| Native Cerrado |
NC |
Fragment of Cerrado (strict sense), without signs of anthropic disturbance, characterized by the presence of small, twisted trees and grasses covering the soil. This area was considered as a control for the comparison with the tillage systems. |
| Minimum tillage I |
MT I |
The Cerrado was deforested in 1977, with subsequent cultivation of rice/soybean for 3 years under conventional tillage and, until the 1999/00 season, soybean/corn was cultivated in rotation under conventional tillage, disturbing the soil with heavy harrowing with discs of 32" every 3 years. In 2000/02, cotton was cultivated, followed by gypsum application, two harrowings (32") and seeding of millet in the off-season. In 2002/03, gypsum was applied and the soil was prepared with scarification until 0.30 m, two harrowings (32"), and soybean and corn were sown in the off-season. In 2003/04, gypsum was applied broadcast and cotton was cultivated on corn residues with later destruction of stumps, combining mechanical mowing and a light harrowing to incorporate plant residues. In 2004/07, gypsum was applied, a leveling harrow was used and soybean and millet were cultivated in the off-season. In 2007/08, there were gypsum application, two harrowings (32"), scarification until 0.30 m and cultivation of soybean and corn. In 2008/10, gypsum was applied, a light harrow was used and soybean and corn were cultivated in the off-season. All the fertilizations were performed in the seeding row and followed the technical recommendations for the crops, as also occurred in the systems MT II and MT II, which are described below. Therefore, only in the last two crop seasons there was lower disturbance on soil surface, with a light harrowing before soybean sowing. |
| Minimum tillage II |
MT II |
The Cerrado was deforested in 1977, with subsequent cultivation of rice/soybean for 3 years under conventional tillage and, until the 1999/00 season, soybean/corn was cultivated in rotation under conventional tillage, disturbing the soil with heavy harrowing with discs of 32" every 3 years. In 2000/02, millet was cultivated, followed by gypsum application, two harrowings (32") and sowing of cotton. In 2002/03, gypsum was applied and soybean and corn were cultivated in the off-season. In 2003/04, cotton was sown on corn residues. In 2004/06, the soil was prepared with two harrowings (32"), and millet and cotton were sown in rotation. Then, gypsum was applied and the stumps were destroyed, combining a mechanical mowing with a harrowing to incorporate plant residues. In 2006/07, the soil was scarified until 0.30 m and millet and cotton were cultivated in rotation, with later destruction of the stumps. In 2007/08, millet and cotton were sown in rotation, with later destruction of the stumps. In 2008/09, limestone was applied in association with gypsum and soybean and corn were cultivated in the off-season. In 2009/10, cotton was sown on corn residues. Therefore, soil disturbance was more frequent in this tillage system than in the previous one, MT I. |
| Minimum tillage III |
MT III |
The Cerrado was deforested in 1976, with subsequent cultivation of rice/soybean for 3 years under conventional tillage and, until the 1999/00 season, soybean/corn was cultivated in rotation under conventional tillage, disturbing the soil with heavy harrowing with discs of 32" every 3 years. In 2000/04, cotton was cultivated, followed by corn, and limestone was applied before the 2001/02 season and incorporated with two harrowings (32"). Cotton stumps were destroyed combining mechanical mowing and harrowing to incorporate plant residues. In 2004/05, the soil was subjected to two harrowings (32"), subsoiled and sown with soybean followed by corn, with later gypsum application. In 2005/06, cotton was cultivated on corn residues. In 2006/10, there were crop rotations with soybean/corn, corn/cotton and soybean/cotton, respectively. Therefore, the soil was harrowed not only when cotton was cultivated, although a heavy harrow was used just at the end of its cycle to destroy the stumps. Thus, soil disturbance was more frequent in this system than in the previous ones (MT I and MT II), and millet was not cultivated. |
| Intensive pasture |
IP |
The Cerrado was deforested in 1978 and rice was cultivated from 1978 to 1980. In 1981, Brachiaria brizantha cv. Marandu was planted and weed control was manually performed every 2 years under intensive management with Nelore cattle for fattening, with mean capacity of 7-9 A.U. ha-1, without animal rotation. Since 1997, every 3 years, the soil has been chemically corrected with the dose of 1,5 Mg ha-1 of dolomitic limestone, plus a fertilization with 100 kg ha-1 of single superphosphate as top-dressing. Since 2003, between March and April, 10 tons of cotton hull have been applied. Gypsum was applied broadcast in 2008, in the dose of 500 kg ha-1. |
Carbon stocks of an Oxisol after thirty-eight years under different tillage systems
