Fernando Antônio Macena da Silva

Conservation agriculture cropping systems in temperate and tropical conditions, performances and impacts. A review

Nowadays, in a context of climate change, economical uncertainties and social pressure to mitigate agriculture externalities, farmers have to adopt new cropping systems to achieve a sustainable and cost-effective grain production. Conservation agriculture consists of a range of cropping systems based on a combination of three main principles: (1) soil tillage reduction, (2) soil protection by organic residues and (3) diversification in crop rotation. Conservation agriculture has been promoted as a way to reduce production costs, soil erosion and soil fertility degradation under both tropical and temperate conditions. Conservation agriculture-based cropping systems have diffused widely under Brazilian large-scale farms’ conditions and more recently in Europe in the context of medium-size mechanized farms. Their diffusion, however, is still limited under small-scale non-mechanized farms’ conditions of tropical countries. To assess the advantages and limits of such new cropping systems, this article compares experiences with conservation agriculture from the tropical Cerrado region of Brazil and from temperate conditions of Europe. It focusses on agronomic performances, environmental impacts and economical results. Conservation agriculture systems appear to be interesting options to achieve sustainable and intensive crop production under different agroecological environments because they use efficiently available resources and maintain soil fertility. However, this mostly results from the permanent presence of an organic mulch on the soil surface and the incorporation of cover crops in the rotations. Such modifications require a significant reorganization of the production process at farm level, and when facing technical or socioeconomic constraints, most farmers usually opt for applying only partially the three main principles of conservation agriculture. Investigating more fully the consequences of such partial implementation of conservation agriculture principles on its actual efficiency and assessing the most efficient participatory approaches needed to adapt conservation agriculture principles to local conditions and farming systems are top priorities for future research.

Climatic risk zoning for corn and palisade grass (Brachiaria brizantha cv: Marandu) cultivated in integrated crop-livestock systems in São Paulo state, Brazil

Climatic risk zoning allows the identification of areas of low risk of reduced crop productivity due to climatic events. In Brazil, losses to agriculture due to climate are mainly caused by drought. The objective of this research was to determine areas of low climatic risk for corn and palisade grass cultivated in integrated crop-livestock systems in Sao Paulo state. Corn varieties characterized by a 120-day growing cycle and soil with three different water holding capacities (sandy, medium and clayey soils) were considered. A daily water balance model was used to simulate planting dates between September and December. The water requirement satisfaction index (WRSI) was calculated for critical phenological phases of both cultures (germination, emergence and tillering of palisade grass and flowering and grain filling of corn). The WRSI values, calculated for a minimum frequency of 80%, were located spatially using the SPRING v. 5.1 geographic information system and the most favorable periods for sowing in different areas were determined. The results showed that there are areas of low climatic risk for cultivation of corn and palisade grass in integrated crop-livestock production systems in Sao Paulo state. Although climatic risk in these areas also depends on soil type, the most favorable period for planting is between October and November.