Converting simulated total dry matter to fresh marketable yield for field vegetables at a range of nitrogen supply levels

Simultaneous analysis of economic and environmental performance of horticultural crop production requires qualified assumptions on the effect of management options, and particularly of nitrogen (N) fertilisation, on the net returns of the farm. Dynamic soil-plant-environment simulation models for agro-ecosystems are frequently applied to predict crop yield, generally as dry matter per area, and the environmental impact of production. Economic analysis requires conversion of yields to fresh marketable weight, which is not easy to calculate for vegetables, since different species have different properties and special market requirements. Furthermore, the marketable part of many vegetables is dependent on N availability during growth, which may lead to complete crop failure under sub-optimal N supply in tightly calculated N fertiliser regimes or low-input systems. In this paper we present two methods for converting simulated total dry matter to marketable fresh matter yield for various vegetables and European growth conditions, taking into consideration the effect of N supply: (i) a regression based function for vegetables sold as bulk or bunching ware and (ii) a population approach for piecewise sold row crops. For both methods, to be used in the context of a dynamic simulation model, parameter values were compiled from a literature survey. Implemented in such a model, both algorithms were tested against experimental field data, yielding an Index of Agreement of 0.80 for the regression strategy and 0.90 for the population strategy. Furthermore, the population strategy was capable of reflecting rather well the effect of crop spacing on yield and the effect of N supply on product grading

CLIMA: a component-based weather generator

Investigating the potential impact of climate on agro-ecosystems using simulation models is underpinned by the availability of climate data at the appropriate temporal scale (daily or higher resolution). The production of artificial series of weather data has traditionally adopted a variety of alternative methods. These range from empirical functions where simple relationships between weather variables are used to estimate missing data from available data, to sophisticated approaches where physically-based models are used. All such approaches illustrate from different perspectives that there is actually a wealth of well developed solutions to the basic problem of estimating or generating weather data, coded in

Optimisation of vertically mounted agrivoltaic systems

Agrivoltaic systems represent a key technology for reaching sustainable development goals, by reducing the competition of land used for food versus land used for electricity. Moreover, agrivoltaic systems are at the centre of the nexus between electricity production, crop production, and irrigation water savings. In this study, an optimisation model for vertically mounted agrivoltaic systems with bifacial photovoltaic modules is developed. The model combines three main sub-models: solar radiation and shadings, photovoltaics, and crop yield. Validation of the sub-models is performed showing good agreement with measured data and commercial software. The optimisation model is set as multi objective to explore the trade-offs between competing agrivoltaic key performance indicators. Oats and potatoes are used as reference crops in this study. The results show that the row distance between bifacial photovoltaic module structures significantly affects the photosynthetically active radiation distribution. The resulting crop yield of oats and potato is reduced by about 50% as row distance decreases from 20 m to 5 m. The implementation of an agrivoltaic system for the investigated crops at the chosen location shows a land equivalent ratio above 1.2, which justifies the use of the technology for reaching national sustainability goals

Hormonal and climatological aspects of dormancy in peach buds

Hormonal changes in leaf and flower buds of Prunus persica (L.) Batsch. (cv 'Springcrest'/seedling) occurring during the 1988/89 and 1989/90 rest periods were studied under three different climatic conditions, i.e. in north-eastern (Udine), central (Pisa) and southern (Palermo) Italy. 1H-indole-3-acetic acid (IAA), abscisic acid (ABA), and t-zeatin riboside (t-ZR) levels were determined by immunoassay using a McAb-ELISA kit. The end of dormancy was evaluated by forcing 1-year shoots collected from the three locations at intermittent periods during rest and monitoring percentage of budbreak. Chilling was estimated according to Fishman et al. (1987), while heat units accumulation was calculated according to Anderson et al. (1986). The IAA content dropped concurrently with the start of chilling accumulation and remained low throughout a large part of the rest period; an increase in auxin content was concurrent with tetrads formation, a phenomenon that did not appear to be related to the end of dormancy. ABA concentration in buds collected in Udine and Pisa was high during the early part of the rest period and then gradually declined, reaching the minimum concentration at budbreak. In Palermo, ABA content increased until the end of December, then gradually declined. No association was found between ABA level and release from dormancy, t-ZR level, low throughout the rest period, increased at bud swelling

Variety earliness effect on field drying of biomass sorghum

A major constraint to the use of biomass sorghum varieties (Sorghum bicolor (L.) Moench) to generate electricity by direct combustion is the high biomass moisture content at harvest that, under unfavourable weather conditions during field drying limits the possibility to achieve a suitable moisture content for baling. In this work, the CropSyst model was calibrated and validated with data collected in experimental trials conducted in the Po Valley (northern Italy). It was then used to simulate biomass production of three sorghum varieties of contrasting earliness (early, medium-late, and late). In order to simulate the dynamics of biomass moisture content during field drying, a specific model, “sorghum haying model” was developed and validated. The two models combined were used to simulate, for three sorghum varieties of contrasting earliness (early, medium-late and late), biomass production and the probability to achieve during field drying a biomass moisture content suitable for baling. In a long term simulation (140 years), the late sorghum variety achieved the highest dry biomass production (16.5 Mg ha−1) followed by the medium-late (15.4 Mg ha−1) and early (15.1 Mg ha−1) variety. The early variety had the highest probability (0.66) of being baled at a moisture content ≤ 18%, followed by the medium-late (0.53) and late (0.37) varieties. The early variety, also having the shortest average field drying (9.2 days), was considered the most suitable for the selected environmental conditions

Effect of irrigation and nitrogen fertilization on the production of biogas from maize and sorghum in a water limited environment

tThe expansion of biogas production from anaerobic digestion in the Po Valley (Northern Italy) has stim-ulated the cultivation of dedicated biomass crops, and maize in particular. A mid-term experiment wascarried out from 2006 to 2010 on a silt loamy soil in Northern Italy to compare water use and energyefficiency of maize and sorghum cultivation under rain fed and well-watered treatments and at tworates of nitrogen fertilization. The present work hypothesis were: (i) biomass sorghum, for its efficientuse of water and nitrogen, could be a valuable alternative to maize for biogas production; (ii) reductionof irrigation level and (iii) application of low nitrogen fertilizer rate increase the efficiency of bioenergyproduction. Water treatments, a rain fed control (I0) and two irrigation levels (I1 and I2; only one in2006 and 2009), were compared in a split\u2013split plot design with four replicates. Two fertilizer rates werealso tested: low (N1, 60 kg ha 121of nitrogen; 0 kg ha 121of nitrogen in 2010) and high (N2, 120 kg ha 121of nitrogen; 100 kg ha 121of nitrogen in 2010). Across treatments, sorghum produced more abovegroundbiomass than maize, respectively 21.6 Mg ha 121and 16.8 Mg ha 121(p < 0.01). In both species, biomass yieldwas lower in I0 than in I1 and I2 (p < 0.01), while I1 and I2 did differ significantly. Nitrogen level neveraffected biomass yield. Water use efficiency was generally higher in sorghum (52 kg ha 121mm 121) than inmaize (38 kg ha 121mm 121); the significant interaction between crop and irrigation revealed that water useefficiency did not differ across water levels in sorghum, whereas it significantly increased from I0 and I1to I2 in maize (p < 0.01). The potential methane production was similar in maize and sorghum, while itwas significantly lower in I0 (16505 MJ ha 121) than in I1 and I2 (21700 MJ ha 121). The only significant effectof nitrogen fertilization was found in the calculation of energy efficiency (ratio of energy output andinput) that was higher in N1 than in N2 (p < 0.01). These results support the hypothesis that (i) sorghumshould be cultivated rather than maize to increase energy efficiency, (ii) irrigation level should replace upto 36% of ETr and (iii) nitrogen fertilizer rate should be minimized to maximize the efficiency in biomassproduction for anaerobic digestion in the Po Valley

The use of hand-held chlorophyll meters as a tool to assess the nitrogen status and to guide nitrogen fertilization of potato crop

Fifteen experiments were carries out in different sites of Italy, Belgium, Scotland and The Netherlands from 1995 to 1999 to study the possible use of chlorophyll meter to assess the nitrogen status and to ghuide nitrogen fertilization of the potato crop. The results are gathered here and reviewed together with the available information in literature. The paper deals with measuring principles of chlorophyll meter; relation between chlorophyll meter readings and analytical measurements of chlorophyll , analytical measurements of nitrogen content, tuber yield, and physiological processes in leaves; variations in chlorophyll meter readings related to nitrogen supply, potato cultivar, crop management, and sampling methods; use of chlorophyll meter readings for decision making in the management of supplemental nitrogen fertilization (assessment of chlorophyll meter critical threshold, plant response to addition of supplementary N)