Tomato (Solanum lycopersicum) fruit quality and yield are highly dependent on adequate uptake of nutrients. Potassium, magnesium and calcium are essential elements that influence fruit quality traits such as colour, uniformity of ripening, hollow fruit, fruit shape, firmness and acidity. Sodium is not an essential element for tomato and can detrimentally compete with the absorption of potassium and calcium. Daily intakes of potassium, magnesium and calcium in human diets are typically below healthful levels, while sodium intake is often excessive. The objective of this study was to compare 52 diverse commercially important varieties of tomato for concentrations of potassium, magnesium, calcium and sodium in fruits. The tomatoes were produced in replicated plots in Geneva, NY in 2010 and 2011. Multiple fruits per plot were harvested vine-ripe, homogenized and assayed for cations. Analysis of variance showed significant differences among the 52 varieties for all four traits, i.e. cation concentrations (df = 51, P < 0.0001–0.0034) and no significant differences between years for any trait (df = 1, P = 0.3432–0.6770). Factor analysis showed a strong interrelationship between potassium and magnesium that was independent of calcium and sodium. Potassium and magnesium were highly significantly correlated with each other (r = 0.64, P < 0.0001). No other correlations between pairs of traits were observed. Results supported a genetic basis for potassium, magnesium, calcium and sodium concentrations that was consistent across environments (i.e. years). Results can contribute to the development of cultivars with favourable cation profiles in terms of human health and fruit quality.

This study evaluated the profitability of several cropping systems during a 10-year period of an experiment comparing rotations and levels of purchased inputs. Continuous corn or sorghum, corn/wheat-soybean (2-year), and corn/wheat-soybean/corn/clover hay (4-year) were managed with recommended fertilizer and pesticide rates and no-till planting (C) or with N from legumes, conventional tillage, and cultivation for weed control (L). Medium input management (M: medium rate of N and banded herbicides) was included during years 5 through 10. Generally, corn was the least profitable crop, regardless of input level or type of rotation. Rotating crops improved profit more than did adding inputs to continuous corn. With L, average annual profit was: continuous corn, -$64/ha; 2-year rotation, $135/ha; and 4-year rotation, $158/ha. With C, the 2-year rotation increased profit to $165/ha from -$119/ha with continuous corn. The increased profit with rotations was due to greater profits from wheat, soybean, and hay offsetting low or negative profit from corn. Sorghum (grown only in monoculture) was more profitable with L ($34/ha) than with C (-$20/ha). During the 6 years when all input levels were compared, the order of average profit was M>L>C with continuous corn. Generally, profit was not increased by M compared with L in the 2-and 4-year rotations. With L, the cost of weed control was 20% of that for C with corn and 44% with soybean. Cost of N from fertilizer was $0.66/kg, but cost of N from crimson clover (seed and planting costs) averaged $0.92/kg when clover was drilled, $1.27/kg when aerially seeded, and $0.16/kg when naturally reseeded.

We monitored emergence of morning-glory, pigweed, and prickly sida from seeded populations in no-till plots with no debris (reference plots) or with crimson clover, subterranean clover, rye, or wheat debris. Cover crops were either desiccated by glyphosate or mowed and tilled into the soil. Debris levels, soil temperature, moisture, pH, nitrate, total phenolic acid and compaction were monitored during May to August in both 1992 and 1993. Seedling emergence for all three weed species ranged from <1 to 16% of seeds sown. Surface debris treatments delayed weed seedling emergence compared with the reference plots. Rye and wheat debris consistently suppressed weed emergence; in contrast, the effects of clover debris on weed emergence ranged from suppression to stimulation. Gfyphosate application resulted in a longer delay and greater suppression of seedling emergence in May than in April. In 1993, plots in which living biomass was tilled into the soil were also included and monitored. Weed seedling emergence was stimulated when living biomass was incorporated into the soil. Covariate, correlation and principle component analyses did not identify significant relationships between weed seedling emergence and soil physical and chemical characteristics (e.g., total phenolic acid, nitrate, moisture, temperature). We hypothesize that the observed initial delay of the weed seedling emergence for all three species was likely due to low initial soil moisture. The subsequent rapid recovery of seedling emergence of morning-glory and pigweed but notprickfy sida in the clover compared with the small grain debris plots was likely due to variation in soil allelopathic agents or nitrate-N levels. The stimulation of weed seedling emergence when living biomass was incorporated into the soil was likely caused by an increase in “safe” germination sites coupled with the absence of a zone of inhibition resulting from tillage.

Interest in developing more sustainable cropping systems has led to renewed interest in legumes as N sources for crops. We conducted a 2-year study to compare the effects of green manure, green manure plus fertilizer, and fertilizer on wheat yield and N leaching potential. In 1991–92, wheat following corn and receiving 0, 45, or 90 kg N/ha was compared with wheat planted after plowing the autumn regrowth of red clover/johnsongrass hay (supplemented with alfalfa) that supplied 107 kg total N/ha. In 1992–93, wheat following corn and receiving 90 kg N/ha was compared with wheat following hay regrowth that either received fertilizer N at 45 kg/ha or 90 kg N/ha or was supplemented with alfalfa (total of 123 kg N/ha). Yield with only green manure averaged 65% of yield with 90 kg N/ha. Yields with green manure plus 45 or 90 kg N/ha were not different from yield with 90 kg N only. The first year, soil to a depth of 30 cm declined from as high as 40 kg/ha in the fall to less than 10 kg/ha as wheat growth increased in the spring. In contrast, concentration averaged 20 kg/ha throughout the growing season. Trends in soil inorganic N were similar the second year. Profile nitrate distribution indicated a greater potential for N leaching with fertilizer than with green manure. Soil from the site was used in a laboratory incubation study to determine the rate of N mineralization from white clover at 10°C. An average of 80% of the clover N was recovered as soil inorganic N; however, in the field study, recovery (soil inorganic N in the 0 to 30-cm zone + Nin above-ground wheat biomass) was only 21%. Supplementing green manures with spring applications of fertilizer N could decrease the leaching loss without decreasing wheat yield.

In a previous study of reduced chemical cropping systems (N from legumes; chisel plow and disk tillage; cultivation for weed control) in the southeastern U.S., corn and wheat yields were less than half those obtained with recommended practices. The following practices were studied as possible ways to improve yields in the reduced chemical systems: 1) conventional tillage (chisel plowing and disking), inorganic Nat 70 or 140 kg/ha, and either cultivation or herbicides; 2) early versus late plow-down of clover green manures; 3) supplemental inorganic N fertilizer on corn and wheat in rotations relying on clover green manures for N; and 4) nicosulfuron herbicide banded on corn.

Yield of soybean in the rotations was not affected by any of these practices. With herbicides and fertilizer N at 140 kg/ha, continuous corn yields with no-till and conventional tillage were equal in 1990 and 1992, but no-till yield was 30% higher in 1991. When cultivation was used for weed control in the conventional tillage treatment, corn yield was similar to that of no-till with herbicide in the one year when rain was plentiful (yield 6000 kg/ha). However, in 2 of 4 dry years, yields (<2600 kg/ha) were higher with no-till. Clover biomass consistently increased by between 700 and 3500 kg/ha when plow-down was delayed from mid-April to early or mid-May (13 to 26 days). However, biomass N content increased significantly (by between 35 and 90 kg/ha) in only 2 of 5 years. Corn yields were affected in only 2 of 12 possible comparisons. In these cases, delayed clover plow-down reduced yield by about 50%. Supplementing corn with 45 kg N/ha and banding nicosulfuron increased yields, but only to between 62 and 84% of yields with recommended practices. Supplementing wheat with 45 kg N/ha increased yields by half, but only to between 40 and 60% of the yields with 90 kg N/ha.

Interest in reducing purchased chemical inputs to reduce production costs and avoid possible environmental damage prompted this 7-year study. Two management systems, current management practices (CMP) and reduced chemical inputs (RCI), were evaluated for four crop sequences from 1985 through 1992: continuous grain sorghum; continuous corn; a 2-year rotation of corn and double-cropped winter wheat and soybean; and a 4-year rotation of corn, winter wheat/soybean, corn, and red clover hay (changed in 1989 to a 3-year rotation of corn, red clover hay, and wheat/soybean). No-till planting and recommended rates of fertilizer and pesticides were used in the CMP system. In the RCI system, N was supplied by a crimson clover green manure crop or the red clover in the rotation. Weed control was by chisel plowing, disking, and cultivation.

Crimson clover top growth accumulated from 70 to 180 kgN/ha, red clover from 77 to 130 kg N/ha. Rotating crops increased corn yield with CMP but not with RCI. lndry years, corn yields were low (less than 3000 kg/ha), corn did not respond to fertilizer N, and yields generally were higher with CMP than with RCI. With adequate rain, yield of all RCI treatments were the same as yield in CMP continuous corn receiving no fertilizer N. Johnsongrass competition was the main reason for low yields in the RCI treatments. Soybean yields were higher with CMP in 4 years and higher with RCI one year. Wheat and grain sorghum yields were higher with CMP than with RCI. A dramatic decline in johnsongrass in sorghum was noted in 1989, and several plots remained relatively free of johnsongrass through 1992.

Management decisions made during the experiment included the degree of input reduction in RCI; whether to either end or modify unproductive treatments; whether to use newly available varieties and pesticides; whether to suspend the experiment to eliminate johnsongrass; and how to add new treatments while retaining the original treatments.

Soils from adjoining farms, one managed organically and the other managed conventionally, were used in a greenhouse study to compare soil P status and the efficiency of concentrated superphosphate (CSP) and North Carolina rock phosphate (RP). Soil and plant parameters were measured as indicators of levels of soil P forms and availability of soil P to soybeans (Glycine max L.). Management did not affect dry matter yield of soybean plants. Conventional management resulted in higher P concentration in the plant and higher P uptake when CSP was the P source. However, when RP was the source, management effect was not significant. RP was only 15% as effective as CSP in increasing yield. When no P was applied, organic management resulted in greater total soil P, organic P, and Ca phosphate (CaP); conventional management resulted in greater Al and Fe phosphate (AlFeP) and occluded AlFeP (OcP). Addition of CSP increased AlFeP and OcP. Addition of RP increased CaP. CSP was more effective than RP in increasing extractable soil P. Multiple regression analysis showed that extractable P was related to AlFeP when CSP was the P source and to CaP when RP was the source. Yield was related to extractable P when CSP was the P source but when RP was the source, no significant regression models were found for yield.