Can C-budget of natural capital be restored through conservation agriculture in a tropical and subtropical environment?

Conservation agriculture through no-till based on cropping systems with high biomass-C input, is a strategy to restoring the carbon (C) lost from natural capital by conversion to agricultural land. We hypothesize that cropping systems based on quantity, diversity and frequency of biomass-C input above soil C dynamic equilibrium level can recover the natural capital. The objectives of this study were to: i) assess the C-budget of land use change for two contrasting climatic environments, ii) estimate the C turnover time of the natural capital through no-till cropping systems, and iii) determine the C pathway since soil under native vegetation to no-till cropping systems. In a subtropical and tropical environment, three types of land use were used: a) undisturbed soil under native vegetation as the reference of pristine level; b) degraded soil through continuous tillage; and c) soil under continuous no-till cropping system with high biomass-C input. At the subtropical environment, the soil under continuous tillage caused loss of 25.4 Mg C ha-1 in the 0-40 cm layer over 29 years. Of this, 17 Mg C ha-1 was transferred into the 40-100 cm layers, resulting in the net negative C balance for 0-100 cm layer of 8.4 Mg C ha-1 with an environmental cost of USD 1968 ha-1. The 0.59 Mg C ha-1 yr-1 sequestration rate by no-till cropping system promote the C turnover time (soil and vegetation) of 77 years. For tropical environment, the soil C losses reached 27.0 Mg C ha-1 in the 0-100 cm layer over 8 years, with the environmental cost of USD 6155 ha-1, and the natural capital turnover time through C sequestration rate of 2.15 Mg C ha-1 yr-1 was 49 years. The results indicated that the particulate organic C and mineral associate organic C fractions are the indicators of losses and restoration of C and leading C pathway to recover natural capital through no-till cropping systems.

C-offset and crop energy efficiency increase due industrial poultry waste use in long-term no-till soil minimizing environmental pollution.

Brazil is one of the major global poultry producers, and the organic waste generated by the chicken slaughterhouses can potentially be used as a biofertilizer in agriculture. This study was designed to test the hypothesis that continuous use of biofertilizer to the crops, substituting the use of mineral fertilizer promote C-offset for the soil and generate crop energy efficiency for the production system. Thus, the objectives of this study were to evaluate the effects of biofertilizer use alone or in combination with mineral fertilizer on soil organic carbon (SOC) stock, carbon dioxide (CO2) mitigation, C-offset, crop energy efficiency and productivity, and alleviation of environmental pollution. The experiment was established in southern Brazil on a soil under 15 years of continuous no-till (NT). Experimental treatments were as follows: i) Control with no fertilizer application, ii) 100% use of industrial mineral fertilizer (Min-F); iii) 100% use of organic waste originated from poultry slaughterhouses and hereinafter designated biofertilizer (Bio-F), and iv) Mixed fertilizer equivalent to the use of 50% mineral fertilizer + 50% of biofertilizer (Mix-F). Effects of experimental treatments were assessed for the crop sequence based on bean (Phaseolus vulgaris), soybean (Glycine max) and corn (Zea mays) in the summer and wheat (Triticum aestivum) and black oat (Avena strigosaSchreb) in the winter composing two crops per year, as follow: bean/wheat-soybean/black oat-corn/wheat-soybean/black oat-corn/wheat-bean. The continuous use of Bio-F treatment significantly increased the index of crop energy efficiency. It was higher than that of control, and increased it by 25.4 Mg CO2eq ha-1 over that of Min-F treatment because of higher inputs of crop biomass-C into the system. Further, continuous use of Bio-F resulted in a significantly higher CO2eq stock and offset than those for Min-F treatment. A positive relationship between the C-offset and the crop energy efficiency (R2 = 0.71, p < 0.001) indicated that the increase of C-offset was associated with the increase of energy balance and the amount of SOC sequestered. The higher energy efficiency and C-offset by application of Bio-F indicated that the practice of crop bio fertilization with poultry slaughterhouse waste is a viable alternative for recycling and minimizing the environmental impacts.

Residues Decomposition in Crop Rotations under No-till System

Abstract The effectiveness soil cover in no-till is relating to quantity and quality of the phytomass produced by crops in rotation and, its persistence over the soil depends on residues decomposition. The objective of this study was to evaluate the phytomass production, decomposition rate and the half-life of crops in rotation at the Subtropical region, Brazil. The study was carried out at the Agronomic Institute of the Paraná (IAPAR), in Ponta Grossa, Parana State, Brazil. The experimental design was randomized blocks, with six treatments and four replicates. Winter cash crops and cover crops, single and in consortium, were evaluated in the year 2014 (wheat, black oats + hairy vetch + rye, black oats + ryegrass and black oats + blue lupine), in 2015 (canola, black oats, and black oats + hairy vetch + forage turnip) and in 2016 (barley, triticale, and triticale + black oats + rye). The phytomass was evaluating by collect three subsamples of 0.25 m2 per plot. For decomposition rate and the half-life of the crop residues, litter bags (LBs) methodology was used. A mathematical model (Q=Q0exp-kt) was used to represent the crop residues decomposition and the half-life of crop residues were obtained by the equation t1/2 = (ln2)/k. Poaceae consortia, single Poaceae and canola presented higher phytomass production when compared to Poaceae-Fabaceae consortia. The half-life for Poaceae-Fabaceae corsortia was shorter than single Poaceae.

Soil Carbon and Structural Quality in Crop Rotations under No-tillage System

Abstract The no-tillage system associated with crops rotation affects the dynamics of soil organic matter, influencing the formation, reorganization and stabilization of aggregates and the carbon content (C) into soil aggregates. The aim of this study was to evaluate the effect of crop rotations under no-tillage system on C content and soil aggregation. The experiment was conducted at the Paraná Agronomic Institute in Ponta Grossa, PR, Brazil. The treatments consisted of six crop rotations, in a 3-year cycle, arranged in a randomized block design with four replications. Soil samples were collected at layers of 0-5, 5-10 and 10-20 cm. The aggregate classification was determined by the wet sieving methodology, and the Weighted Mean Diameter (WMD), Geometric Mean Diameter (GMD) and Aggregate Stability Index (ASI) were calculated. The C content in the aggregates was determined by wet oxidation. The results were submitted to analysis of variance and Tukey test at 5% probability. There was no difference among crop rotations for aggregate classes and aggregation indexes, but were higher in surface, decreasing in depth. The carbon content in the aggregates did not differ among crop rotations, but presented stratification in the soil profile, decreasing in depth. The cycle of three years with crop rotation was insufficient to express possible changes in soil C content and aggregation.

Relação de estratificação como indicador do sequestro de carbono em macroagregados de Latossolo sob plantio direto / Stratification ratio as soil carbon sequestration indicator in macroaggregates of Oxisol under no-tillage

A redução no conteúdo de carbono (C) nas camadas mais profundas do solo indica a estratificação entre a camada superficial e as subsuperficiais, devido à adição contínua de C pelos resíduos culturais na superfície. O objetivo deste trabalho foi avaliar a variação (∆) da relação de estratificação (RE) de carbono como indicadora do sequestro de C total e particulado em macroagregados de dois Latossolos de classes texturais diferentes, manejados em sistema plantio direto. Os ensaios foram desenvolvidos em delineamento inteiramente casualizado com doze repetições. Os fatores analisados foram: (a) dois solos (Latossolo Vermelho Distrófico típico com classe textural franco-argilo-arenosa e Latossolo Vermelho Distrófico típico com classe textural franco-argilosa); (b) duas camadas de amostragem (0-5 e 5-20cm de profundidade); (c) duas épocas de amostragem (E1-outubro de 2007; E2-setembro de 2008). Observou-se relação linear e significativa entre o delta RE com a taxa de sequestro de C total em macroagregados no Latossolo Vermelho com classe textural franco argilo arenosa (R²=0,78**) e franco argilosa (R²=0,81**), indicando ter havido sequestro de C e confirmando ser este um indicador sensível da taxa de sequestro de C no solo em macroagregados.

The decrease in soil organic carbon (SOC) content in deeper layers indicates the occurrence of stratification between the surface layer and subsurface layer of soil due to continuous C addition by crop residues. The objective was to evaluate the change (delta) of stratification (RE) of carbon (C) as an indicator of C sequestration and soil total and particulate soil in macroaggregates of two soils (Typic Hapludox) with different textures, managed in no-tillage system. The tests were developed in completely randomized design twelve repetitions.Analyzed factors were: (a) two soils: Oxisol with medium texture and Oxisol with clay texture, (b) sampling depth: 0-5 and 5-20cm, (c) two sampling times (October 2007-T1, September 2008-T2). The results were submitted to variance analysis by program SISVAR 5.3, using the Tukey test at 5% significance. There was a significant linear relationship between the ∆ RE and carbon sequestration rate total macroaggregates Oxisol with medium texture (R²=0.78**) and Oxisol with clay texture (R²=0.81**) indicating that there was C sequestration confirming to be a sensitive indicator of the rate of C sequestration in soil macroaggregates.