Search Results

You are looking at 1 - 10 of 10 items for

  • Author or Editor: A.R. Mitchell x
Clear All Modify Search
Authors: and

Furrow irrigation of peppermint (Mentha piperita L.) has certain benefits over sprinkler irrigation, but usually wastes irrigation water. Alternate-furrow irrigation allows frequent application of small amounts of water, which is an advantage over conventional furrow irrigation. In a variation of alternate-furrow irrigation, alternating-furrow irrigation, every other furrow is irrigated at the first irrigation, and the remainder at the second, then this procedure is repeated throughout the season. It is a low-cost, low-energy alternative to sprinkler and center pivot irrigation systems. Our objective was to compare yield and water use of alternating-furrow irrigation with those of conventional every-furrow irrigation for peppermint. Field experiments in 1992 and 1993 indicated that the soil water content was adequate under both irrigation treatments, and the water savings for alternating-furrow irrigation were attributed to less runoff and less evaporation from the soil surface. There was no difference in yield between the systems, although alternating-furrow irrigation required about half of the water applied with the conventional treatment. One limitation of alternating-furrow irrigation occurred near the end of the growing season, when the plants lodged, partially dammed the furrow streams, and made timely furrow advance difficult. This problem was resolved by irrigating every furrow after lodging occurred.

Free access

Rice (Oryza sativa L.) is a candidate crop for use in Controlled Ecological Life-support Systems (CELSS) proposed for a lunar or Mars outpost. `Ai-Nan-Tsao' is a promising semi-dwarf cultivar because growth volume is limited and HI (percent edible biomass) is high. Yield efficiency rate (YER: g grain/m3 per day [g nonedible biomass]-) combines edible yield rate (EYR: g grain/m3 per day) and HI to quantify edible yield in terms of penalties for growth volume, cropping time, and nonedible biomass production. Greenhouse studies indicate EYR increases with plant density from 70 to 282 plants/m2. YER and shoot HI are stable across this density range because nonedible biomass accumulation keeps pace with edible. Tiller number and panicle size per plant decreased with increasing plant density, but total tiller and panicle number per unit area increased to compensate. Density trials in rigorously controlled environments will determine if higher plant densities will produce even greater YER. This research is supported by NASA grant NAGW-2329.

Free access

Mineral resources will be recycled in a controlled ecological life-support system (CELSS) deployed in space. N typically is supplied to crops as NO 3 or NH 4 + + NO 3 mixtures. In a CELSS, NH 4 + will be abundant, but nitrification will require energetically costly chemical or biological NH 4 + oxidization. Rice is tolerant of NH 4 + and preferentially absorbs NH 4 + if provided a 1 NO 3 : 1 NH 4 + ratio in hydroponics. Hybrid rice absorbs more N as NH 4 + than does inbred rice. To determine how much and in what proportion to NO 3 rice will tolerate NH 4 + and how varying N sources will affect grain yield, semi-dwarf hybrid rice cultivar `Ai-Nan-Tsao' was grown hydroponically in a growth chamber. Nutrient solutions supplied 5 mm N as 40%, 60%, or 80% NH 4 + , the remainder as NO 3 . Periodic analysis of solutions tracked mineral uptake, and solutions were modified to maintain proper concentrations. Treatment stands were harvested 84 to 86 DAP. Across all treatments, yield characteristics were similar but were highest for the border plants, presumably due to greater light absorption. Yield-efficiency rate (YER: grams of grain·per cubed meter per day·[grams inedible shoot biomass]) was 0.09 for all treatments (border) and ranged from 0.03 to 0.05 (interior), Harvest index ranged from 0.28 to 0.30 (border) and 0.26 to 0.39 (interior). Edible yield rate (EYR: grams of grain per cubed meter per day) ranged from 20.97 to 26.45 (border) and 8.52 to 14.96 (interior). The sector provided with 80% NH 4 + had the highest YER, HI (interior), and EYR (interior), indicating that rice productivity was not limited by high percentages of N supplied as NH 4 + . Supported by NASA grant NAGW-2329.

Free access

Because peppermint (Mentha piperita L.) grows anew from rhizomes each spring, methods to measure the energy stored in the peppermint rhizomes would be useful. Our objective was to compare three methods of measuring carbohydrate in peppermint samples taken throughout a growing season. Total nonstructural carbohydrate (TNC) is a measure of the water- and acid-soluble sugars. Etiolated growth measurements of nonstructural biomass (NSB) are a reliable method for alfalfa (Medicago sativa L.) taproots. Near infrared spectroscopy (NIRS) is another method that has been used to determine TNC of alfalfa. Rhizomes were sampled monthly from four locations within a field. The NSB was correlated (r = 0.74) with the TNC means from each sampling date. The NIRS calibration was highly correlated with the TNC of all samples (R 2=0.96). Both NSB and TNC decreased in summer and increased in the fall as the plant stored carbohydrate for winter survival and regrowth. Any of the three methods could be used to study energy storage, although NIRS is the quickest, and NSB the least technologically sophisticated. Based on the positive results of NIRS, a more comprehensive calibration is warranted.

Free access

Abstract

Red maple (Acer rubrum L.) and baldcypress (Taxodium distichum (L.) Rich.) seedlings were very tolerant of extended flooding, whereas shoots of sugar maple (Acer saccharum Marsh) seedlings experienced desiccation after 8 days of flooding, and leaf death after 14 days. Shoot desiccation occurred after 14 days of flooding. Roots of all 3 species utilized O2 with similar efficiency prior to flood stress. However, the respiratory capacity of sugar maple roots declined substantially during the first 8 days of flooding, and more gradually from 8 to 22 days, at 21, 5, or 0.5% O2. Red maple roots declined gradually in respiratory capacity over the entire flooding period at 21 and 5%, but not at 0.5% O2. After an initial sharp decline, baldcypress roots gradually regained capability to utilize O2 from 8 to 22 days of flooding at all 3 levels of O2. When tested at 21% O2, both red maple and baldcypress roots had 2- to 3-fold higher respiratory capacities than did sugar maple roots after 22 days of flooding. Presoaking root sections from flooded red and sugar maple in a sucrose solution mildly stimulated respiration rates measured at 21% O2, but did not fully restore respiratory capacity lost by flooding either species.

Open Access

Abstract

Effects of cyanide (as KCN) and/or salicylhydroxamic acid (SHAM) on respiratory rates (QO2 ) of excised tree roots were evaluated before and after flooding intact plants. CN, an inhibitor of cytochrome oxidase, stimulated QO2 in flood-intolerant sugar maple (Acer saccharum Marsh.) and Japanese yew (Taxus cuspidata Sieb. and Zucc.), but not in flood-tolerant red maple (Acer rub rum L.), and inhibited QO2 in very flood-tolerant baldcypress (Taxodium distichum (L.) Rich). Eight days of flooding eliminated CN-stimulation of QO2 in sugar maple. SHAM, an inhibitor of the alternative oxidase, had little effect on QO2 of any species when used alone, but greatly inhibited QO2 of all species when combined with KCN, indicating the presence of substantial amounts of both respiratory pathways in flood-tolerant and intolerant species, as well as the ability of electrons to flow from one pathway to another when one is blocked by a specific inhibitor. Flooding reduced root respiration capacity in all species, affecting intolerant species the most and tolerant the least. The exception was QO2 of dormant Taxus roots, which was not inhibited by flooding. CN-sensitive QO2 was lost from roots of intolerant species in particular, and to a lesser extent from more tolerant species. A limiting leveL of O2 (0.5%) suppressed SHAM-sensitive QO2 more than CN-sensitive QO2 indicating a greater affinity for O2 by the CN-sensitive path-way. The evidence is consistent with a model for relative flood tolerance based upon differential damage to the aerobic respiratory mechanism.

Open Access

Previously published research suggests that the yield and water-use efficiency of C-3 plants can be enhanced through foliar-applied methanol. Potatoes (Solanum tuberosum L. cv. Russet Burbank) grown in Oregon at Klamath Falls, Madras, and Ontario were subjected to repeated foliar methanol treatments during the 1993 season. Methanol was applied at 20%, 40%, and 80% concentration with Triton X-100 sticker-spreader at 0.1%, and methanol was applied at 20% and 40% without Triton X-100. Methanol had no effect on tuber yield, size distribution, grade, or specific gravity at any location. Tuber stem-end fry color showed no methanol response at the two locations where it was measured. Soil water potential (measured at Madras and Ontario) showed no difference in water-use efficiency between methanol-treated and nontreated potato plants.

Free access

Abstract

The wide variability in ripeness frequent in ‘Bartlett’ pears at processing can be reduced by prompt, rapid, and uniform warming. Fruits with an initial core temperature of 0.25°C were uniformly warmed to 20° ± 2°C in 30 minutes when air at a rate of 2079 cc/sec/Kg (2 cfm/lb) of product was pulled over them by a modified forced-air tunnel bin warmer operating in a room with an air temperature of 45°C. These fruits ripened in precisely 4 days, with firmness differing between individual fruits by no more than 1.13 Kg (2.5 lb). Conversely, pears warmed at slower rates simulating current cannery procedures varied by as much as a week in time to ripeness.

Open Access

Abstract

Cut carnation flowers shipped from California by air occasionally arrive at eastern markets in a senescent condition with losses greater in the warm autumn months. CO2 and C2H4 production by the flowers has a pattern similar to that of climacteric-class fruits, with senescence correlated with a rise in release of the gases.

Cut carnation flowers show an enormous increase in respiratory heat with increasing temperature: 89 BTU/ton/hour at 0°C versus 14,718 at 50°C. In C2H4-free air, the flowers tolerate elevated temperatures but their vase life is reduced. Their sensitivity to C2H4 increases dramatically with increasing temperature, with the threshold concentration partially depending on prior stresses on the flowers.

Flowers in containers exposed to direct sunlight developed temperatures as high as 49.5°C. Air temperatures inside containers shipped via jet aircraft were as high as 35°C. The C2H4 concentrations in the containers may reach 10.5 ppm.

The remarkable resistance of cut carnation flowers to mechanical injury, combined with their low metabolic rates at low temperatures, makes refrigerated surface shipments feasible and perhaps economically desirable. Their resistance to injury seems related to their light weight, the damping action of the petals, and the lack of phenolase or readily oxidizable phenolic compounds in the petals.

Open Access

The Sustainable Agriculture Farming Systems (SAFS) Project was established in 1988 to study the transition from conventional to low-input and organic farm management in California's Sacramento Valley. We evaluated the effects of these alternative farming systems on soil compaction, water-holding capacity, infiltration, and water storage in relation to tomato yield and fruit quality within the SAFS cropping systems comparison 10 years after it had been established. Soil bulk density (0-15, 15-30, 30-45, and 45-60 cm) was not significantly different among the farming systems. In situ water-holding capacity at 24, 48 and 72 h after water application was significantly higher in the organic system at all times and depths except 45-60 cm. Cumulative water infiltration after 3 h in the organic and low-input cover crop-based plots was more than twice that of the conventional system. The more rapid infiltration in the low-input and organic systems resulted in increased total irrigation needs, more water stored in the soil profile throughout the 30 days before harvest, and lower fruit soluble solids and titratable acidity in these systems relative to the conventional system. Yields were not significantly different in the organic, low-input, and conventional systems during either 1997 or 1998.

Free access