Nitrógeno total y sustancias húmicas en agregados del suelo cultivado con cebolla bajo siembra directa y preparación convencional

Abstract

Total nitrogen and humic substances in aggregates of soils with onion crops under no-tillage and conventional tillage systems Nitrógeno total y sustancias húmicas en agregados del suelo cultivado con cebolla bajo siembra directa y preparación convencional ABSTRACTThe objective of this study was to evaluate the soil total nitrogen (TN), and N contents in humic substances (HS) of the organic matter in aggregates of soils cultivated with onion under no-till system for horticulture (NTSH) and conventional tillage system (CTS), comparing with an area of forest. The evaluated treatments were natural vegetation (control), 100% black oats, 100% rye, 100% oilseed radish, intercrop of oilseed (14%) + rye (86%), intercrop of oilseed (14%) + black oats (86%), area under CTS of onion for ±37 years, and area with secondary forest for ±30 years. Five years after the NTSH implementation, undisturbed soil samples from the layers 0-5 cm, 5-10 cm, and 10-20 cm were collected; these samples presented aggregate sizes between 2.0 mm and 8.00 mm. The TN, and N contents of the HS were subdivided into fulvic acids (N-FA), humic acids (N-HA), and humin (N-HU) fractions. The change from CTS to NTSH increases the TN and N-HU contents in the 0-5 cm soil layer. The intercrop of oats and oilseed radish, used as soil plant cover species in NTSH, presented a greater increase in N-HU (0-20 cm) than the other treatments. Black oats, and natural Onion (Allium cepa L.) crops cover an area of approximately 60,000 ha annually in Brazil, producing approximately 1.6 million t of onion bulbs (IBGE, 2017). The southern region of the country produces 49% of the national production, where the state of Santa Catarina (SC) stands out as the largest national producer since 1990, with a profitable production that has becoming more sustainable due to organic production studies (ACATE, 2014).Soil conventional tillage system (CTS) is the most used system for onion crops in SC, comprising frequent turning of the soil (plowing, harrowing, subsoiling or scarification) in the preparation of the soil of the planting bed (Menezes et al., 2013). This soil preparation increases the occurrence of erosive processes and changes edaphic attributes, decreasing nutrient availability to plants and soil organic matter content (Loss et al., 2015). CTS is an important system for food, fiber and energy production, however, it impacts the soil; thus, the search for soil management and conservation practices has been a constant challenge. No-till system for horticulture (NTSH) has stood out as a promising alternative for onion crops (Menezes et al., 2013). Soil turning in NTSH is done only in the planting line, and cover plants are used for the production and maintenance of plant residues on the soil. This practice maintains or increases the vegetation presented a greater increased in N-HA, and N-FA contents, respectively, in the 10-20 cm layer, than the other treatments in NTSH and CTS. CTS with millet as soil plant cover presented a greater increase in N-FA (0-20 cm) contents tha...

Carbon increase and soil physical improvement in an onion no-tillage system

“…The CT management showed lower MAC content, which can be explained by intense soil disturbance that consumes soil organic matter (SOM). The difference between the productive areas and the forest area lies in the composition and quality of the residues added to the soil, and the area of native vegetation is considered a reference to analyze the effects that the change in soil use and management can bring on SOM dynamics (Santos et al, 2018).…”

Soil Carbon, Glomalin, And Aggregation in Onion Crop Under No-Tillage with Cover Crops or Conventional Tillage Systems for Eight Years

“…Cover crop species improve soil physical and chemical attributes in onion fields (Loss et al, 2017;Comin et al, 2018a;Santos et al, 2018;Ferreira et al, 2018) as well as soil biological properties (Silva et al, 2014). They also lead to lower weed emergence, affecting onion yield and quality (Vilanova et al, 2014;Oliveira et al, 2016;Comin et al, 2018b;Souza et al, 2018).…”

“…Plant growth and decomposition of their residues on soils affect soil water infiltration, prevents erosive processes, lowers thermal amplitude, and increases nutrient cycling, organic matter (SOM), cation exchange capacity (CEC), and the sum of bases (Loss et al, 2017;Santos et al, 2018, Upton et al, 2019. Weed competition also tends to be lower because of plant residues' physical barrier (Comin et al, 2018a;Souza et al, 2018).…”