First-order decay models to describe soil C-CO2 Loss after rotary tillage

To further understand the impact of tillage on CO2 emission, the applicability of two conceptual models was tested, which describe the CO2 emission after tillage as a function of the non-tilled emission plus a correction due to the tillage disturbance. Models assume that C in readily decomposable organic matter follows a first-order reaction kinetics equation as: dCsoil (t) / dt = -k Csoil (t), and that soil C-CO2 emission is proportional to the C decay rate in soil, where Csoil(t) is the available labile soil C (g m-2) at any time (t) and k is the decay constant (time-1). Two possible assumptions were tested to determine the tilled (F T) fluxes: the decay constants (k) of labile soil C before and after tillage are different (Model 1) or not (Model 2). Accordingly, C flux relationships between non-tilled (F NT) and tilled (F T) conditions are given by: F T = F NT + a1 e-a2t (model 1) and F T = a3 F NT e-a4t (model 2), where t is time after tillage. Predicted and observed CO2 fluxes presented good agreement based on the coefficient of determination (R² = 0.91). Model comparison revealed a slightly improved statistical fit of model 2, where all C pools are assigned with the same k constant. Rotary speed was related to increases in the amount of labile C available and to changes of the mean resident labile C pool available after tillage. This approach allows describing the temporal variability of tillage-induced emissions by a simple analytical function, including non-tilled emission plus an exponential term modulated by tillage and environmentally dependent parameters.Para entendimento do impacto do preparo do solo sobre as emissões de CO2 desenvolvemos e aplicamos dois modelos conceituais que são capazes de prever a emissão de CO2 do solo após seu preparo em função da emissão da parcela sem distúrbio, acrescida de uma correção devido ao preparo. Os modelos assumem que o carbono presente na matéria orgânica lábil segue uma cinética de decaimento de primeira ordem, dada pela seguinte equação: dCsoil (t) / dt = -k Csoil (t), e que a emissão de C-CO2 é proporcional a taxa de decaimento do C no solo, onde Csolo(t) é a quantidade de carbono lábil disponível no tempo (t) e k é a constante de decaimento (tempo-1). Duas suposições foram testadas para determinação das emissões após o preparo do solo (Fp): a constante de decaimento do carbono lábil do solo (k) antes e após o preparo é igual (Modelo 1) ou desigual (Modelo 2). Conseqüentemente, a relação entre os fluxos de C das parcelas sem distúrbio (F SD) e onde o preparo do solo foi conduzido (F P) são dadas por: F P = F SD + a1 e-a2t (modelo 1) e F P = a3 F SD e-a4t (modelo 2), onde t é o tempo após o preparo. Fluxos de CO2 previstos e observados relevam um bom ajuste dos resultados com coeficiente de determinação (R²) tão alto quanto 0,91. O modelo 2 produz um ajuste ligeiramente superior quando comparado com o outro modelo. A velocidade das pás da enxada rotativa foi relacionada a um aumento na quantidade de carbono lábil e nas modificações do tempo de residência médio do carbono lábil do solo após preparo. A vantagem desta metodologia é que a variabilidade temporal das emissões induzidas pelo preparo do solo pode ser descrita a partir de uma função analítica simples, que inclui a emissão da parcela sem distúrbio e um termo exponencial modulado por parâmetros dependentes do preparo e de condições ambientais onde o experimento foi conduzido

Vibration Effects on the Performance of a Single-Shank Subsoiler

Rosana G. Moreira, Editor-in-Chief; Texas A&M UniversityThis is a paper from International Commission of Agricultural Engineering (CIGR, Commission Internationale du Genie Rural) E-Journal Volume 9 (2007): Vibration Effects on the Performance of a Single-Shank Subsoiler. Manuscript PM 07 018. Vol. IX. September, 2007

Automatic non-destructive quality inspection system for oil palm fruits

In this research a non-destructive, rapid and cost effective examination machine for the estimation of the ripeness fraction, oil content and free fatty acid level in oil palm fresh fruits bunch was developed. The automatic machine-vision based in- spection system provided consistency, rapid estimation and accep- table accuracy results in non-dest ructive manner. Fresh fruits bunch samples from Tenera cultivar (7 to 20 years trees) were taken from Cimulang plantation, Bogor, Indonesia. Two statistical analysis methods were used: a forward stepwise multiple linear regression analysis and a multilayer-perceptron artificial neural network analysis. The best prediction of ripeness and oil content models were obtained using the latter method, while the best free fatty acid prediction model was developed by the first method. The models were then employed in the machine-vision inspection systems of the machine. The system best prediction accuracy of ripeness, oil content and free fatty acid models was 93.5, 96.41, and 89.32%, with standard error of prediction being 0.065, 0.044 and 0.068, respectively. The system was tested through a series of field tests, and successfully examined more than 12 t of fruits bunch per hour, without causing damage

Automatic Non-destructive Quality Inspection System for Oil Palm Fruits

In this research a non-destructive, rapid and cost effective examination machine for the estimation of the ripeness fraction, oil content and free fatty acid level in oil palm fresh fruits bunch was developed. The automatic machine-vision based in- spection system provided consistency, rapid estimation and accep- table accuracy results in non-dest ructive manner. Fresh fruits bunch samples from Tenera cultivar (7 to 20 years trees) were taken from Cimulang plantation, Bogor, Indonesia. Two statistical analysis methods were used: a forward stepwise multiple linear regression analysis and a multilayer-perceptron artificial neural network analysis. The best prediction of ripeness and oil content models were obtained using the latter method, while the best free fatty acid prediction model was developed by the first method. The models were then employed in the machine-vision inspection systems of the machine. The system best prediction accuracy of ripeness, oil content and free fatty acid models was 93.5, 96.41, and 89.32%, with standard error of prediction being 0.065, 0.044 and 0.068, respectively. The system was tested through a series of field tests, and successfully examined more than 12 t of fruits bunch per hour, without causing damage

Hlađenje objekata zaštićenog prostora u vlažnim tropskim uslovima - problemi i rešenja

The development of a greenhouse suitable for protected cultivation in the humid tropics is still far from being realized. Reducing the heat load without increasing humidity inside the greenhouse, pest exclusion without heavy reliance on chemicals and monitoring plant response to changes in the microenvironment are the main challenges. As such the development of a strategy that allows for rational use of resources for high quality plant production while ensuring maximum protection and sustainability of the environment is still being sought. The progress made in developing an adapted greenhouse that encourages biological pest control and simultaneously offers an optimum microclimate is discussed in the concept of integrated plant production in the humid tropics.Konačno rešenje objekta zaštićenog prostora pogodnog za gajenje useva u vlažnim tropskim uslovima, još uvak nije nađeno. Glavni problemi su kako sniziti temperaturu u objektima a pritom ne povećati relativnu vlažnost vazduha i kako eliminisati insekte bez povećane upotrebe hemijskih zaštitnih sredstava. U svetu se sve češće predlažu nove strategije održive poljoprivrede čijom bi se primenom smanjila upotreba hemijskih zaštitnih sredstava i tako dikerktno uticalo na ekološki opravdaniju poljoprivrednu proizvodnju ne umanjujući time kvalitet na ovaj način dobijenih poljoprivrednih proizvoda. U radu se analizira mogućnost razvoja tehnološko-tehničkog sistema objekta zaštićenog prostora u kome bi bila moguća biološka kontrola insekata uz održanje optimalnih mikroklimatskih uslova