Dry Matter Decomposition of Cover Crops in a No-Tillage Cotton System

Abstract

-No-tillage cotton systems require soil coverage with cover crop residue for a longer time due to the late cycle of cotton. However, decomposition rates may vary between cover crops, and the adjustment of models to describe it is critical to no-tillage cotton management. Two non-linear regression models, exponential (EM) and Michaelis-Menten (MM), were adjusted to dry matter decomposition of cover crops in a cotton no-tillage system, in Brazil. Three field trials were performed in 2012 for the cover crops Urochloa ruziziensis (brachiaria), Pennisetum glaucum (pearl millet), and Cajanus cajan (pigeon pea). Samples of cover crop were collected at 20, 50, 70, 110, 140, and 170 days after sowing upland cotton to measure dry matter decomposition. MM showed better adjustment than EM for all cover crops. The estimations of half-life parameters were different between the cover crops, suggesting that each cover crop has its own rate of decomposition. For pearl millet, brachiaria, and pigeon pea, the half-life estimation by exponential model was over the MM in 9, 12, and 12 days. RESUMO -Para a semeadura direta é preciso adequada quantidade de palha sobre o solo, e devido ao longo ciclo do algodoeiro, sua persistência deve ser alta. Entretanto, como a decomposição dos resíduos vegetais ao longo do tempo pode variar entre as plantas de cobertura, o ajuste de modelos que melhor a descreva é essencial. Dois modelos de regressão não-linear, exponencial (ME) e Michaelis-Menten (MM), foram ajustados à decomposição de matéria seca de plantas de cobertura no sistema de semeadura direta do algodoeiro, em condições do Cerrado goiano. Três experimentos foram instalados no ano de 2012, cada um consistido de uma espécie de planta de cobertura, sendo Urochloa ruziziensis (braquiária ruziziensis), Pennisetum glaucum (milheto) e Cajanus cajan (guandu). Em cada ensaio, procedeu-se a amostragem da palha da planta de cobertura aos 20, 50, 70, 110, 140 e 170 dias após a semeadura do algodoeiro, para determinação da matéria seca remanescente. Para as três plantas de cobertura o modelo MM apresentou melhor ajuste que o ME. As estimativas dos tempos de meia-vida das palhadas via MM diferiram entre as plantas de cobertura, indicando que cada uma possui velocidade de decomposição específica. Para o milheto, o guandu e a braquiária, as estimativas de tempo de meia-vida pelo ME foram superiores às do MM em 9, 12 e 12 dias, respectivamente.Palavras-chave: Modelo exponencial. Michaelis-Menten. Gossypium hirsutum. Plantio direto.

Do cover crops improve the productivity and industrial quality of upland rice?

“…Most species cultivated as cover crops are either grasses or leguminous plants. Millet ( Pennisetum glaucum ) is one of the most used grasses in the Brazilian Cerrado (Ferreira Junior et al., ) because of its high straw yield (Pacheco et al., , ; Silva Filho, Borin, & Ferreira, ), with an average of 10 t ha −1 (Wutke, Calegari, & Wildner, ), and its high C/N ratio. These attributes promote greater soil protection (Silva Filho et al., ) and increased nutrient cycling (Pacheco et al., , ), even under water deficit conditions (Pacheco et al., ).…”

“…Millet ( Pennisetum glaucum ) is one of the most used grasses in the Brazilian Cerrado (Ferreira Junior et al., ) because of its high straw yield (Pacheco et al., , ; Silva Filho, Borin, & Ferreira, ), with an average of 10 t ha −1 (Wutke, Calegari, & Wildner, ), and its high C/N ratio. These attributes promote greater soil protection (Silva Filho et al., ) and increased nutrient cycling (Pacheco et al., , ), even under water deficit conditions (Pacheco et al., ). The pigeonpea ( Cajanus cajan ), a legume, is adapted to the Cerrado and has a high straw yield (Silva Filho et al., ) of 5–18 t ha −1 (Wutke et al., ) because it tolerates high temperatures and water deficits; in addition, pigeonpea cultivation also increases the amount of N in the soil, between 41–280 kg ha −1 yr −1 (Wutke et al., ), through biological fixation (Silva Filho et al., ).…”

“…These attributes promote greater soil protection (Silva Filho et al., ) and increased nutrient cycling (Pacheco et al., , ), even under water deficit conditions (Pacheco et al., ). The pigeonpea ( Cajanus cajan ), a legume, is adapted to the Cerrado and has a high straw yield (Silva Filho et al., ) of 5–18 t ha −1 (Wutke et al., ) because it tolerates high temperatures and water deficits; in addition, pigeonpea cultivation also increases the amount of N in the soil, between 41–280 kg ha −1 yr −1 (Wutke et al., ), through biological fixation (Silva Filho et al., ). Sunn hemp ( Crotalaria juncea ), another legume adapted to the Cerrado, exhibits rapid growth, has the potential to produce from 4–15 t ha −1 of straw, and fix between 150–165 kg ha −1 of N per year (Wutke et al., ).…”

“…These attributes promote greater soil protection (Silva Filho et al, 2018) and increased nutrient cycling (Pacheco et al, 2011b(Pacheco et al, , 2013, even under water deficit conditions (Pacheco et al, 2011b). The pigeonpea (Cajanus cajan), a legume, is adapted to the Cerrado and has a high straw yield (Silva Filho et al, 2018) of 5-18 t ha −1 (Wutke et al, 2014) because it tolerates high temperatures and water deficits; in addition, pigeonpea cultivation also increases the amount of N Core Ideas • Cover crops cultivated in winter or spring provide additional straw and nutrients to the system. • Sunn hemp straw offered adequate N, coordinated with the highest demand phase of rice.…”

“…in the soil, between 41-280 kg ha −1 yr −1 (Wutke et al, 2014), through biological fixation (Silva Filho et al, 2018). Sunn hemp (Crotalaria juncea), another legume adapted to the Cerrado, exhibits rapid growth, has the potential to produce from 4-15 t ha −1 of straw, and fix between 150-165 kg ha −1 of N per year (Wutke et al, 2014).…”