percent of the soil surface covered

percent of the soil surface covered from harvest to planting, depending on the crop residue, because it uses specifically designed seed planters or drills to penetrate all remaining surface residues (Huggins and Reganold, 2008). Comparisons of conventional tillage practices to conservation tillage in corn, soybean, and winter wheat found that systems that use conservation tillage tend to use more herbicides for each crop, but less insecticides (USDA-ERS, 2005).
Impact of Conservation Tillage
Physical Properties of Soil
Soil under no-till management has been shown to have a higher proportion of water stable aggregates (Karlen et al., 1994a; Abid and Lal, 2008), and the aggregates have larger geometric mean diameter and mean weight diameter compared to chisel-plowed soil (Abid and Lal, 2008). The large aggregates contain finer soil textures that assist in retaining more water than small aggregates. Arshad et al. (1999) compiled data collected from two sites in northern British Columbia to ascertain the long-term effects of conventional tillage and no-till on soil components thought to be important in surface soil structural improvement. They observed that soil water retention was greater under no-till compared with conventional till without dramatically altering bulk density because of redistribution of pore size classes into more small pores and less large pores.
No-till and other conservation tillage systems can work in a wide range of climates, soils, and geographic areas. Continuous no-till is also applicable to most crops, with the notable exceptions of wetland rice and root crops, such as potatoes. However, no-till crop production on fine-textured, poorly drained soils can be problematic and often results in decreased yields. Yields of no-till corn, for instance, are often reduced by 5 to 10 percent on those kinds of soils, compared with yields with conventional tillage, particularly in northern regions. Because the crop residue blocks the sun’s rays from warming the earth to the same degree as occurs with conventional tillage, soil temperatures are colder in the spring, which can slow seed germination and curtail the early growth of warm-season crops, such as corn, in northern latitudes (Huggins and Reganold, 2008).
Soil Organic Matter
The amount of organic matter in soil subject to conventional tillage has been compared to soil subject to conservation tillage or no-till in different locations. Dell et al. (2008) quantified the impacts of no-till and rye (Secale cereale L.) cover crops on soil carbon and physical properties. They found that the no-till fields had 50 percent more carbon particulate and mineral-associated pools in the upper 5 cm compared to conventional tillage. The sizes of the carbon pools below 5 cm in the two fields were similar. The stability of the soil aggregates is proportional to the carbon pool size. Another study by Motta et al. (2007) compared soil organic carbon at different depths of the soil in cotton fields subject to conventional tillage and no-till. They found that the no-till fields had much higher particulate organic carbon within the top 3 cm. Some scientists have questioned if substantial soil carbon sequestration can be accomplished by changing from conventional plowing to conservation tillage. Baker et al. (2007b) argued that soils were sampled to a depth of 30 cm or less in essentially all cases where conservation tillage was found to sequester carbon. In the few studies where sampling extended deeper than 30 cm, conservation tillage has shown no consistent accrual of soil organic carbon. Instead conservation tillage showed a difference in the distribution of soil organic carbon, with higher concentrations near the surface in conservation tillage and higher concentrations in deeper layers under conventional tillage. Blanco-Canqui and Lal (2008) assessed the impacts of long-term no-till and plow-based cropping systems on soil carbon sequestration in the top 60 cm of soils across Kentucky, Ohio, and Pennsylvania. They found that no-till farming increased organic carbon concentrations in the upper layers of some soils, but it did not store more organic carbon than plowed soils for the whole soil profile. In fact, total soil profile organic carbon was significantly higher in plowed-based soils in a number of the areas sampled. In another study, Christopher et al. (2009) found that the soil organic carbon pool in the whole soil profile (0–60 cm) was never greater in no-till than conventionally tilled fields across 12 contrasting but representative soils in the Midwestern United States and was actually lower in the no-till soils in some areas.
Soil Microbial Activity and Diversity
Bacteria, fungi, and nematodes are important in maintaining the physical structure of soil. In a study of soil quality with data collected following a long-term tillage study on continuous corn, Karlen et al. (1994a) found that plots managed using no-till practices have higher microbial activity and earthworm populations. Motta et al. (2007) also found higher microbial biomass in no-till cotton fields compared to conventional-till ones.
Soil Erosion
The greater the percentage of ground cover (residue or mulch), the lower is the soil loss ratio (Figure 3-1) due to water and wind. The soil loss ratio (SLR) is an estimate of the ratio of soil loss under actual conditions to losses experienced under the reference condition of clean-tilled continuous-fallow conditions (the reference condition). Leaving 30 percent of the soil surface covered with residue, as with conservation tillage, reduces erosion by half as compared with bare, fallow soil. Leaving 50 to 100 percent of the surface covered throughout the year, as no-till does, reduces soil erosion dramatically.
Montgomery (2007) looked at numerous studies on conventional (n = 448) and conservation (n = 47) agricultural systems and found an average net soil loss of 3.9 mm/yr under conventional agriculture and 0.12 under conservation agriculture that included conservation tillage, no-till methods, and terracing. Montgomery further examined 39 studies involving direct comparisons of soil erosion under conventional and no-till methods representing a wide variety of settings with different erosion rates and showed that no-till practices reduce soil erosion up to 1,000 times, enough to bring agricultural erosion rates into line with rates of soil production.


Sediment Loading and Water Quality
Agriculture is a major contributor to sediment pollution, primarily because of improper farming practices that increase soil erosion. Farming on steep slopes, excessive heavy tillage, and lack of conservation practices are principal causes. A number of studies document the effectiveness of conservation or no-till on reducing sediment in runoff. Blevins et al. (1990) compared the contributions of no-till, chisel-plow tillage, and conventional tillage systems used in corn production to sediment losses and surface runoff on a Maury silt loam. Over a four-year period, they measured soil losses of 20, 0.71, and 0.55 Mg/ha from conventional, chisel-plow, and no-till systems, respectively. Amounts of nitrate (NO3–), soluble phosphorus, and atrazine leaving the plots in surface runoff were greatest from conventional tillage and about equal from chisel-plow and no-till. Chichester and Richardson (1992) compared the effect of no-till and conventional chisel-till soil management on runoff

FIGURE 3-1 Soil loss ratio and percent ground cover.
SOURCE: McCarthy et al. (1993). Reprinted with permission from the University of Missouri Extension.
water volumes, sediment loss, and nitrogen and phosphorus loss from small watersheds on a clay soil. They found that runoff volume was not changed by tillage system, but sediment loss and nitrogen and phosphorus losses in runoff were far less, on average, from no-till than from chisel-till. Average annual quantities for sediment and nutrient losses were: 160 kg/ha and 1575 kg/ha for sediment, 3.8 kg/ha and 8.1 kg/ha for nitrogen, and 0.8 kg/ha and 1.5 kg/ha for phosphorus for no-till and chisel-till, respectively. Although erosion remains a significant problem in the United States, conservation and tillage changes have resulted in substantial improvements over the last 30 years. Soil erosion on cropland declined, as a result of changes in tillage practices and land retirement, from 3.1 billion tons per year in 1982 to 1.8 billion tons per year in 2001, while sheet and rill erosion dropped by almost 41 percent, and wind erosion dropped by 43 percent during the same time period (NRI, 2003).
Air Quality
With the advent of reduced and “zero” tillage in the past few decades made possible through the use of herbicides, releases of carbon dioxide (CO2), nitrous oxide (N2O), and particulate matter from agricultural soil have been reduced (Robertson et al., 2000; Madden et al., 2008). Reduced tillage reversed some of the soil carbon decline in surface soils. The impacts of tillage and different cropping systems on soil carbon (discussed earlier in this chapter) can be translated with reasonable accuracy into changes in CO2 flux over time. When CO2 flux is calculated and N2O and methane (CH4) fluxes are measured, the overall atmospheric impact of production systems can be assessed. Unfortunately, there are few production systems where such gaseous flux measurements have been done over a sufficient time span. One of the best sources of data comes from the Long Term Ecological Research (LTER) sites funded by the National Science Foundation (NSF). The LTER data in Box 3-1 are presented not to represent overall U.S. agricultural fluxes, but rather to show comparisons for the predominant gases between natural and managed systems, and the contribution of key management practices. The net greenhouse-gas emissions from agriculture in the United States were estimated to be about 50 g of CO2 equivalent/m2 per year (West and Marland, 2002). That estima

Hasil (Bahasa Indonesia) 1:

persen dari permukaan tanah yang tertutup dari panen untuk penanaman, tergantung pada residu tanaman, karena menggunakan khusus dirancang bibit pekebun atau latihan untuk menembus semua residu permukaan tersisa (Huggins dan Reganold, 2008). Perbandingan dari praktek-praktek budidaya konvensional untuk konservasi tanah yg dikerjakan dalam jagung, kedelai, dan gandum musim dingin ditemukan bahwa sistem yang menggunakan konservasi budidaya cenderung menggunakan lebih herbisida untuk setiap tanaman, tapi kurang insektisida (USDA-ERS, 2005).Dampak dari konservasi tanah yg dikerjakanSifat fisik dari tanahTanah di bawah manajemen no-sampai telah ditunjukkan untuk memiliki proporsi yang lebih tinggi dari air stabil agregat (Karlen et al., 1994a; Abid dan Lal, 2008), dan agregat memiliki diameter purata geometris yang lebih besar dan berat badan rata-rata diameter dibandingkan dengan pahat yang dibajak tanah (Abid dan Lal, 2008). Agregat besar berisi tekstur tanah yang lebih halus yang membantu dalam mempertahankan lebih banyak air daripada kecil agregat. Arshad et al. (1999) dikompilasi data yang dikumpulkan dari dua situs di northern British Columbia untuk memastikan jangka panjang budidaya konvensional dan no-sampai pada komponen tanah yang dianggap penting dalam perbaikan struktural permukaan tanah. Mereka mengamati bahwa retensi air tanah adalah lebih besar di bawah no-sampai dibandingkan dengan konvensional sampai tanpa secara dramatis mengubah kepadatan massal karena redistribusi pori-pori ukuran kelas ke dalam pori-pori lebih kecil dan kurang pori-pori besar.No-sampai dan lain konservasi tanah yg dikerjakan sistem dapat bekerja di berbagai iklim, tanah dan wilayah geografis. Terus-menerus no-sampai ini juga berlaku untuk sebagian besar tanaman, dengan pengecualian beras basah dan akar tanaman, seperti kentang. Namun, no-sampai tanaman di tanah bertekstur halus, buruk dikeringkan dapat bermasalah dan sering mengakibatkan penurunan hasil. Hasil no-sampai jagung, misalnya, sering dikurangi oleh 5 sampai 10 persen pada orang-orang macam tanah, dibandingkan dengan hasil panen dengan tanah yg dikerjakan konvensional, khususnya di wilayah utara. Karena residu tanaman blok sinar matahari dari pemanasan bumi derajat yang sama sebagai terjadi dengan konvensional tanah yg dikerjakan, tanah suhu dingin di musim semi, yang dapat memperlambat daya berkecambah dan membatasi pertumbuhan awal musim hangat tanaman, seperti jagung, di lintang utara (Huggins dan Reganold, 2008).Bahan organik tanahThe amount of organic matter in soil subject to conventional tillage has been compared to soil subject to conservation tillage or no-till in different locations. Dell et al. (2008) quantified the impacts of no-till and rye (Secale cereale L.) cover crops on soil carbon and physical properties. They found that the no-till fields had 50 percent more carbon particulate and mineral-associated pools in the upper 5 cm compared to conventional tillage. The sizes of the carbon pools below 5 cm in the two fields were similar. The stability of the soil aggregates is proportional to the carbon pool size. Another study by Motta et al. (2007) compared soil organic carbon at different depths of the soil in cotton fields subject to conventional tillage and no-till. They found that the no-till fields had much higher particulate organic carbon within the top 3 cm. Some scientists have questioned if substantial soil carbon sequestration can be accomplished by changing from conventional plowing to conservation tillage. Baker et al. (2007b) argued that soils were sampled to a depth of 30 cm or less in essentially all cases where conservation tillage was found to sequester carbon. In the few studies where sampling extended deeper than 30 cm, conservation tillage has shown no consistent accrual of soil organic carbon. Instead conservation tillage showed a difference in the distribution of soil organic carbon, with higher concentrations near the surface in conservation tillage and higher concentrations in deeper layers under conventional tillage. Blanco-Canqui and Lal (2008) assessed the impacts of long-term no-till and plow-based cropping systems on soil carbon sequestration in the top 60 cm of soils across Kentucky, Ohio, and Pennsylvania. They found that no-till farming increased organic carbon concentrations in the upper layers of some soils, but it did not store more organic carbon than plowed soils for the whole soil profile. In fact, total soil profile organic carbon was significantly higher in plowed-based soils in a number of the areas sampled. In another study, Christopher et al. (2009) found that the soil organic carbon pool in the whole soil profile (0–60 cm) was never greater in no-till than conventionally tilled fields across 12 contrasting but representative soils in the Midwestern United States and was actually lower in the no-till soils in some areas.Soil Microbial Activity and DiversityBacteria, fungi, and nematodes are important in maintaining the physical structure of soil. In a study of soil quality with data collected following a long-term tillage study on continuous corn, Karlen et al. (1994a) found that plots managed using no-till practices have higher microbial activity and earthworm populations. Motta et al. (2007) also found higher microbial biomass in no-till cotton fields compared to conventional-till ones.Soil ErosionThe greater the percentage of ground cover (residue or mulch), the lower is the soil loss ratio (Figure 3-1) due to water and wind. The soil loss ratio (SLR) is an estimate of the ratio of soil loss under actual conditions to losses experienced under the reference condition of clean-tilled continuous-fallow conditions (the reference condition). Leaving 30 percent of the soil surface covered with residue, as with conservation tillage, reduces erosion by half as compared with bare, fallow soil. Leaving 50 to 100 percent of the surface covered throughout the year, as no-till does, reduces soil erosion dramatically.Montgomery (2007) looked at numerous studies on conventional (n = 448) and conservation (n = 47) agricultural systems and found an average net soil loss of 3.9 mm/yr under conventional agriculture and 0.12 under conservation agriculture that included conservation tillage, no-till methods, and terracing. Montgomery further examined 39 studies involving direct comparisons of soil erosion under conventional and no-till methods representing a wide variety of settings with different erosion rates and showed that no-till practices reduce soil erosion up to 1,000 times, enough to bring agricultural erosion rates into line with rates of soil production.Sediment Loading and Water QualityAgriculture is a major contributor to sediment pollution, primarily because of improper farming practices that increase soil erosion. Farming on steep slopes, excessive heavy tillage, and lack of conservation practices are principal causes. A number of studies document the effectiveness of conservation or no-till on reducing sediment in runoff. Blevins et al. (1990) compared the contributions of no-till, chisel-plow tillage, and conventional tillage systems used in corn production to sediment losses and surface runoff on a Maury silt loam. Over a four-year period, they measured soil losses of 20, 0.71, and 0.55 Mg/ha from conventional, chisel-plow, and no-till systems, respectively. Amounts of nitrate (NO3–), soluble phosphorus, and atrazine leaving the plots in surface runoff were greatest from conventional tillage and about equal from chisel-plow and no-till. Chichester and Richardson (1992) compared the effect of no-till and conventional chisel-till soil management on runoff FIGURE 3-1 Soil loss ratio and percent ground cover.SOURCE: McCarthy et al. (1993). Reprinted with permission from the University of Missouri Extension.water volumes, sediment loss, and nitrogen and phosphorus loss from small watersheds on a clay soil. They found that runoff volume was not changed by tillage system, but sediment loss and nitrogen and phosphorus losses in runoff were far less, on average, from no-till than from chisel-till. Average annual quantities for sediment and nutrient losses were: 160 kg/ha and 1575 kg/ha for sediment, 3.8 kg/ha and 8.1 kg/ha for nitrogen, and 0.8 kg/ha and 1.5 kg/ha for phosphorus for no-till and chisel-till, respectively. Although erosion remains a significant problem in the United States, conservation and tillage changes have resulted in substantial improvements over the last 30 years. Soil erosion on cropland declined, as a result of changes in tillage practices and land retirement, from 3.1 billion tons per year in 1982 to 1.8 billion tons per year in 2001, while sheet and rill erosion dropped by almost 41 percent, and wind erosion dropped by 43 percent during the same time period (NRI, 2003).Air QualityWith the advent of reduced and “zero” tillage in the past few decades made possible through the use of herbicides, releases of carbon dioxide (CO2), nitrous oxide (N2O), and particulate matter from agricultural soil have been reduced (Robertson et al., 2000; Madden et al., 2008). Reduced tillage reversed some of the soil carbon decline in surface soils. The impacts of tillage and different cropping systems on soil carbon (discussed earlier in this chapter) can be translated with reasonable accuracy into changes in CO2 flux over time. When CO2 flux is calculated and N2O and methane (CH4) fluxes are measured, the overall atmospheric impact of production systems can be assessed. Unfortunately, there are few production systems where such gaseous flux measurements have been done over a sufficient time span. One of the best sources of data comes from the Long Term Ecological Research (LTER) sites funded by the National Science Foundation (NSF). The LTER data in Box 3-1 are presented not to represent overall U.S. agricultural fluxes, but rather to show comparisons for the predominant gases between natural and managed systems, and the contribution of key management practices. The net greenhouse-gas emissions from agriculture in the United States were estimated to be about 50 g of CO2 equivalent/m2 per year (West and Marland, 2002). That estima

Hasil (Bahasa Indonesia) 2:

persen dari permukaan tanah tertutup dari panen untuk penanaman, tergantung pada sisa tanaman, karena menggunakan khusus dirancang pekebun biji atau latihan untuk menembus semua residu permukaan yang tersisa (Huggins dan Reganold, 2008). Perbandingan persiapan lahan praktek konvensional untuk konservasi tanah pada jagung, kedelai, dan gandum musim dingin menemukan bahwa sistem yang menggunakan konservasi tanah cenderung menggunakan lebih herbisida untuk setiap tanaman, tetapi kurang insektisida (USDA-ERS, 2005).
Dampak Konservasi tillage
Fisik Sifat tanah
tanah di bawah tidak-sampai manajemen telah terbukti memiliki proporsi yang lebih tinggi dari air agregat stabil (Karlen et al, 1994a;. Abid dan Lal, 2008), dan agregat memiliki lebih besar diameter rata geometris dan berarti diameter berat dibandingkan dengan chisel- membajak tanah (Abid dan Lal, 2008). Agregat besar berisi tekstur tanah halus yang membantu dalam mempertahankan lebih banyak air daripada agregat kecil. Arshad et al. (1999) data yang dikumpulkan dikumpulkan dari dua lokasi di utara British Columbia untuk memastikan efek jangka panjang dari pengolahan tanah konvensional dan tidak-sampai pada komponen tanah dianggap penting dalam perbaikan struktur tanah permukaan. Mereka mengamati bahwa retensi air tanah lebih besar di bawah tidak-sampai dibandingkan dengan konvensional sampai tanpa secara dramatis mengubah bulk density karena redistribusi kelas ukuran pori dalam pori-pori lebih kecil dan pori-pori kurang besar.
Tidak ada-sampai dan sistem pengolahan tanah konservasi lainnya dapat bekerja di berbagai berbagai iklim, tanah, dan wilayah geografis. Tidak-sampai terus menerus juga berlaku untuk sebagian besar tanaman, dengan pengecualian dari lahan basah beras dan tanaman akar, seperti kentang. Namun, tidak ada-sampai produksi tanaman di fine-bertekstur, tanah buruk dikeringkan dapat menjadi masalah dan sering mengakibatkan hasil menurun. Hasil dari tidak-sampai jagung, misalnya, sering turun 5 sampai 10 persen pada orang-orang jenis tanah, dibandingkan dengan hasil dengan pengolahan tanah konvensional, terutama di wilayah utara. Karena blok sisa tanaman sinar matahari dari pemanasan bumi ke tingkat yang sama seperti yang terjadi dengan pengolahan tanah konvensional, suhu tanah yang dingin di musim semi, yang dapat memperlambat perkecambahan benih dan mengurangi pertumbuhan awal hangat-musim panen, seperti jagung, di lintang utara (Huggins dan Reganold, 2008).
Tanah Bahan Organik
Jumlah bahan organik dalam subjek tanah untuk pengolahan tanah konvensional telah dibandingkan dengan subjek tanah untuk konservasi tanah atau tidak-sampai di lokasi yang berbeda. Dell et al. (2008) dihitung dampak tidak-sampai dan rye (Secale cereale L.) tanaman penutup pada karbon tanah dan sifat fisik. Mereka menemukan bahwa tidak ada-sampai bidang memiliki partikel karbon 50 persen lebih dan kolam-mineral terkait di atas 5 cm dibandingkan dengan pengolahan tanah konvensional. Ukuran kolam karbon di bawah 5 cm di dua bidang yang sama. Stabilitas agregat tanah sebanding dengan ukuran kolam karbon. Studi lain oleh Motta et al. (2007) dibandingkan karbon organik tanah pada kedalaman yang berbeda dari tanah di ladang kapas tunduk pengolahan tanah konvensional dan tidak-sampai. Mereka menemukan bahwa tidak ada-sampai bidang memiliki jauh lebih tinggi partikulat karbon organik dalam top 3 cm. Beberapa ilmuwan telah mempertanyakan jika penyerapan karbon tanah substansial dapat dicapai dengan mengubah dari membajak konvensional untuk konservasi tanah. Baker et al. (2007b) berpendapat bahwa tanah yang sampel dengan kedalaman 30 cm atau kurang dalam dasarnya semua kasus di mana konservasi tanah ditemukan untuk menyerap karbon. Dalam beberapa penelitian di mana sampel diperpanjang lebih dari 30 cm, konservasi tanah tidak menunjukkan akrual konsisten karbon organik tanah. Sebaliknya konservasi tanah menunjukkan perbedaan dalam distribusi karbon organik tanah, dengan konsentrasi yang lebih tinggi di dekat permukaan di konservasi tanah dan konsentrasi yang lebih tinggi di lapisan yang lebih dalam di bawah tanah yg dikerjakan konvensional. Blanco-Canqui dan Lal (2008) menilai dampak jangka panjang tidak-sampai dan sistem tanam pada penyerapan karbon tanah membajak berbasis di atas 60 cm dari tanah seberang Kentucky, Ohio, dan Pennsylvania. Mereka menemukan bahwa tidak ada-sampai petani peningkatan konsentrasi karbon organik di lapisan atas dari beberapa tanah, tetapi tidak menyimpan lebih banyak karbon organik dari tanah dibajak untuk profil tanah keseluruhan. Bahkan, jumlah profil karbon organik tanah secara signifikan lebih tinggi di tanah berbasis dibajak di sejumlah daerah sampel. Dalam studi lain, Christopher et al. (2009) menemukan bahwa kolam karbon organik tanah dalam profil seluruh tanah (0-60 cm) tidak pernah lebih besar tidak-sampai dari bidang konvensional digarap di 12 kontras tetapi tanah perwakilan di Amerika Serikat Midwestern dan benar-benar lebih rendah tidak dengan tanah -till di beberapa daerah.
Tanah Mikroba Aktivitas dan Keanekaragaman
Bakteri, jamur, dan nematoda yang penting dalam mempertahankan struktur fisik tanah. Dalam sebuah studi dari kualitas tanah dengan data yang dikumpulkan setelah studi persiapan lahan jangka panjang pada jagung terus menerus, Karlen et al. (1994a) menemukan bahwa plot berhasil menggunakan no-sampai praktek memiliki aktivitas mikroba lebih tinggi dan populasi cacing tanah. Motta et al. (2007) juga menemukan biomassa mikroba lebih tinggi tidak-sampai kapas bidang dibandingkan dengan yang konvensional-sampai.
Erosi Tanah
Semakin besar persentase penutup tanah (residu atau mulsa), semakin rendah rasio loss tanah (Gambar 3-1) karena air dan angin. Loss ratio tanah (SLR) adalah perkiraan rasio kehilangan tanah dalam kondisi yang sebenarnya untuk kerugian yang dialami di bawah kondisi referensi dari kondisi terus-bera bersih-digarap (kondisi referensi). Meninggalkan 30 persen dari permukaan tanah ditutupi dengan residu, seperti konservasi tanah, mengurangi erosi dengan setengah dibandingkan dengan telanjang, tanah bera. Meninggalkan 50 sampai 100 persen dari permukaan tertutup sepanjang tahun, karena tidak ada-sampai tidak, mengurangi erosi tanah secara dramatis.
Montgomery (2007) melihat banyak penelitian pada konvensional (n = 448) dan konservasi (n = 47) sistem pertanian dan menemukan kerugian rata-rata bersih tanah 3,9 mm / tahun di bawah pertanian konvensional dan 0,12 di bawah pertanian konservasi yang termasuk konservasi tanah, tidak-sampai metode, dan terasering. Montgomery lanjut diperiksa 39 studi yang melibatkan perbandingan langsung dari erosi tanah di bawah konvensional dan tidak-sampai metode yang mewakili berbagai pengaturan dengan tingkat erosi yang berbeda dan menunjukkan bahwa tidak ada-sampai praktek mengurangi erosi tanah hingga 1.000 kali, cukup untuk membawa tingkat erosi pertanian menjadi Sejalan dengan tingkat produksi tanah. Memuat Sedimen dan Kualitas Air Pertanian merupakan penyumbang utama pencemaran sedimen, terutama karena praktek pertanian yang tidak tepat yang meningkatkan erosi tanah. Pertanian di lereng curam, pengolahan tanah berat yang berlebihan, dan kurangnya praktik konservasi adalah penyebab utama. Sejumlah penelitian mendokumentasikan efektivitas konservasi atau tidak-sampai pada pengurangan sedimen di limpasan. Blevins dkk. (1990) dibandingkan kontribusi dari tidak-sampai, pahat-bajak persiapan lahan, dan sistem pengolahan tanah konvensional yang digunakan dalam produksi jagung sedimen kerugian dan aliran permukaan pada Maury lumpur tanah liat. Selama periode empat tahun, mereka mengukur kerugian tanah 20, 0,71, dan 0,55 Mg / ha dari konvensional, pahat-bajak, dan tidak-sampai sistem, masing-masing. Jumlah nitrat (NO3-), fosfor larut, dan atrazin meninggalkan plot di aliran permukaan yang terbesar dari pengolahan tanah konvensional dan sekitar sama dari pahat-bajak dan tidak-sampai. Chichester dan Richardson (1992) membandingkan efek dari tidak-sampai dan konvensional pahat-sampai pengelolaan tanah pada limpasan GAMBAR 3-1 Tanah loss ratio dan penutup persen tanah. SUMBER: McCarthy et al. (1993). Dicetak ulang dengan izin dari University of Missouri Extension. Volume air, kehilangan sedimen, dan nitrogen dan fosfor dari hilangnya air kecil pada tanah lempung. Mereka menemukan bahwa volume yang limpasan tidak berubah oleh sistem pengolahan tanah, namun kerugian kehilangan sedimen dan nitrogen dan fosfor dalam limpasan yang jauh lebih sedikit, rata-rata, dari tidak-sampai daripada dari pahat-sampai. Jumlah rata-rata tahunan untuk kerugian sedimen dan nutrisi adalah: 160 kg / ha dan 1.575 kg / ha untuk sedimen, 3,8 kg / ha dan 8,1 kg / ha untuk nitrogen, dan 0,8 kg / ha dan 1,5 kg / ha untuk fosfor untuk tidak-sampai dan pahat-sampai, masing-masing. Meskipun erosi tetap menjadi masalah yang signifikan di Amerika Serikat, perubahan konservasi dan pengolahan tanah telah menghasilkan peningkatan yang besar selama 30 tahun terakhir. Erosi tanah pada lahan pertanian menurun, sebagai akibat dari perubahan dalam praktek pengolahan dan pensiun tanah, dari 3,1 miliar ton per tahun di 1982-1800000000 ton per tahun pada tahun 2001, sementara lembar dan rill erosi turun hampir 41 persen, dan erosi angin turun 43 persen selama periode waktu yang sama (NRI 2003). Kualitas Air Dengan munculnya berkurang dan "nol" pengolahan dalam beberapa dekade terakhir dimungkinkan melalui penggunaan herbisida, siaran karbon dioksida (CO2), nitrogen oksida ( N2O), dan partikel dari tanah pertanian telah berkurang (Robertson et al, 2000;. Madden et al, 2008).. Mengurangi pengolahan terbalik beberapa penurunan karbon tanah di tanah permukaan. Dampak pengolahan tanah dan sistem tanam yang berbeda pada karbon tanah (dibahas sebelumnya dalam bab ini) dapat diterjemahkan dengan cukup akurat dalam perubahan CO2 fluks dari waktu ke waktu. Ketika CO2 fluks dihitung dan N2O dan metana (CH4) fluks diukur, dampak atmosfer keseluruhan sistem produksi dapat dinilai. Sayangnya, ada beberapa sistem produksi di mana seperti pengukuran fluks gas telah dilakukan selama rentang waktu yang cukup. Salah satu sumber terbaik data berasal dari Long Term Ecological Research (LTER) situs didanai oleh National Science Foundation (NSF). Data LTER di Box 3-1 disajikan tidak mewakili keseluruhan fluks pertanian AS, melainkan untuk menunjukkan perbandingan untuk gas dominan antara sistem alam dan dikelola, dan kontribusi dari praktek manajemen kunci. Emisi gas rumah kaca bersih dari pertanian di Amerika Serikat yang diperkirakan sekitar 50 g CO2 ekuivalen / m2 per tahun (Barat dan Marland, 2002). Estima yang