Processing tomatoes were planted on a sandy loam soil on raised beds which were prepared in a conventional method with a power bedder (PB), or with conservation tillage (CT). The CT treatments were prepared by using Glyphosate herbicide to burn-off a fall-seeded rye cover crop at either 10cm, 15cm or 30cm height. The center of the bed was tilled with a modified conservation tillage coulter caddy, prior to planting the tomatoes, to loosen the soil but leave the rye residue on the surface. Crop residue cover on the soil surface after planting the tomatoes increased from 9% in the PB treatment, to 63% with CT at 30cm. Increasing crop residue cover resulted in cooler soil temperatures during the day and warmer soil temperatures at night. Transplant survival and early growth was comparable between the tillage systems. Tomato yield was approximately 10% higher in the PB treatment than in the CT treatments. In the conservation tillage treatments, the tomato plants had lower total nitrogen concentrations in the petioles. Nitrogen immobilization by microbes in the decaying cover crop residue may have contributed to the lower petiole N concentrations, and the yield reduction.
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 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.
The availability of various conservation tillage (CT) practices along with a variety of cover residues creates an opportunity for farm managers to create new systems for vegetable production. We established various tillage practices and cover crop residues for CT use to determine which systems would continue to deliver high vegetable productivity. Recommendations for using CT based only on a yield perspective would lead us to conclude that full season crops could be grown with some form of CT and respectable yields would be obtainable. Tomato (Lycopersicon esculentum Mill.) production with CT is successfully being practiced in North Carolina in both the mountain valleys and Piedmont region. Because of the cooler soil temperatures with cover residue, summer and especially fall harvested tomatoes produce the least risk in obtaining similar yields as plow/disc production. Our experiments with short season vegetable crops and CT have had mixed results. Cole crops (Brassica L.) grown with CT in early spring or late fall experience soil temperatures cool enough to delay growth compared to plow/disc management. Proper selection of a cover crop residue type and the amount of cover residue can increase yield. Growing short season vegetable crops with CT during the warmest season of the year will reduce the risk of delayed plant growth and thus, decrease the time to harvest.
Partial steam and chemical sterilization of soil rich in organic matter increased the soil nutrients, little information exists with regard to the effect of soil solarization (SS) in this regard. A study was established to determine the effects of SS in combination with wheat residue and subsequent crop residue on increased growth response (IGR) of cole crops and soil fertility for two years. SS for 90 days increased K+, P, Ca++ and Mg++ 3 times more within five months after SS. The SS effect released higher levels of total N in the soil. However, increase levels of N was lower than that required for maximum IGR of collard. The IGR of cole crops without fertilizers was higher in SS plots as compared to bare soil. The IGR of collard was evident almost two years after SS.
The usefulness of cover crops for weed management in strawberries were evaluated. Wheat (Triticum aestevum L.), rye (Secale cereale L.), and crimson clover (Trifolium incarnatum L.) were grown in individual pots then killed by tillage or herbicide and followed in the same pots by plantings of bermuda grass [Cynodon dactylon (L.) Pers.], yellow nutsedge (Cyperus esculentus L.), crabgrass [Digitaria ischaemum (Schreb.) Schreb. ex Muhl.], or strawberries (Fragaria ×ananassa `Cardinal'). Rye and wheat tilled into the medium generally increased the growth of strawberries and decreased the growth of bermuda grass. Rye and wheat residues appeared to suppress growth of weeds and strawberries when the residues remained on the medium surface. Crimson clover had little affect on the growth of weeds or strawberries. Yellow nutsedge and crabgrass were not significantly affected by cover crop residues.
`Jewel' sweetpotato was no-till planted into crimson clover, wheat, or winter fallow. Then N was applied at 0, 60, or 120 kg·ha–1 in three equal applications to a sandy loam soil. Each fall the cover crop and production crop residue were plowed into the soil, beds were formed, and cover crops were planted. Plant growth of sweetpotato and cover crops increased with N rate. For the first 2 years crimson clover did not provide enough N (90 kg·ha–1) to compensate for the need for inorganic N. By year 3, crimson clover did provide sufficient N to produce yields sufficient to compensate for crop production and organic matter decomposition. Soil samples were taken to a depth of 1 m at the time of planting of the cover crop and production crop. Cover crops retained the N and reduced N movement into the subsoil.
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.
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).
Our farm operations will face an array of challenges over the next decade that are increasing both in scope and intensity. Global markets, global supply, competition for water, land costs driven by the value of non-agricultural use, complexity of regulation, and consumer concern over what they perceive to be safe food are among the many challenges to farm enterprise sustainability. We will have to “contain” our soil, nutrients, crop and animal residues and production inputs within our field boundaries and in the upper layers of soil. We must do all of this while increasing productivity (achieving ever-higher nutrient and crop residue flow) and being cost-competitive. Many exciting advances are being made in engineering as well as in crop genetics. The most far-reaching, however, will be the contributions that will come from other parts of the biological revolution. The science of production ecology is helping us to better understand the myriad of biological and biogeochemical processes that we deal with daily. We are moving toward management of the genetics of pest populations. We will purposefully manage the diversity and amounts of crop residues in our fields which, in turn will control the populations of plants and animals in our soil. We will manipulate the incorporation and release of nutrients from organic fractions in our soil for containment and nutrient recycling. Our nutrient and chemical inputs will be targeted and largely supplemental rather than the direct mainstay of our production. If our production is to be a sustainable part of the landscape we must be seen to provide a high level and quality of hydrological and biodiversity services as part of our management of green space. The more advanced farms have pieces of this future in place now. Numerous examples will be presented from current research, focusing heavily on crop/soil interactions.
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.