In Spring 1998, two sweet corn (Zea mays var. rugosa) cultivars were grown under three tillage systems, conventional cultivation, ridge tillage (RT), and no tillage (NT), which had been in continuous management since Fall 1994. Nitrogen (as NH4NO3), the only fertilizer used, was applied twice at 60 kg/ha. Sweet corn yields were not influenced by tillage system, but average ear weights tended to be smaller under NT (P < 0.17). Ear quality attributes, which included ear weight, length, diameter, dry matter, and incidence of earworm damage, were greater in the later-maturing `G-90' cultivar than in `Sensor'; but tillage system had no influence on these attributes. Cultivars supported different weed species underneath their canopies. `Sensor' allowed more light penetration and sustained higher weed biomass than did the taller `G-90' plants. Weed biomass was higher under RT and NT. Seasonal soil moisture was lowest in the RT plots, but only in the 0- to 15-cm profile. Soil temperatures (unreplicated) at the 15-cm depth were similar between cultivars and tillage treatments over the growing season. The earlier-maturing `Sensor' generally accumulated more ear mineral nutrients (P, S, NO3, Ca, Na, Zn, Mn, Al, and B; dry weight basis), but had lower dry matter (percentage) than did `G-90'. Cumulative nutrient levels tended to be lowest in NT-grown ears (P < 0.08). Soil sampled at 0- to 5-, 10- to 15-, and 25- to 30-cm depths generally had higher concentrations of nutrients toward the surface, and NT soils had the steepest nutrient gradients, with the exception of Na and NO3. Total soil salts were reduced by RT and NT, but C: N ratio remained unchanged between tillage systems.
Three-week-old transplants of Amaranthus tricolor cultivars 'RRC 241' (RC) and 'Hinn Choy' (HC) were given split applications of supplemental N of 0, 100 and 200 kg/ha and in the 5th week after sowing were exposed to 100, 70 and 50% of ambient solar radiation for nine and ten days, respectively. Increased shading had a linear (L) effect on leaf blade NO3, protein, K, Mg, S, P, Al, Fe and Cu (dry wt basis). There were L and quadratic (Q) increases in chlorophyll (chloro) and carotenoids. Increasing supplemental N increased leaf blade protein (L,Q), Na (L), Mn (L), chloro (L,Q), carotenoids (L,Q), but decreased Mg (L), P (L,Q) and Zn (L,Q). Nitrate levels showed L and Q increases in RC and HC, respectively. HC was higher in leaf blade K, Mg, Na, Fe, Zn, Cu, NO3, chloro and carotenoides, but lower in CA than RC. Shading had no effect on leaf area or plant fresh wt, but decreased plant dry wt while increasing plant water content. Nitrogen application increased stem length, and plant fresh and dry wt.
D. J. Makus
Twenty-one day old seedlings of a vegetable amaranth (RCC 241, Amaranthus tricolor) and a grain amaranth (K343, A. hybridus × A. hvpocondriacus) were transplanted on July 28, 1989. Equal applications of NH4N O3 were made on July 28 and August 25 to give total N rates of 0, 60, 120 and 240 kg/ha. Accessions were harvested on Oct. 18 and 14, respectively. Increasing N, induced a quadratic response in plant dry wt, seed wt/plant and seed size fractions in both amaranth types. Seed size fractions as a percent of the total seed, plant height and seed to plant dry weight ratio were not affected by increased N. Seed protein increased linearly whereas seed nitrate increased quadratically with increasing N application. Higher N rates increased residual soil NO3, NR4 and electrolytes and decreased pH. Decreasing soil pH appeared to reduce soil K and Cu but increase Fe and Mn availability. The effect of N rate on seed germination was inconclusive, but the larger seed size was higher in germination. There were differences among species in most responses tested. These data suggest that N applications be tailored to the season growing length required by the respective species/cultivar.
A reflectant particle film material, `Surround', which also has biocide properties, and mycorrhizal root inoculation of tomatoes at transplanting were evaluated for their efficacy in improving tomato plant water status and agronomic performance in a supra-optimal, semi-arid environment. Seven-week-old `Heatmaster' tomato plants (Lycopersicon esculentum Mill.) were transplanted with or without a VAM inoculant (Gomes intaradices, Schenk & Smith) on 19 Feb. 1999 into a Raymondville clay loam soil in Weslaco, Texas (Lat. 26°12'). One-half of the inoculated and one-half of the uninoculated plants were sprayed between 16 Mar. and 1 June with seven applications of `Surround.' The trickle-irrigated plots were 5.6 m2 in size and treatments replicated four times in a RCB design. Recommended cultural practices were followed, but no fungicides were used. Results indicated that mycorrhizal treatment tended to accelerate fruit maturation and that particle film applications delayed fruit development relative to the control treatment. Mycorrhizal-treated plants had the highest yields at the second (of eight) harvest compared to the other treatments. There were no significant differences between treatments in leaf temperature, diffusive resistance, transpiration rate, water potential, and soil profile moisture, except between sampling dates. Fruit mineral nutrients, pigments, dry matter, average weight, total marketable and total season yields were not significantly effected by any treatment. When fruits were sectioned into proximal and distal halves, 10 out of 14 nutrients measured, in addition to dry matter, and total carotenoids were higher in the distal end.
Sulfate, as K2SO4, was applied to silt loam (Leadvale) soils of pH of 5.0 and 7.1 at rates of 0, 6, 18 and 36 kg S/ha. Nitrogen, as NH4NO3, was split applied at 0 and 120 kg/ha. All treatments received 55 and 45 kg/ha of P and K, respectively. Twenty day-old plants of accession RRC 241 were transplanted on 12 July 1990 and harvested 47 days later. Supplemental SO. had no effect on plant ht or yield but increased soil solution SO4 levels at the end of the season. Leaf blade N and S levels were increased at the highest SO4 rate. Higher SO4 rates increased leaf blade chlorophyll (chloro) `a', total chloro and total carotenoid levels. Response of leaf blade total sulfur, sulfate and organic sulfur to supplemental SO4 was linear. Organic to inorganic S ratios were unchanged. Plants grown at pH 5 had lower yields but higher leaf blade K, Al, Fe, Mn, Zn and Cu levels. Plants grown at pH 7 had higher leaf blade P, Ca, Na, and chloro levels. Soil pH did not effect soil solution SO4 levels. N reduced soil pH, and leaf blade P, Ca, Mg, Zn but increased soil electrolytes, leaf blade N, Na, Mn, chloro `a' and `b', and total carotenoids. Leaf blade N was the only leaf consituent from plants grown at both pHs correlated with leaf blade pigments.
D. J. Makus
Four cassava (Manihot esculenta Crantz) accessions were received from the USDA, ARS Plant Introduction Station in Mayaguez, PR on 16 Jan. 1996. The next day the 15- to 20-cm-long cuttings were propagated individually in 1-gal. pots containing Metro Mix No. 4 for 10 weeks before field setting into a transition Hidalgo-McAllen fine sandy loam soil on a USDA, APHIS site near McCook, Texas. Three plant establishment methods, control (no soil amendment), addition of 15 Mt bagasse/ha, or 50 kg cross-linked polyacrylamide/ha into the planting trench were evaluated. The 2 × 1.2 m spacings on 15-cm-high beds provided 4036 plants/ha. Plants received a total of 35.8 cm of water between field planting and harvest (230 days). Mid- and late-season soil moisture (kg/m3) at 38 cm depth only was lowest in soil containing bagasse. Establishment method had little or no effect on plant size, leaf nutrients, leaf pigment concentrations, root dry matter, or root yield. Accessions differed in many of these attributes except root yield, the means of which ranged from 5 to 9 Mt/ha. Only roots survived an air temperature of -5.4 °C on 19 Dec.
Mineral nutrients were determined in green and white `Jersey Giant' asparagus (Asparagus officinalis L.) spears grown in 1991 near Booneville, Ark. Green spears had higher concentrations of tissue N, K, P, S, Na, and Zn; similar levels of Fe, Al, and Cu; and lower levels of NO3 than white spears grown under opaque plastic rowcovers or under sawdust mulch. Levels of Ca, Mg, and Mn were higher in plastic-grown white spears than in those grown in sawdust. The spear tip contained higher concentrations of K, S, and Cu than the butt. Less NO3, Fe, and Al were in the tip than in the butt. Spear distribution gradients for K, Fe, and Cu were linear, whereas S and NO3 gradients were both linear and quadratic. Nitrogen, P, Ca, Mg, Zn, Al, and Mn levels were influenced by spear production method and spear segment.
D. J. Makus
On 3 Aug. 1993, 20-day-old `Hinn Choy' plants (Amaranthus tricolor L.) were-planted on 15 × 15 cm spacings in 4-row beds at 1.3 m row spacings in a Leadvale silt loam soil. Nitrogen sources of NH4, NO3 and NH4 NO3 were used at rates of 0, 100 and 200 kg/ha, and were split-applied at and 1 week after transplanting. All treatments received both supplemental K and P at the rate of 90 kg/ha at planting. Plants were harvested 31 days after transplanting. Plants given the NH, source were taller, and were higher in yield, leaf chlorophyll, total carotenoids and Mn (dry wt basis) than were plants given other N-sources. NO3-N fertilizer increased leaf Fe and Cu, and residual soil K and NO3, but reduced Mn levels. Leaf blade Ca was highest when NH4NO3 fertilizer was used. Increasing N-rates decreased both soil pH linearly and leaf blade Ca but linearly increased soil EC, NO3, and S and leaf blade N, K, S, P, NO3, Fe, chlorophyll and carotenoids.