Yield Intensification Research Articles

Benchmarking Yield for Sustainable Intensification of Oil Palm Production in Indonesia Using PALMSIM

The physiological oil palm growth model PALMSIM can be used to estimate yield ceilings that provide benchmarks for sustainable intensification of oil palm production, either by expansion of cultivation to degraded sites or by increasing production from areas under cultivation. This is demonstrated using two case studies. In the first case study, PALMSIM estimates of water-limited yield for Kalimantan was overlaid onto a recently published map showing degraded sites potentially suitable for oil palm cultivation. A large proportion (35.6%; or 115,300 km2) of the identified areas fell into the potential productivity range of 35 to 40 tonnes FFB per hectare. In the second case study, PALMSIM was used to estimate potential yield for six plantation sites in Indonesia where best management practices (BMP) were assessed for yield intensification by the International Plant Nutrition Institute (IPNI) Southeast Asia Program (SEAP) and its collaborating plantation partners. Potential yields are generally higher in Sumatra than in Kalimantan due to higher solar radiation. Water deficit was a problem at two sites. The gap between water-limited yield and actual yield differs from location to location, and therefore requires a site-specific analysis. In these two case studies, the scope for sustainable intensification at regional and at plantation level was explored in a quantitative manner - a novel approach to oil palm production. Keywords: PALMSIM, oil palm intensification, yield benchmarking.

COMPRESSING BEHAVIOR AND TEXTURE EVALUATION FOR POTATOES PRETREATED BY PULSED ELECTRIC FIELD

ABSTRACT The objective of this study was to investigate the effects of pulsed electric field (PEF) treatment on compressing behavior and texture of potatoes. Textural data reveal that PEF treatment can cause enlargement of pressure for the same level of deformation. The fracture pressures Pc were approximately the same for both untreated and PEF‐treated specimens, Pc ≈ 4.5 ± 0.4 MPa. The maximal pressure Pm, at which the time of the pressure‐induced rupture of intact cells should be of the same order of magnitude as the time of fluid expression from damaged cells, was estimated as Pm ≈ 6 MPa. For a small pressure (P = 1 MPa) to obtain a similar deformation (ε = 0.15) requires pressing time t ≈ 3.5 h for untreated tissue and t ≈ 70 s for PEF‐treated tissue. Measured electrical conductivity was practically constant and exhibited no noticeable time dependence during constant pressure stage in untreated samples, while the conductivity of PEF‐treated specimens decreases in the course of pressing.PRACTICAL APPLICATIONSSolid–liquid expression is widely used in the food industry for the extraction of fruit and vegetables. Efficiency of this process can be increased by different pretreatment methods. Pulsed electric field (PEF) has been shown to be good for juice yield intensification and for improving the product quality in juice production. It is of great interest for process purposes to study texture proprieties of PEF‐treated and untreated tissues, because texture is one of the most important quality attributes of food products. This work also gives new information about the mechanism of the PEF‐induced damage and expression from tissues. The obtained results may be helpful for development of new engineering concepts based on PEF‐enhanced extraction at comparatively low pressures and moderate time of processing.

Agricultural land use and economic growth: environmental implications of the Kuznets curve

The expansion of agricultural land use has been associated with the loss of amenities, such as biological diversity, ecosystem services, and aesthetic values. Here, the determinants of agricultural land use are examined, drawing on panel data from 121 countries over the period 1965–1987. The analysis finds that an inverted U curve (or environmental Kuznets curve) describes the relationship of agricultural land use and per capita income. Turning points in cropland use at $1540 in per capita income and at $957 for pastureland use are identified, after which further economic development is correlated with a gradual retirement of agricultural land. The pattern varies somewhat by geographic region. Also, crop yields are found to be negatively correlated with agricultural land use; population density and ownership security are positively associated with agricultural land use; and trade variables show no clear pattern. These results suggest an dilemma. Although economic growth and yield intensification can lead to a reduction in agricultural land use, these forces may also increase degradation within the agricultural sector.

Rigid-plastic and damage behavior in metal forming: Part II—model prediction

Abstract Local sites of material damage by yield intensification and fracture are predicted for a rigid punch deforming a metal sheet in small steps. A modified theory of rigid-plasticity developed in Part I is used in combination with the volume energy density criterion. The condition of perfect elastic rigidity is relaxed in addition to the inclusion of material compressibility and dilatational energy. Compatibility of physical description, numerical computation and damage prediction is emphasized for defining the size of the smallest resolvable detail in an account of the workpiece's structure integrity and configuration tolerance. Computer models are shown to be forgiving when applied to describe global behavior such as punch force/displacement relation, workpiece configuration, etc., but large differences are reflected in the local stress/strain fields and material damage details. Sixteen Gaussian points are required in each of the twelve-node isoparametric elements to achieve sufficient accuracy for determining the maxima and minima of the volume energy density function. Their local and global values are identified with the potential failure sites and stability of the material degradation process. The ability of the workpiece to absorb plastic energy is shown to decrease with increase intensification of yielding and localized necking. A stage would be reached where further energy dissipation takes place in the form of fracture. Progressive cracking is found to be more unstable at the fixed end in contrast to the region under the punch with severe through-thickness necking. These effects are accessed quantitatively by an instability index parameter through which loading rate, workpiece geometry and material type could be optimized as a combination. Predicted fracture path in the necked region of the workpiece is reminiscent to that observed in the ductile failure of a tension specimen. Local description of material damage in metal forming is essential for developing realistic computer models. The DABY program possesses such a capability.