Amanda Posselt Martins

Attributes of irrigated rice as affected by soil sodicity and potassic fertilizer application

Soils of the coastal plains of Rio Grande do Sul, Brazil, are affected by salinization, which can hamper the establishment and development of crops in general, including rice. The application of high doses of KCl may aggravate the crop damage, due to the high saline content of this fertilizer. This study aimed to evaluate the effect of K fertilizer management on some properties of rice plant, grown in soils with different sodicity levels, and determine which attribute is best related to yield. The field study was conducted in four Albaqualfs with exchangeable Na percentages of 5.6, 9.0, 21 and 32 %. The management of KCl fertilizer consisted of the application of 90 kg ha-1 K2O broadcast, 90 kg ha-1 K2O in the row and 45 kg ha-1 K2O in the row + 45 kg ha-1 K2O at panicle initiation (PI). Plant density, dry matter evolution, height, SPAD (Soil Plant Analysis Development value indicating relative chlorophyll contents) index, tiller mass, 1,000-grain weight, panicle length and grain yield were evaluated. The plant density was damaged by application of K fertilizer in the row, especially at full dose (90 kg ha-1), at three sodicity levels, resulting in loss in biomass accumulation in later stages, affecting the crop yield, even at the lowest level of soil sodicity (5.6 %). All properties were correlated with yield; the highest positive correlation was found with plant density and shoot dry matter at full flowering, and a negative correlation with panicle length.

Umidade do solo e fisiologia da soja afetados por estiagem em sistema de integração lavoura‑pecuária

The objective of this work was to evaluate the impact of grazing intensities after 11 years of an integrated crop‑livestock system, under no‑tillage, on soil moisture and soybean physiological parameters during a summer season affected by drought. The experiment was established in 2001 on a Rhodic Hapludox. Treatments consisted in the succession of soybean (summer) and a mixed pasture of black oat + Italian ryegrass (winter), under different beef‑cattle grazing intensities: intensive grazing, with 0.10‑m pasture height; moderate grazing, with 0.20‑m pasture height; and no grazing. During the soybean cycle, in the 2011/2012 crop season, rainfall was 40% of the climatological normal. The soil moisture was within the limits of available water both under moderate grazing and no grazing, at 0.00–0.50‑m soil depth, but, under intensive grazing, it was below the permanent wilting point, especially up to the grazing height of 0.20 m. Intensive grazing affected negatively the plant physiology parameters, reaching peaks of ‑2.5 MPa and +6°C for leaf water potential and leaf‑air temperature difference, respectively. Moderate grazing or the absence of grazing, during the winter season, results in similar physiological responses, contributing to soybean plant homeostasis.

Animal production and soil characteristics from integrated crop-livestock systems: toward sustainable intensification

Sustainable intensification of land-use practices has never been more important to ensure food security for a growing world population. When combined under thoughtful management, cover cropping and crop-livestock integration under no-till systems can benefit from unexpected synergies due to their unique features of plant-animal diversification and complex agroecosystem functions. Mimicking the nutrient coupling/decoupling processes of natural ecosystems by diversifying plant and animal components of no-till integrated crop-livestock operations is an essential feature of the design of agroecological systems that support self-regulating feedbacks and lend resilience while increasing productivity and ecosystem service provision. Focusing on grazing animals as drivers of agroecosystem change, we highlight the benefits of grazed cover crops in rotation with cash crops for primary and secondary production and for soil physical, chemical, and biological parameters. However, careful management of grazing intensity is imperative; overgrazing drives soil deterioration, while light to moderate grazing enhances overall system functioning and allows for the generation of emergent properties.