In some cases, tillage residues suc

In some cases, tillage residues such as rye can have allelopathic effects on seed germination in other crops, especially when seeds are planted directly into recently killed rye residues or some mow-killed mulches (Mitchell et al., 2000). High carbon-to-nitrogen ratios in crop residues can also cause problems such as reduced nitrogen availability (Gebhardt et al., 1985; Troeh and Thompson, 2005; Baker et al., 2007).
Some of the problems mentioned above might be more prevalent in vegetable production systems than in field crops. Successful vegetable production with conservation tillage depends on careful crop selection. Crops that germinate quickly and grow rapidly in the first few weeks after planting are more competitive with weeds than crops that initially grow slowly. Cool-season vegetables perform better in spring no-till plantings than warm-season crops (Hoyt and Konsler, 1988). The availability of specialized equipment for planting horticultural crops in no-till systems can be a limitation, but large-seeded vegetables such as sweet corn, snap beans, and squash have been successfully planted with no-till planters designed for field corn or soybean, and no-till planters for planting cabbage, broccoli, and other vegetable transplants in no-till soils have been developed (Hoyt, 1999; Peet, 2008).
The impact of reduced tillage and no-till on rates of chemical use and on nutrient leaching has been mixed because it depends on whether herbicide and pesticide uses are increased as a result of reduced tillage and how nutrients and agricultural chemicals are applied (Lal, 1991; Daverede et al., 2003). There is, however, evidence that pesticide leaching and NO3– in drainage water is higher under no-till conditions because of movement through intact macropores (Isensee and Sadeghi, 1996; Stoddard et al., 2005). In addition, higher average concentration and load of soluble phosphorus have been found in runoff water of no-till systems compared to other tillage systems (McIsaac et al., 1995). Moldboard plowing has been shown to reduce nitrogen and phosphorus runoff by redistributing the nutrients into the soil profile (Gilley et al., 2007). Similarly, Garcia et al. (2007) and Quinke et al. (2007) proposed and demonstrated a promising strategy of tilling one-time only with a moldboard plow to reduce phosphorus in runoff, followed by no-till management. They observed a significant reduction in soluble phosphorus accumulation in runoff with no negative effects on soil quality or crop yield. Further research is needed on management of no-till systems to reduce negative water quality effects.
In organic farming systems, reduced tillage raises specific challenges because the use of herbicides to kill the preceding crop is prohibited. Nonetheless, the sparse research on reduced tillage methods (strip till, ridge till, or shallow tillage) has shown promising results (Schonbeck, 2009). The choice of crop rotation, cover crop, and cover crop management is critical. Winter-hardy cover crops that are amenable to no-till, no-herbicide management can be killed by mowing or rolling in early summer. Non-winter-hardy crops planted two to three months prior to the anticipated frost-kill date can be used to form in situ mulch and suppress winter and early spring weeds. Even with the use of managed cover crops, continuous no-till does not yet appear feasible under organic systems and more research is needed in this area. A high standard of management is required to successfully implement conservation tillage practices in organic systems, and the practices need to be tailored to local soil and site conditions (Kuepper, 2001; Peigne et al., 2007).
Adoption of Conservation Tillage
The passage of the Food Security Act by Congress in 1985 tied soil conservation practices to farmer eligibility for government-sponsored crop deficiency payments, crop loans, storage payments, federal crop insurance, and disaster payments. The overall purpose of the act was to remove incentives to produce crops on highly erodible land, and the program affected more than 125 million acres nationwide. In 1990, 26 percent of planted crop acreage was under conservation tillage practices; that number rose to 41 percent in 2004 (CTIC, 2004). Among the conservation tillage practices, no-till has been used on an increasing proportion of land (from 17 million acres in 1990 to 61 million acres in 2004; Figure 3-2).
Although weed control with conventional herbicides was successfully used on millions of acres of no-till (Derksen et al., 2002) before genetically engineered (GE) crop varieties with herbicide tolerance (HT) were introduced, GE corn, soybean, and crop varieties with HT might have further encouraged the adoption of conservation tillage practices, because

FIGURE 3-2 Area of cropland in the United States managed by different tillage systems from 1990 to 2004.
SOURCE: USDA-ERS (Sandretto and Payne, 2006).
they allow farmers to replace cultivation and tillage with chemical means of controlling weeds on those major crops. USDA survey data in 1997 showed that 60 percent of the acreage planted with HT soybean was under conservation tillage compared to about 40 percent of conventional soybean. By 2008, HT soybean varieties occupied more than 92 percent of the U.S. soybean acreage, HT cotton was grown on 68 percent of the total acreage, and HT corn on 63 percent of the acreage (USDA-ERS, 2009). However, HT crops are not a prerequisite for successful herbicidal weed control in conservation tillage because many farmers still grow non-GE crops successfully with conventional herbicides. Such practices as mulching, cover cropping, and crimping or rolling crop residues also can be used with conservation tillage to suppress weeds.
Cover Cropping
Cover cropping is the practice of using vegetative crops, such as clover or vetch, to prevent soil erosion, control weeds, and provide nitrogen to a subsequent crop. Cover crops grown in rotation between cash crops provide ground cover to protect the soil. They can also be used to provide other services, notably by being tilled into the soil to maintain soil organic matter and provide nutrients to subsequent crops (green manures) or being used to trap excess nutrients in the soil profile following harvest of the primary crop to prevent leaching losses (catch crops). Perennial cover crops can be used as ground covers in orchards.
Impact of Cover Cropping
Productivity
The impact of cover crops on yields can be difficult to quantify, but some studies have shown increased yields in cash crops when they are planted after certain cover crops. Sweeney and Moyer (1994) found that when hairy vetch or red clover were grown and then used as green manure, the yield of the sorghum crops in the eastern Great Plains immediately after was 79 to 131 percent higher compared to continuous grain sorghum. Summer cover crops have been shown to produce higher yields of conventionally grown and organically grown lettuce (Ngouajio et al., 2003) and of okra (Wang et al., 2006) compared to fallow. Preliminary results from a decade-long study in south central Colorado on cover crops and crop rotations show that the yield and quality of potatoes are 12 to 30 percent higher if they were planted after sudangrass was grown and plowed in as green manure, than if they were planted after wet fallow of the plot (Delgado et al., 2008). The ability of cover crops to replace or reduce the amount of chemical nitrogen fertilizer needed when used in combination has also been well established (Kramer et al., 2002; Cherr et al., 2006).
Soil Quality
Cover crops reduce soil erosion by wind and water, and therefore decrease particulate matter in the air and sediment runoff into surface water (Langdale et al., 1991). Cover crops also add to the soil organic matter pool (Sullivan, 2004). In turn, organic matter has a profound impact on soil quality as it enhances soil structure and fertility, increases water infiltration and storage, prevents surface crusting of the soil (Roberson et al., 1995), reduces the loss of nutrients and sediment in surface runoff, and reduces leaching losses of nutrients, especially nitrogen (Brady and Weil, 2008; Plaster, 2009). Decayed root channels of cover crops alleviate soil compaction problems. Williams and Weil (2004) found that soybean yields responded the most to the preceding cover crop at the test site that was most affected by
drought and soil compaction, suggesting that the soybean plants used existing root channels to access subsoil water. Cover cropping has also been found to enhance soil microbial numbers and enzyme activities (Mullen et al., 1998; Steenwerth and Belina, 2008).
Water Quality
Cover crops increase soil biomass and therefore transpire more water, allow more rainfall to infiltrate into the soil, and decrease runoff and potential erosion to a greater extent than fallow (Dabney, 1998). Beyond taking up nutrients, cover crops also improve water quality by reducing erosion by protecting aggregates from the impacts of raindrops, reducing soil detachment and aggregate breakdown (Dabney et al., 2001).
Winter cover crops can reduce water flows, nitrate concentrations, and total nitrate load, particularly under some surface runoff or tile drainage landscapes. The effectiveness of cover crops in improving water quality varies with the growth of the cover crop, climatic conditions, and management of the main crop. More growth of the cover crop will result in greater reductions in nitrate leaching, but the growth of the cover crop can be limited by cold temperatures, water stress, nutrient availability, and delays in establishment. The lack of precipitation and soil freezing can greatly reduce NO3– leaching losses and thus reduce the impact of the cover crop. Reducing nitrogen fertilizer rates and applying nitrogen fertilizer closer to the time of crop uptake will also reduce losses from NO3– leaching and the impact of the cover crop (Kas

Hasil (Bahasa Indonesia) 1:

In some cases, tillage residues such as rye can have allelopathic effects on seed germination in other crops, especially when seeds are planted directly into recently killed rye residues or some mow-killed mulches (Mitchell et al., 2000). High carbon-to-nitrogen ratios in crop residues can also cause problems such as reduced nitrogen availability (Gebhardt et al., 1985; Troeh and Thompson, 2005; Baker et al., 2007).Some of the problems mentioned above might be more prevalent in vegetable production systems than in field crops. Successful vegetable production with conservation tillage depends on careful crop selection. Crops that germinate quickly and grow rapidly in the first few weeks after planting are more competitive with weeds than crops that initially grow slowly. Cool-season vegetables perform better in spring no-till plantings than warm-season crops (Hoyt and Konsler, 1988). The availability of specialized equipment for planting horticultural crops in no-till systems can be a limitation, but large-seeded vegetables such as sweet corn, snap beans, and squash have been successfully planted with no-till planters designed for field corn or soybean, and no-till planters for planting cabbage, broccoli, and other vegetable transplants in no-till soils have been developed (Hoyt, 1999; Peet, 2008).The impact of reduced tillage and no-till on rates of chemical use and on nutrient leaching has been mixed because it depends on whether herbicide and pesticide uses are increased as a result of reduced tillage and how nutrients and agricultural chemicals are applied (Lal, 1991; Daverede et al., 2003). There is, however, evidence that pesticide leaching and NO3– in drainage water is higher under no-till conditions because of movement through intact macropores (Isensee and Sadeghi, 1996; Stoddard et al., 2005). In addition, higher average concentration and load of soluble phosphorus have been found in runoff water of no-till systems compared to other tillage systems (McIsaac et al., 1995). Moldboard plowing has been shown to reduce nitrogen and phosphorus runoff by redistributing the nutrients into the soil profile (Gilley et al., 2007). Similarly, Garcia et al. (2007) and Quinke et al. (2007) proposed and demonstrated a promising strategy of tilling one-time only with a moldboard plow to reduce phosphorus in runoff, followed by no-till management. They observed a significant reduction in soluble phosphorus accumulation in runoff with no negative effects on soil quality or crop yield. Further research is needed on management of no-till systems to reduce negative water quality effects.Dalam sistem pertanian organik, mengurangi tanah yg dikerjakan menimbulkan tantangan khusus karena penggunaan herbisida untuk membunuh tanaman sebelumnya adalah dilarang. Meskipun demikian, penelitian jarang pada metode mengurangi tanah yg dikerjakan (strip sampai, ridge sampai atau dangkal budidaya) telah menunjukkan hasil yang menjanjikan (Schonbeck, 2009). Pilihan manajemen rotasi tanaman, tanaman penutup, dan tanaman cover crop sangat penting. Musim dingin-hardy tanaman penutup yang setuju untuk no-sampai, no-herbisida manajemen dapat dibunuh dengan memotong atau bergulir di awal musim panas. Bebas-musim dingin-hardy tanaman ditanam dua sampai tiga bulan sebelum tanggal embun beku-membunuh diantisipasi dapat digunakan untuk membentuk di situ Mulsa dan menekan musim dingin dan awal musim semi gulma. Bahkan dengan penggunaan dikelola tanaman penutup, terus-menerus no-sampai tidak lagi muncul layak di bawah sistem organik dan penelitian lebih lanjut diperlukan di daerah ini. Standar yang tinggi dari manajemen diperlukan untuk berhasil melaksanakan praktek konservasi tanah yg dikerjakan di sistem organik, dan praktek-praktek perlu disesuaikan lokal tanah dan kondisi situs (Kuepper, 2001; Peigne et al., 2007).Adopsi konservasi tanah yg dikerjakanThe passage of the Food Security Act by Congress in 1985 tied soil conservation practices to farmer eligibility for government-sponsored crop deficiency payments, crop loans, storage payments, federal crop insurance, and disaster payments. The overall purpose of the act was to remove incentives to produce crops on highly erodible land, and the program affected more than 125 million acres nationwide. In 1990, 26 percent of planted crop acreage was under conservation tillage practices; that number rose to 41 percent in 2004 (CTIC, 2004). Among the conservation tillage practices, no-till has been used on an increasing proportion of land (from 17 million acres in 1990 to 61 million acres in 2004; Figure 3-2).Although weed control with conventional herbicides was successfully used on millions of acres of no-till (Derksen et al., 2002) before genetically engineered (GE) crop varieties with herbicide tolerance (HT) were introduced, GE corn, soybean, and crop varieties with HT might have further encouraged the adoption of conservation tillage practices, because FIGURE 3-2 Area of cropland in the United States managed by different tillage systems from 1990 to 2004.SOURCE: USDA-ERS (Sandretto and Payne, 2006).they allow farmers to replace cultivation and tillage with chemical means of controlling weeds on those major crops. USDA survey data in 1997 showed that 60 percent of the acreage planted with HT soybean was under conservation tillage compared to about 40 percent of conventional soybean. By 2008, HT soybean varieties occupied more than 92 percent of the U.S. soybean acreage, HT cotton was grown on 68 percent of the total acreage, and HT corn on 63 percent of the acreage (USDA-ERS, 2009). However, HT crops are not a prerequisite for successful herbicidal weed control in conservation tillage because many farmers still grow non-GE crops successfully with conventional herbicides. Such practices as mulching, cover cropping, and crimping or rolling crop residues also can be used with conservation tillage to suppress weeds.Cover CroppingCover cropping is the practice of using vegetative crops, such as clover or vetch, to prevent soil erosion, control weeds, and provide nitrogen to a subsequent crop. Cover crops grown in rotation between cash crops provide ground cover to protect the soil. They can also be used to provide other services, notably by being tilled into the soil to maintain soil organic matter and provide nutrients to subsequent crops (green manures) or being used to trap excess nutrients in the soil profile following harvest of the primary crop to prevent leaching losses (catch crops). Perennial cover crops can be used as ground covers in orchards.Impact of Cover CroppingProductivityThe impact of cover crops on yields can be difficult to quantify, but some studies have shown increased yields in cash crops when they are planted after certain cover crops. Sweeney and Moyer (1994) found that when hairy vetch or red clover were grown and then used as green manure, the yield of the sorghum crops in the eastern Great Plains immediately after was 79 to 131 percent higher compared to continuous grain sorghum. Summer cover crops have been shown to produce higher yields of conventionally grown and organically grown lettuce (Ngouajio et al., 2003) and of okra (Wang et al., 2006) compared to fallow. Preliminary results from a decade-long study in south central Colorado on cover crops and crop rotations show that the yield and quality of potatoes are 12 to 30 percent higher if they were planted after sudangrass was grown and plowed in as green manure, than if they were planted after wet fallow of the plot (Delgado et al., 2008). The ability of cover crops to replace or reduce the amount of chemical nitrogen fertilizer needed when used in combination has also been well established (Kramer et al., 2002; Cherr et al., 2006).Soil QualityCover crops reduce soil erosion by wind and water, and therefore decrease particulate matter in the air and sediment runoff into surface water (Langdale et al., 1991). Cover crops also add to the soil organic matter pool (Sullivan, 2004). In turn, organic matter has a profound impact on soil quality as it enhances soil structure and fertility, increases water infiltration and storage, prevents surface crusting of the soil (Roberson et al., 1995), reduces the loss of nutrients and sediment in surface runoff, and reduces leaching losses of nutrients, especially nitrogen (Brady and Weil, 2008; Plaster, 2009). Decayed root channels of cover crops alleviate soil compaction problems. Williams and Weil (2004) found that soybean yields responded the most to the preceding cover crop at the test site that was most affected bydrought and soil compaction, suggesting that the soybean plants used existing root channels to access subsoil water. Cover cropping has also been found to enhance soil microbial numbers and enzyme activities (Mullen et al., 1998; Steenwerth and Belina, 2008).Water QualityCover crops increase soil biomass and therefore transpire more water, allow more rainfall to infiltrate into the soil, and decrease runoff and potential erosion to a greater extent than fallow (Dabney, 1998). Beyond taking up nutrients, cover crops also improve water quality by reducing erosion by protecting aggregates from the impacts of raindrops, reducing soil detachment and aggregate breakdown (Dabney et al., 2001).Winter cover crops can reduce water flows, nitrate concentrations, and total nitrate load, particularly under some surface runoff or tile drainage landscapes. The effectiveness of cover crops in improving water quality varies with the growth of the cover crop, climatic conditions, and management of the main crop. More growth of the cover crop will result in greater reductions in nitrate leaching, but the growth of the cover crop can be limited by cold temperatures, water stress, nutrient availability, and delays in establishment. The lack of precipitation and soil freezing can greatly reduce NO3– leaching losses and thus reduce the impact of the cover crop. Reducing nitrogen fertilizer rates and applying nitrogen fertilizer closer to the time of crop uptake will also reduce losses from NO3– leaching and the impact of the cover crop (Kas