased the BD, but the addition of RH3 had no effect on average PD. The addition of 20% or more and 30% or more RH3 to a peat-based substrate containing 20% PBH decreased substrate TPS and AFP, respectively. The addition 20% RH3 decreased WHC. The addition of 10% to 40% RH3 increased BD. Overall, RH3 was the ground rice hull product that had physical properties most similar to peat. Peat-based substrates in which up to 40% of the peat was replaced with RH3 had physical properties that, although different from peat controls, were within commonly recommended ranges for substrates used to grow greenhouse crops.

The primary objective of this research was to compare the pH, electrical conductivity (EC), and primary macronutrient status of three ground parboiled fresh rice hull (PBH) products to sphagnum peat when used as a root substrate over 56 days in a greenhouse environment. The three grades of ground rice hull products were produced by grinding PBH and passing the ground product through different screens. One grade (P3) was passed through a 2.00-mm screen and captured on a 1.00-mm screen. The second grade (P4) was passed through a 1.00-mm screen and captured on 0.50-mm screen. A third ground rice hull product (RH3) was a commercially available, ground PBH material that was ground in a hammer mill until it passed through a screen with 1.18-mm-diameter openings and was collected on a screen with 0.18-mm openings. The pH of sphagnum peat ranged from 3.4 to 3.7 across time. The pH of RH3 and P3 increased from 4.7 to 7.1 on day 5 and 14, respectively, before decreasing to 6.3 and 6.7, respectively, on day 56. The pH of P4 increased from 4.8 to 6.9 on day 6 before decreasing to 6.6 on day 56. The P4 had an EC of 1.2 dS·m−1, which was higher than that of peat, RH3, and P3, which had similar EC of 0.7 to 0.8 dS·m−1 regardless of time. The ammonium (NH4+) concentration was unaffected by time. Peat had an NH4+ concentration of 6.4 mg·L−1, which was lower than that of the ground rice hull products. The P3 had an NH4+ concentration of 14.6 mg·L−1, which was higher than that of RH3 and P4. The RH3 and P4 had similar NH4+ concentrations of 11.8 and 10.8 mg·L−1, respectively. The nitrate (NO3−) concentration was unaffected by time. The RH3 had a NO3− concentration of 8.2 mg·L−1, which was significantly higher than that of peat, P3, and P4, which had similar NO3− concentrations of 0.5 mg·L−1. The phosphorus (P) concentration in peat ranged from 1.3 to 2.5 mg·L−1 across the sampling times, and peat had a lower P concentration than all rice hull products, which ranged from 57.4 to 104.4 mg·L−1. The potassium (K) concentration in peat ranged from 2 to 5 mg·L−1 across the sampling times and was always lower than that of the rice hull products, which had a K concentration ranging from 195 to 394 mg·L−1. Because pH, P, and K concentrations were above recommended concentrations, ground rice hull products would not be suitable as a stand-alone substrate but might be amended with materials such as elemental sulfur or iron sulfate to adjust the pH or blended with other components to reduce the P and K concentrations to within recommended concentrations.

Cherry tomato (Solanum lycopersicum var. cerasiforme) plants were grown hydroponically with three different regimes of electrical conductivity (EC) of the nutrient solution to develop an effective EC management method to enhance the fruit quality. The EC treatments examined were 1) continuous high EC [4.7 dS·m−1 (HE)], 2) continuous low EC [2.8 dS·m−1 (LE)], and 3) high EC combined with midday (1030–1530 hr) low EC [midday reduction of high EC (MDR)]. The research was conducted to obtain preliminary information on the effect of EC treatments on the yield and fruit quality for 15 weeks of harvest under semiarid greenhouse conditions. Harvested fruit were sorted to several quality grades, including the “premium” grade based on fruit size, color, and total soluble solids. The number of fruit per truss was significantly higher in cultivar L308 than in cultivar L907 and in the LE treatment than in the HE or MDR treatment. The fruit size decreased over time regardless of EC treatment and cultivar. Cumulative yield of 15 weeks was greater in the LE treatment (26.3 kg·m−2) than in the HE treatment (22.1 kg·m−2) for ‘L907’, and there were no significant differences between the three EC treatments for ‘L308’ (24.1–28.1 kg·m−2). The cumulative yield in the MDR treatment was similar to that in the LE treatment regardless of cultivar. When quality attributes such as total soluble solids concentration measured for randomly sampled fruit were considered, cumulative premium-grade yield was the greatest for the HE treatment (12.9 or 17.6 kg·m−2) and was the smallest for the LE treatment (1.4 or 12.1 kg·m−2), regardless of cultivar. The cumulative yield of premium-grade cherry tomatoes in the MDR treatment was not significantly different from that in the HE treatment for ‘L308’ but was 11% less than that in the HE treatment for ‘L907’. Therefore, together with cultivar selection, the MDR treatment may be a potential alternative to a more commonly practiced continuously high EC treatment in semiarid greenhouses with limited environmental control capacity in which increasing the nutrient EC to increase quality is desired without significantly decreasing yield.