Progress 12/23/97 to 09/30/03
Outputs
A preliminary multi-year field trial examined several cash and non-cash (cover) crops for their ability to remediate compacted soils. Initial soil penetrometer resistance was 2.9 and 1.4 MPa (15 cm depth) on compacted and uncompacted plots, respectively. Sudangrass significantly reduced penetrometer resistance (to 2.2 MPa) in compacted plots within the first year, while Hubam sweet clover, bean and corn crops did not. Among plots that were initially compacted, plots that were deep tilled the first year followed by rotation sequences that included sudangrass, sweet corn, and perennial ryegrass had the best soil quality (low soil penetrometer resistance, high water infiltration rate and organic matter content) and highest snap bean yield in the third year of rotation. Subsequent replicated field experiments tested the hypothesis that mowing sudangrass enhanced root growth, and found that mowing to a 6 inch height when plants reached the 2 to 4 ft. height stage had no
significant effect on root depth or root number counts (monitored with minirhizotron observation tubes) compared to unmowed controls, but did reduce final root and shoot biomass by about 30 and 40 percent, respectively. Nitrogen (N) fertilization (90 lbs N per acre) increased biomass production by 30 to 40 percent, but root:shoot ratio and minirhizotron root counts at the 10 and 50 cm depth were higher in unfertilized plots. Averaging across management treatments, the sorghum-sudan hybrid (Sorghum bicolor var. sudanense, cv. Sudex) produced more total biomass, had a higher root:shoot ratio, and higher minirhizotron root counts than the sudangrass hybrid (S. bicolor var. bicolor, cv. Trudan-8). In a separate greenhouse experiment we found that a compacted soil layer at the 10 to 20 cm depth reduced Rhizobium root nodulation by 95 percent compared to uncompacted controls in a legume cover crop (lana vetch, Vicia dasycarpa), and cash crop (snap beans). Total biomass production of bean
plants (measured at 40 days after planting) was reduced by 70 percent in compacted treatments, while total biomass production of lana vetch was not significantly affected. Another field experiment tested the hypothesis that sweet corn root growth could be enhanced by inoculation of seed with the commercially available rhizosphere fungus, Trichoderma harzianum (strain T22). Results of 2 years of replicated field experiments found that T22 inoculation significantly increased early and mid-season sweet corn (var. Candy Corner) root biomass by 10 to 20 percent, and total biomass by 20 to 30 percent. However, T22 inoculation did not significantly increase the number or fresh weight of marketable ears. In another field study, we tested the hypothesis that rising atmospheric CO2 will increase the root-shoot ratio of cover crops. A replicated field study with fall-seeded grain rye grown at ambient (350 ppm) and elevated (700 ppm) CO2 concentrations in semi-open polyethylene chambers found no
significant CO2 effect on total rye biomass, but a higher proportion of total biomass allocated to roots and a higher C:N ratio of crop residue at 700 compared to 350 ppm CO2.
Impacts
These results have been integrated into a newly initiated NYS soil health education program. Commercial plantings of sudangrass have increased in the region, based in part on our data indicating beneficial effects on soil quality. Growers have better information regarding varietal, nitrogen, and mowing effects on sudangrass root growth and organic matter contribution. Growers are more aware of soil compaction effects on symbiotic N-fixation in legume crops. Our sweet corn study confirmed root (and shoot) biomass of sweet corn were significantly increased by inoculation with the commercially available root fungus, Trichoderma harzianum, but sweet corn ear yields were not affected. Results of the grain rye and CO2 field study indicate that rising atmospheric CO2 will increase the root:shoot biomass and C:N ratios of this cover crop, with implications for organic matter distribution and decomposition rate.
Publications
- WOLFE, D.W., ABAWI, G.S., THIES, J., DRINKWATER, L. 2003. Biological indicators of soil health. Dept. of Horticulture Report. Cornell University. Ithaca, NY.
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Progress 01/01/02 to 12/31/02
Outputs
Multi-year, replicated field and greenhouse experiments evaluated management and variety effects on above- and below-ground growth of sudangrass-a cover crop recommended for high organic matter contribution and root growth into compacted soils. Mowing to a 6-in. height when plants reached the 2 - 4 ft. height stage had no significant effect on root depth or root number counts monitored with minirhizotron observation tubes, but did reduce final root and shoot biomass by about 30 and 40 percent, respectively, with significantly less seasonal biomass production when mowed at 2 ft. compared to 4 ft.. Nitrogen (N) fertilization (90 lbs N per acre) increased biomass production by 30 - 40 percent, but root:shoot ratio and minirhizotron root counts at the 10 and 50 cm depth were higher in unfertilized plots. Averaging across management treatments, the sorghum-sudan hybrid (Sorghum bicolor var. sudanense, cv. Sudex) produced more total biomass, had a higher root:shoot ratio,
and higher minirhizotron root counts than the sudangrass hybrid (S. bicolor var. bicolor, cv. Trudan-8). In a separate greenhouse study, it was found that Rhizobium root nodulation within a compacted soil layer at the 10 - 20 cm depth was reduced by 95 percent compared to uncompacted controls in both the legume cover crop, lana vetch (Vicia dasycarpa), and legume cash crop, snap beans (Phaseolus vulgaris, cv. Bush Blue Lake 274). Total biomass production of bean plants (measured at 40 days after planting) was reduced by 70 percent in compacted treatments, while total biomass production of lana vetch was not significantly affected. Prior research has suggested that sweet corn may be a beneficial rotation crop because of the ability of its roots to penetrate shallow compacted layers. Observational reports have suggested that sweet corn root growth, as well as nitrogen use efficiency and yield, may be enhanced by inoculation of seed with the commercially available rhizosphere fungus,
Trichoderma harzianum (strain T22). Results of 2 years of replicated field experiments found that T22 inoculation significantly increased early and mid-season sweet corn (var. Candy Corner) root biomass by 10 - 20 percent, and total biomass by 20 - 30 percent. However, T22 inoculation did not significantly increase the number or fresh weight of marketable ears. Tissue N analyses for N use efficiency calculations are in progress. A replicated field study with fall-seeded grain rye (Secale cereale) grown at ambient (350 ppm) and elevated (700 ppm) CO2 concentrations in semi-open polyethylene chambers found no significant CO2 effect on total rye biomass, but a higher proportion of total biomass allocated to roots and a higher C:N ratio of crop residue at 700 compared to 350 ppm CO2.
Impacts
Growers in the region have new information regarding varietal, nitrogen, and mowing effects on sudangrass root growth and organic matter contribution. We have now documented that mowing reduces seasonal biomass production compared to uncut controls, but delaying mowing until plants reach a 4-ft height has less negative impact than mowing at the 2-ft. stage. While mowing reduced root biomass in all cases in our experiments, it did not have a significant effect on root depth or root counts measured with minirhizotron observation tubes. Results of the soil compaction study indicate that root nodulation by symbiotic N-fixing bacteria is severely reduced within compacted layers regardless of legume species, but plant growth response to compaction is species-dependent. Our sweet corn study did not confirm a significant effect on marketable ear yield from inoculation with the commercially available root fungus, Trichoderma harzianum, but both root and shoot biomass were
significantly increased. Results of the grain rye - CO2 field study indicate that rising atmospheric CO2 will increase the root:shoot biomass and C:N ratios of this cover crop, with implications for organic matter distribution and decomposition rate.
Publications
- Wolfe, D.W. 2002. Summary report of the soil health grower survey. Dept. of Horticulture Report. Cornell University. Ithaca, NY.
- Stivers, L.J., Brainard, D.C., Abawi, G.S., Wolfe, D.W. 1999. Use of Cover Crops in Northeast Vegetable Production. Cornell Cooperative Extension Bulletin 244, Ithaca, NY.
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Progress 01/01/01 to 12/31/01
Outputs
Prior studies have indicated that sweet corn can be a particularly beneficial vegetable crop to include in rotation on compacted and poor quality soils because of the ability of its roots to penetrate shallow compacted layers, and its contribution to organic matter and overall soil quality. Preliminary reports have suggested that these beneficial effects might be enhanced by inoculation of sweet corn seed with the rhizosphere fungus, Trichoderma harzianum, which can stimulate root growth, improve crop nitrogen use efficiency, and increase biomass production and yields. A field study was conducted to test these claims. Sweet corn (var. Candy Corner) was planted with and without seed inoculation (2.8 g per 454 g seed) with Trichoderma harzianum (strain T22) on a sandy loam soil, with or without supplemental nitrogen (N) fertilizer (ammonium nitrate) at a rate of 230 kg N/ha (in split applications), in a randomized complete block design with 4 replications. Presumably
due to residual soil N, high rates of N mineralization, and low rainfall in the early spring, there was little evidence of N deficiency in the unfertilized plots. In these unfertilized, moderate N, plots, there was no significant response to T22 for any of the variables measured. In contrast, at high N (fertilized plots), T22-inoculated plants had 44, 27, and 21 percent higher ear, root, and total biomass at final harvest, respectively, compared to non-inoculated plants. Plant N uptake efficiency (plant N/soil N) was also significantly increased by T22 in fertilized plots, due in part to larger plants and also to a 25 percent increase in overall N concentration of plant tissues. Plant N utilization efficiency (ear dry wt/plant N) and N harvest index (ear N/total plant N) were not significantly affected by T22 inoculation in fertilized or unfertilized plots, however. In a separate field study, grain rye (Secale cereale) was seeded in the fall into 3 m x 3 m semi-open polyethylene
canopy chambers maintained at either ambient (350 ppm) or elevated (700 ppm) carbon dioxide (CO2). The following spring, 0.5 square meter from each of the 3 replications of each CO2 treatment were harvested. CO2 had no significant effect on total rye biomass, but the proportion of total biomass allocated to roots, and the C:N ratio of rye crop residue, were significantly higher at elevated compared to ambient CO2. Analysis of soil samples for N availability and C and N in microbial biomass is in progress.
Impacts
Results of the sweet corn study provide information useful in determining the potential benefits of including sweet corn in rotation for improving soil quality and nitrogen use efficiency, and whether seed innoculation with the rhizosphere fungus, Trichoderma harzianum, can enhance these beneficial effects. Results of the grain rye - CO2 study provide information useful in predicting the possible effect of rising atmospheric CO2 on C and N cycling and soil N availability to crops.
Publications
- No publications reported this period
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Progress 01/01/00 to 12/31/00
Outputs
The effect of soil compaction on nodulation of legume roots by nitrogen-fixing bacteria was evaluated. The legume species Phaseolus vulgaris (snap beans, var. Bush Blue Lake 274) and Vicia dasycarpa (lana vetch) were seeded into 6-liter pots filled with Eel silt loam soil. Prior to seeding, half the pots were compacted at the 10-20 cm depth (CP) and the others were left uncompacted (UC) throughout the entire 0-20 cm soil depth. All of the pots were innoculated with a commercial Rhizobium mixture prior to seeding, but did not receive any supplemental fertilizer. Plants were grown in the greenhouse and watered such that soil moisture levels were maintained within the .01 - .03 MPa range at the 10 cm depth, based on tensiometers placed in 3 of the 10 replications (pots) of each species/compaction treatment. Pots were thinned to 1 bean plant and 9 - 10 vetch plants per pot after emergence. Plants were destructively harvested at the flowering stage (36-40 days after
planting), and soil and roots from the upper and lower 10 cm of the soil profile were separately sifted to retrieve root nodules. Washed root nodules and above-ground plant parts were dried at 75 C for 48 hours and weighed. Beans were in general more sensitive to compaction than the vetch, but both species showed about a 95 percent reduction in nodulation at the 10-20 cm depth (compacted layer) in CP compared to UC pots. Nodule dry weights within the 0-10 cm (uncompacted layer) of CP pots was also reduced (by 50 percent) compared to UC pots for bean, but there was no significant difference between CP and UC pots in nodule dry weights at 0-10 cm for lana vetch. Bean total biomass was 70 percent reduced in CP compared to UC pots, while total biomass production of lana vetch was not significantly affected by compaction treatment. In a separate field study, the effect of soil nitrogen availability on root distribution of sudangrass (Sorghum bicolor x S. bicolor, var. sudanense) was
evaluated. Plants were grown on an Eel loam soil and either fertilized with a preplant application of 700 kg per hectare of 13-13-13 N-P-K fertilizer or not fertilized. There were 3 replications (plot dimensions of 5 x 10 meters) of each treatment. Plants were mowed to a height of 15 cm when they had reached about the 120 cm height stage. Total biomass was substantially reduced in unfertilized compared to fertilized plots, but root:shoot ratio was higher in unfertilized plots, and analysis of root count video image data collected from clear polyethylene minirhizotron observation tubes installed in each plot revealed a higher root count in the upper 30 cm of soil in unfertilized compared to fertilized plots, and no significant fertilizer effect on root counts lower in the soil profile (to an 80 cm depth). Follow-up experiments are planned to examine in more detail fertility effects on root distribution, and to develop fertilizer recommendations for sudangrass to optimize both biomass
production and root penetration into compacted soil layers.
Impacts
Our results suggest that nodulation by symbiotic N-fixing bacteria (Rhizobium) is severely reduced in compacted soil layers regardless of legume genotype, but overall plant growth response to compaction varies widely, depending on the depth of the compacted layer and legume genotype. Root growth in the upper soil profile and root:shoot ratio of sudangrass is stimulated at low compared to high soil N fertility. With further corroboration, this information will be useful in developing management recommendations for use of sudangrass to remediate compacted soils
Publications
- No publications reported this period
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Progress 01/01/99 to 12/31/99
Outputs
Field and greenhouse studies were conducted to examine in detail the effects of management practices and variety on above- and below-ground growth of sudangrass. Prior research has indicated that sudangrass is a particularly effective rotation cover crop in the Northeast for ncreasing soil organic matter and for breaking up shallow compacted soil layers. In the field experiment there were 2 varieties: S. bicolor var. bicolor hybrid and a sorghum-sudan (S. bicolor x S. bicolor var. sudanense) hybrid; and 3 mowing treatments: not mowed vs. mowed (to a 6-inch height) when plants reached 2 or 4 ft. high. The dimensions of each plot were 16 ft x 30 ft. Minirhizotron clear polyethylene observation tubes were installed for video imaging of root growth to a depth of 1 m. In mowed treatments, clippings were collected from a 1 m2 area within each plot, dried, weighed, and clippings were returned to the field. At final harvest, 1m2 of each plot was destructively harvested and
plant material dried for determination of above-ground biomass. Analysis of the minirhizotron video image data revealed that in the upper soil profile (0 - 30 cm depth), the sorghum-sudan hybrid had significantly more roots than the sudan hybrid. Both varieties had significant root penetration to the 80 cm depth. There was some uggestions that in the lower portion of the profile (50 - 70 cm depth), the sudan hybrid had a higher root density than the sorghum-sudan hybrid, but this was not statistically significant. Surprisingly, mowing did not have a significant effect on root counts for either variety, even though above-ground biomass was reduced substantially by mowing, and we assume total root biomass (not measured) was also reduced. The above-ground biomass was reduced by 44 percent and 38 percent when mowed at the 2 ft and 4 ft stage, respectively for the sorghum-sudan hybrid. For the sudan hybrid, above-ground biomass was reduced by 53 percent and 35 percent when mowed at the 2
ft and 4 ft height, respectively. Conclusions from the field study are that both sudangrass varieties examined had substantial root development to a depth of 80 cm, and mowing did not significantly reduce the depth of root penetration. The sorghum-sudan hybrid had a higher proportion of roots in the upper part of the profile, whereas the sudangrass hybrid had a more uniform root distribution with depth. In greenhouse experiments the same two varieties were grown in 2-gallon pots of 9 inch diameter in a loam soil at commercial densities (14 plants per pot). The two varieties produced similar total biomass (within the 40-day duration of the greenhouse experiments), but the sorghum-sudan hybrid had a significantly higher root biomass and a higher root:shoot ratio. Clipping plants at the 2 ft. height reduced total biomass, but did not significantly affect root:shoot ratio of either variety.
Impacts
(N/A)
Publications
- No publications reported this period
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Progress 01/01/98 to 12/31/98
Outputs
Prior research conducted in New York indicated that a sudangrass hybrid (Sorghum bicolor var. sudanense) produced the most above-ground biomass of several cover crops evaluated, and also was the most effective at breaking up shallow compacted soil layers, and improving other soil quality parameters. A field study with 3 replications was conducted on an Eel loam soil in 1998 to begin to develop sudangrass variety and crop management recommendations for growers. There were 2 varieties: S. bicolor var. bicolor hybrid and a sorghum-sudan (S. bicolor x S. bicolor var. sudanense) hybrid; 2 fertilizer treatments: no fertilization vs. preplant broadcast application of 700 lbs. per acre 13-13-13 N-P-K fertilizer; and 3 mowing treatments: not mowed vs. mowed (to a 6-inch height) when plants reached 2 or 4 ft. high. The dimensions of each plot was 16 ft x 30 ft.. Minirhizotron clear polyethylene observation tubes were installed for video imaging of root growth to a depth of 1 m
(in non-fertilized plots only). In mowed treatments, clippings were collected from a 1 m2 area within each plot, dried, weighed, and clippings were returned to the field. At final harvest, 1m2 of each plot was destructively harvested and plant material dried for determination of above-ground biomass. In terms of total biomass production (which included clippings of mowed treatments), not mowed treatments (which grew to about 8 ft by the end of the season) had highest yields (1229 g/m2), followed by those mowed at the 4 and 2 ft height, with yields of 831 and 743 g/m2, respectively. Fertilized plots had an average yield of 1084 g/m2 compared to 784 g/m2 for unfertilized. Averaging across mowing and fertilizer treatments, the sorghum-sudan hybrid had a significantly higher yield (959 g/m2) than the sudangrass hybrid (910 g/m2). Root video image data are still being analyzed, but initial analyses suggest higher total root counts for the sorghum-sudan hybrid, but no obvious effect from
mowing. However, visual observations suggest a profusion of new roots stimulated by tillering in mowed treatments, even though total root biomass may be reduced. In supplemental greenhouse experiments, mowing reduced above and below-ground biomass, although plants were not grown to maturity. In the greenhouse experiments both shoot and root growth were slightly higher in the sorghum-sudan hybrid compared to the sudan hybrid, as was observed in the field. This first year's results suggest that the sorghum-sudan hybrid is superior to the sudan hybrid, mowing at a later rather than early stage is preferable, and significant increases in total biomass production can be obtained by addition of preplant N-P-K fertilizer.
Impacts
(N/A)
Publications
- Stivers, L.J., Brainard, D.C., Abawi, G.S., Wolfe, D.W. 1999. Use of Cover Crops in Northeast Vegetable Production. Cornell Cooperative Extension Bulletin, Ithaca, NY.
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