ABSTRACT The purpose of this study was to conduct a cultural energy analyses of beef cattle receiving different levels of concentrate. Data were obtained via questionnaire from 100 beef cattle farms selected by a stratified, random sampling method. Beef cattle farms were divided into three groups according to concentrate level and were analyzed. Accordingly concentrate levels were assigned as low (< 55% 35 farms), intermediate (55% to 65%, 34 farms) and high (> 65%, 31 farms). Cultural energy used for feed for treatments was derived from their corresponding lot feed consumption and their corresponding values from the literature. Transportation energy was also included in the analysis. Since the objective of the study was to evaluate cultural energy analysis of the feeding systems, energy that the calves had deposited in their muscle and fat tissue when they were bought was deducted from carcass energy. Total cultural energy expended was highest for cattle receiving a low level of concentrate (p < 0.05). Feed energy constituted more than half of the total cultural energy and was highest for cattle receiving a low level of concentrate (p < 0.05). Energy expended per kg live weight did not differ among groups by concentrate level (p > 0.05). Cultural energy per Mcal protein energy was highest for cattle receiving a low level of concentrate and was lowest for cattle receiving an intermediate level of concentrate (p < 0.05). Cultural energy for cattle receiving a high level of concentrate was intermediate and thus did not differ significantly from the other groups (p > 0.05). Efficiency, defined as Mcal input/Mcal output, was better for cattle receiving an intermediate level of concentrate and was worse for cattle receiving a low level of concentrate (p < 0.05). Efficiency for cattle receiving a high level of concentrate was intermediate and thus did not differ significently from the other groups (p > 0.05). Results showed that efficiency does not linearly increase as concentrate level increases; thus, in order to be more sustainable, a strategy of decreasing concentrate level without interfering with cattle performance should be considered.
This article sketches a brief panorama of the advances and challenges involved in the implementation of the agroecological approach in Brazilian institutions. It begins with an account of the struggles of rural social movements working at the deepest grassroots level of the country's “agroecological field.” The processes that led to the creation and development of the National Agroecology Alliance (ANA) and the Brazilian Agroecology Association (ABA-Agroecologia) are presented as a key part of the construction now under way. Taking as a baseline the evolutions in the internalization of agroecology in official teaching, research, and rural extension services, the article identifies some of the powerful practical, theoretical, and politico-ideological obstacles preventing the rupture with the paradigm of modernization on the part of state institutions.
Monsampolo Organic VEgetable (MOVE) long-term field experiment produced a comparison between organic and a conventionally managed agroecosystem for vegetable production in Central Italy. The study was based on a four-year crop rotation involving six main crops: tomato, melon, fennel, lettuce, cauliflower, and bean. The experiment started in 2001. The agronomic performance and environmental sustainability of the two different management systems were assessed over a three-year period (2007–2010), comparing a) the yield and produce quality; b) cultivar adaptability to organic farming conditions; c) soil quality; and d) potential risk of soil nitrogen leaching. The organic and conventional four-years rotation systems yielded similarly and most of the crops showed no significant differences in produce quality. The study also indicates that comparisons among cultivars to be used in organic farming should be carried out on such experimental field sites where organic farming management had been in place for the long term. Our study demonstrated that soil organic C and total N increased, respectively, of 37% and 22% in the organically managed vegetable production system as compared to the conventional one. The risks of soil nitrate leaching were higher in autumn/winter conventionally managed crops as compared to the organic ones.
The contribution of cover crop roots to soil dynamics is poorly understood, in part because little information is available on the distribution, depth, chemical compositional changes over time, and nutrient mineralization rates of typical cover crop roots. A study was conducted to investigate the role of cover crop roots in a long-term trial on the effects of cover crop species and seasonal placement on soil properties in a vegetable rotation. Root length density (RLD), chemical composition, and nitrogen mineralization during incubation were measured in roots of red clover (Trifolium pratense L.) and winter rye (Secale cereale L.) of varying ages. Nearly 50% of the fine root RLD was measured in the top 5 cm for all roots, with no significant differences between species and ages. Lignin concentration in red clover roots increased nearly four-fold as they aged from 4 to 24 months, while N concentration were 22% lower in the older roots. N concentration decreased by 50% in rye roots from 0 to 9 months, leading to doubling of C:N. During incubation, net N mineralization was greater from 24 month-old red clover roots than 12-month roots, while winter rye roots showed net N immobilization over the incubation period.
Organic grain production is not common to eastern Washington, but offers attractive market opportunities if systems can be developed that are compatible with regional production constraints. Erodible soils make tillage-intensive systems unsustainable, and there are limited alternative fertility options. Given these constraints, the objective of this study was to evaluate nine cropping systems during the transition to organic grain production under reduced tillage and relying on legumes as the primary source of crop nitrogen. The experimental transition systems ranged in the degree in which legume grain crops or legume green manures/forages were present in the rotation. We found that spring pea grown for grain to be a poor choice for organic production due to the susceptibility of this crop to insect pests and weeds, which generally resulted in crop failure. Likewise, bell bean was poorly suited as a legume green manure crop due to its low productivity in our region. In contrast, alfalfa and winter pea-based systems achieved the best legume biomass production, weed suppression, and crop yields in the subsequent crops. Winter wheat substantially out-yielded spring wheat, but the yields of both of these crops were well below the yield potential typically achieved under conventional production. Competition from annual weeds, such as wild oat and prickly lettuce, and the perennial weed field bindweed was difficult to manage under the reduced tillage regimes employed in this study.
