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An experiment was established to determine the effect of different winter cover crops residues on yields of no-till pumpkins, yellow summer squash, and sweet corn. Residue treatments of fallow, triticale, crimson clover, little barley, and crimson clover + little barley were fall established and killed before spring no-till planting in 1998 and 1999. All summer vegetables received recommended fertilizer rates and labeled pesticides. Spring cover crop growth and biomass measurements ranged from 1873 to 6362 kg/ha. No-till sweet corn yields among the various cover residue treatments were greater where crimson clover and crimson clover + little barley (mixture) were used as residue in 1999, but not significantly different in 1998. No-till pumpkins showed the beneficial affect cover crop residue had on vegetable yields when dry conditions exist. Triticale and crimson clover + little barley (mixture) residues reduced soil water evaporation and produced more numbers of fruit per hectare (5049 and 5214, respectively) and greater weights of fruit (20.8 and 20.9 Mg/ha) than the other residue treatments (3725 to 4221 fruit/ha and 11.8 to 16.1 Mg/ha, respectively). No-till summer squash harvest showed steady increases in yield through time by all treatments with crimson clover residue treatment with the greatest squash yields and triticale and little barley residue treatments with the lowest squash yields. We found that sweet corn and squash yields were greater where legume cover residues were used compared to grass cover residues, whereas, pumpkin yields were higher where the greatest quantity of mulch was present at harvest (grass residues).
Current goals for space exploration are predicated upon long-term manned space flights and colonization of planetary habitats. Long periods in space without payloads of necessary items from Earth require the development of a self-sustaining ecosystem that will allow astronauts to grow their own food and efficiently recycle the waste products. Crops suggested for growth in space include wheat, rice, carrots, soybean, mushrooms, etc. Optimal and rapid biodegradation of lignin and other cellulosic material of crop residues by candidate edible white rot fungal strains is paramount in the use of these organisms to achieve effective biomass recycling in an advanced life support system (ALS). The incorporation of organic N into the substrate and pairing crop residues may enhance growth and fruiting of the edible fungi, thus increasing the rate of biodegradation of the substrates and biomass recycling. We investigated the mycelial growth of two strains of Pleurotusostreatus (`Grey Dover' and `Blue Dolphin') on processed single vegetative residues of soybean, cowpea, tomato, sweetpotato, or their 1:1 combination with wheat or rice straw. Growth and fruiting of the two strains including another strain (`Pohu') on rice straw mixed with solid thermophilic aerobic reactor (STAR) effluent for degradation and recycling were also studied. Mycelial growth and fruiting in `Grey Dover' and `Blue Dolphin' were significantly repressed on sweetpotato and basil; however, growth of the two strains was improved when sweetpotato and basil substrates were paired with rice or wheat straw. Fruiting was prolific in paired combinations of soybean with wheat or rice straw. High concentration of STAR residue enhanced mycelial growth; however, a relatively lower concentration was required for abundant fruiting.
Fall-planted cover crops killed in spring is practiced in strawberry cultivation in different regions of the North America. These systems have shown significant weed suppression and conservation of soil without significant yield reduction in strawberry. During the establishment season, this study was initiated to assess weed suppression with cover crops (`Wheeler' rye and `Micah' and `Steptoe' barley) along with perlite, an artificial plant medium. Strawberry (`Selva' and `Totem') plant growth and weed biomass were measured during 1995-96 season. Small-seeded summer annual weeds were suppressed in cover crop treatments compared to control treatment. `Micah' barley in growth phase suppressed more than 81% of the total weed biomass compared to control plots with no cover crop in early spring. However, in early summer, cover crop residues failed to suppress different types of weeds 60 days after killing of cereal with herbicide (2% glyphosate). Distinct differences in strawberry plant growth were evident between the cover crop treatments and non-cover crop treatments including `Micah' applied on surface. Strawberry growth was doubled during 10 July to 15 Aug. in both cultivars. `Micah' barley applied on surface produced better growth in both strawberry varieties than the growth in other treatments. `Micah' barley applied on soil surface produced 50% more strawberry shoot biomass may indicate the root competition between cover crops and strawberry.
A U.S. Environmental Protection Agency (EPA) voluntary program encourages the registration of pesticides that represent reduced risk to human health and the environment. A “reduced risk” designation for a pesticide depends on how its use will affect human health and the environment, pesticide resistance, and pesticide management. Prohexadione-Ca is a bioregulator being developed by BASF Corporation to control vegetative growth in apples with the effect of improving fruit production. BASF will petition the EPA to register prohexadione-Ca as a reduced risk pesticide in 1997 based on the following properties associated with its use: Prohexadione-Ca exhibits a very low mammalian toxicity and a low propensity for crop residues. Prohexadione-Ca rapidly dissipates in soil as a result of microbial metabolism and causes no detrimental ecological effects. There is no other hazard associated with the compound and no health risk for user or consumer is indicated. The use of prohexadione-Ca reduces the incidence of fireblight (and helps control this disease). The use of prohexadione-Ca reduces tree row spray volumes of other pesticides up to 25%. With these beneficial characteristics, prohexadione-Ca will fit exceptionally well into an Integrated Pest Management (IPM) program, providing another “reduced risk” justification for the registration of prohexadione-Ca. The current situation of accepting prohexadione-Ca as a reduced risk pesticide and its registration status will be discussed.
Mustard (Brassica spp.) cover crop residue has been reported to have significant `biofumigant' action when incorporated into soil, potentially providing disease suppression and yield improvement for the succeeding crop. The effects of growing over-winter mustard cover crops preceding processing tomato (Lycopersicon escultentum Mill.) production were investigated in six field trials in the Sacramento Valley of California from 2002–04. A selection of mustard cover crops were compared to a legume cover crop mix, a fallow-bed treatment (the current grower practice in the region), and in two of the six trials, fumigation treatments using metam sodium. Mustard cover crops removed 115 to 350 kg·ha–1 N from the soil profile, reducing NO3-N leaching potential. Soil populations of Verticillium dahliae Kleb. and Fusarium spp. were unaffected by the cover crops, and there was no evidence of soilborne disease suppression on subsequent tomato crops. Mustard cover crops increased tomato yield in one field, and reduced yield in two fields. In one of two fields, metam sodium fumigation significantly increased tomato yield. We conclude that, while environmental benefits may be achieved, mustard cover cropping offers no immediate agronomic benefit for processing tomato production.
Mustard cover crop residue has been reported to have a “biofumigant” action when incorporated into the soil, potentially providing significant disease suppression and yield improvement for the succeeding crop. Such activity could be particularly useful in processing tomato rotations, where consecutive cropping invariably results in yield decline. Agronomic and environmental effects of growing over-winter mustard cover crops preceding tomato production were investigated in three field trials between 2002 and 2004. Two mustard cover crops [`Pacific Gold', a brown mustard (Brassica juncea), and `Caliente', a blend of brown and white mustard (Sinapis alba)] were compared to a legume cover crop mix, a fallow bed treatment (the standard grower practice in this region), and, in two of the three trials, a fumigation treatment using metam sodium. No suppression of soil populations of Verticillium dahliae or Fusarium spp. was observed with the mustard cover crops, nor was there any visual evidence of disease suppression on subsequent tomato crops. In these fields, the mustard either had no effect, or reduced tomato yield, when compared to the fallow treatment. At one of two sites, metam sodium fumigation significantly increased tomato yield. The presence of a cover crop, whether mustard or legume, reduced winter runoff by an average of 50% over two years of trials. No benefit of mustard cover cropping beyond this reduction in winter runoff was observed.
Field research was conducted in Deerfield, Mass. to study the effects of leguminous cover crops on sweet corn yield. Oat was planted alone and in combination with four leguminous cover crops August 8, 1990. Cover crop residue was disked once and sweet corn seeded April 23, 1991. Each cover crop combination had three rates of nitrogen added in two applications. Sweet corn seeded into stands of hairy vetch (Vicia villosa) yielded the highest of the cover crop combinations. All leguminous cover crop treatments yielded higher than oat alone or no cover crop when no synthetic nitrogen was added. Cover crop combinations were seeded again in the same field plots August 12, 1991. Oat biomass in November was greater where there had been leguminous cover crops or high rates of synthetic nitrogen. Legume growth was retarded in the plots that had previously received high nitrogen. It is thought that legume growth was reduced in the high nitrogen treatments due to increased oat growth and higher soil nitrogen levels which could inhibit root nodulation.
Laboratory experiments were conducted to study the effect of aqueous extracts of hairy vetch (Vicia villosa Roth) and cowpea (Vigna unguiculata (L.) Walp) cover crops on germination and radicle elongation in seven vegetable and six weed species. Lyophilized aqueous extracts of the cover crops were dissolved in reverse osmosis (RO) water to produce seven concentrations: 0.00, 0.25, 0.50, 1.00, 2.00, 4.00, and 8.00 g·L–1. Each treatment had 4 replications and the full experiment was repeated. Experiment 1 (E1) and Experiment (E2) were conducted under similar conditions. In general, seed germination was not affected by extracts of both cover crops. However, radicle growth of all species tested (except common milkweed exposed to cowpea extract) was affected by the cover crop residue extracts. Low concentrations of hairy vetch extract stimulated the radicle growth of carrot, pepper, barnyardgrass, common milkweed, and velvetleaf. Likewise, low concentrations of cowpea extract stimulated the growth of corn, barnyardgrass, and velvetleaf. At higher concentrations all species tested were negatively affected. The order of species sensitivity to the hairy vetch extract, as determined by the IC50 (concentration required to produce 50% radicle inhibition) values, was common chickweed > redroot pigweed> barnyardgrass E1 > carrot E1 > wild carrot > corn > carrot E2 > lettuce > common milkweed > tomato > onion > barnyardgrass E2 > velvetleaf > pepper > cucumber (most sensitive to least sensitive). For cowpea the order was common chickweed > redroot pigweed > corn > tomato > lettuce > wild carrot > pepper > carrot > cucumber > onion> barnyardgrass and velvetleaf. Results suggest that the susceptibility of weeds and vegetable crops to aqueous extracts of hairy vetch and cowpea is dependent on both species and extract concentration.
Two strip tillage systems for sweet corn production were compared to conventional tillage systems in western Oregon. A power take-off rotary tiller configured to till six rows per pass was used in 1997 and 1998; a shank/coulter strip tillage machine was used in 1999 and 2000. A paired t test experimental design was used in field-scale, on-farm research with eight replications in 1997-98 and 12 replications in 1999-2000. Sweet corn was harvested using the participating growers' corn pickers and yield was determined. A subset of the participating growers recorded types of machinery and labor for tillage operations and total costs were computed for each tillage system. The rotary strip tillage system produced 900 kg·ha-1 greater corn yields (P = 0.11) than conventional tillage. The shank/coulter strip tillage system produced yields comparable to conventional tillage (P = 0.95). The rotary strip tillage system reduced total tillage costs by an average of $38.50/ha compared to conventional tillage (P = 0.03) and reduced machinery operating time by 0.59 h·ha-1 (P = 0.01). The shank/coulter strip tillage system reduced tillage costs by $36.50/ha compared to conventional tillage (P = 0.003) and reduced machinery operating time by 0.47 h·ha-1(P = 0.001). Slugs damaged corn in several strip tillage fields requiring the use of slug bait to prevent economic damage. Herbicides used in conventional tillage systems were generally effective in the strip tillage systems. Mechanical cultivation with standard cultivating equipment was more difficult in some of the strip tillage fields with heavy cover crop residue.
Abstract
Proper management of organic wastes such as crop residues, animal manures, and sewage sludges on land is essential for protecting agricultural soils from wind and water erosion, and for preventing nutrient losses through runoff. Efficient and effective use of these materials also provides one of the best means we have for maintaining soil productivity 2 by recycling plant nutrients and by improving soil physical properties. The beneficial effects of organic wastes on soil physical properties are widely known (1, 21) as evidenced by increased water infiltration, water-holding capacity, water content, aeration and permeability, soil aggregation and rooting depth, by decreased soil crusting and runoff, and by lower bulk density.