Luca Incrocci

Root Zone Sensors for Irrigation Management in Intensive Agriculture

Crop irrigation uses more than 70% of the world’s water, and thus, improving irrigation efficiency is decisive to sustain the food demand from a fast-growing world population. This objective may be accomplished by cultivating more water-efficient crop species and/or through the application of efficient irrigation systems, which includes the implementation of a suitable method for precise scheduling. At the farm level, irrigation is generally scheduled based on the grower’s experience or on the determination of soil water balance (weather-based method). An alternative approach entails the measurement of soil water status. Expensive and sophisticated root zone sensors (RZS), such as neutron probes, are available for the use of soil and plant scientists, while cheap and practical devices are needed for irrigation management in commercial crops. The paper illustrates the main features of RZS’ (for both soil moisture and salinity) marketed for the irrigation industry and discusses how such sensors may be integrated in a wireless network for computer-controlled irrigation and used for innovative irrigation strategies, such as deficit or dual-water irrigation. The paper also consider the main results of recent or current research works conducted by the authors in Tuscany (Italy) on the irrigation management of container-grown ornamental plants, which is an important agricultural sector in Italy.

Modeling Salinity Build-Up in Recirculating Nutrient Solution Culture

Abstract This paper presents a simple model for the changes in ion concentration and electrical conductivity (EC) of the recirculating nutrient solution in a closed-loop soilless culture of tomato (Lycopersicon esculentum Mill.). The model was designed on the basis of a balanced equation for plant nutrient uptake: for macrocations (K+, Mg2+ and Ca2+), a linear dependence of concentration on crop water uptake was assumed, while for non-essential ions, such as sodium (Na+), a non-linear function was used. The model was developed for closed-loop hydroponic systems in which crop water uptake (namely, transpiration) is compensated by refilling the mixing tank with complete nutrient solution. In these systems, EC gradually increases as a result of the accumulation of macro-elements and, principally, of non-essential ions, like Na+, for which the apparent uptake concentration (i.e., the ratio between nutrient and water uptake) is lower than their concentration in the irrigation water. For model calibration, data from both the literature and a previous work were used, while validation was performed with data from original experiments conducted with tomato plants in different seasons and using water with different sodium chloride (NaCl) concentrations (10 and 20 meq/L). The results of validation indicate that the model may be a useful tool for the management of closed-loop hydroponics, because it simulates rather well the salt accumulation that occurs in the recirculating nutrient solution when it is prepared with irrigation water of poor quality. Furthermore, the model is able to estimate the amount of crop evapotranspiration that leads to a value of EC at which flushing is necessary, thus enabling one to predict the water and nitrogen runoff of the semi-closed soilless culture.

Empirical Models of Macronutrient Uptake in Melon Plants Grown in Recirculating Nutrient Solution Culture

Abstract The article presents a number of empirical models for predicting the macronutrient uptake of melon plants grown in nutrient film technique under environmental conditions of plastic greenhouse in the Mediterranean region. Models were developed according to two statistical procedures: stepwise multiple regression (MR) and canonical correlation (CC). Independent variables considered by the modeling were global radiation and air temperature in the greenhouse, crop age (expressed as number of weeks from planting, growing degree days and photo-thermal units), and the uptake of water as well as of a guide-ion that could be routinely measured manually by means of easy-to-use test-kits or automatically with chemo-sensors. The best models, as selected on the basis of determination coefficient and the correlation coefficient for the relationship between residuals and observations, explained only 36–72% of the variance in the mineral uptake, depending on the considered nutrient. Moreover, the models were conservative, as predicted values tended to be less extreme with respect to the observed values and the residuals were positively correlated to the observations. The results of MR and CC were similar, although the validation of the models derived from CC produced better results compared to MR. The models provided evidence for the close relationship between ion and water uptake and indicated the possibility to predict the crop mineral requirements on the basis of the consumption of a guide-ion (i.e., nitrogen).

A comparison between two methods to control nutrient delivery to greenhouse melons grown in recirculating nutrient solution culture

Abstract Two methods to control nutrient delivery to greenhouse melon plants grown with the nutrient film technique were compared: a conventional control system based on the adjustment of electrical conductivity (EC) of the recirculating nutrient solution, and a programmed nutrient addition, which was based simply on pre-established weekly supply of N, P and K without any attempt to maintain constant values of nutrient concentration and EC. The method to control nutrient supply did not influence significantly fruit yield or quality, but the nutrient addition reduced the crop consumption of water, N, P and K by 40–60% with respect to the EC method.

Short communication: Soil-less indoor-grown lettuce (Lactuca sativa L.): Approaching the modelling task

Process-based modelling approaches developed for field crops were adapted to address the behaviour of indoor-grown soil-less lettuce under alternative growth conditions. The equations for crop growth and development were simplified to common and consistent terms, re-designed against the peculiarities of a controlled environment and implemented into an easy-to-use, management-oriented, software tool. An array of experiments, where lettuce was grown in growth chambers under water- and nutrient-unlimited conditions, at various temperature and radiation levels, was performed to build a data set to evaluate the model. Critical parameters and suitable relationships were identified and evaluated for possible use in management-oriented applications. Summary statistics of the evaluation indicated a satisfactory description of crop growth (EF>0.50) and development (+/-1 day discrepancy). As a result, there is a potential for the present approach to be applied to soil-less lettuce systems under alternative management options.

RESPONSE TO SODIUM CHLORIDE SALINITY AND EXCESS BORON IN GREENHOUSE TOMATO GROWN IN SEMI-CLOSED SUBSTRATE CULTURE IN A MEDITERRANEAN CLIMATE

The effects of sodium chloride (NaCl) salinity and boron (B) toxicity were investigated in greenhouse tomato (Solanum lycopersicum L.) plants grown in closed soilless culture under the typical climatic conditions occurring in the Mediterranean regions. The experiment was conducted under semi-commercial conditions. Two NaCl (2.0 and 10.0 mol m−3) and B (27.8 and 185.0 mmol m−3) concentrations were combined to produce four different types of raw water used to prepare the nutrient solutions. The fertigation treatment did not affect significantly the uptake of water and mineral elements apart from that of sodium (Na), chloride (Cl), and B. The use of B-enriched water increased the accumulation of this element in the leaves, which showed marginal chlorosis and necrosis within 35–40 days from planting. No or minor effects of NaCl and B concentrations in the irrigation water were found on leaf area development, biomass accumulation, crop yield and fruit quality.

Managing Mineral Nutrition in Soilless Culture

In most cases, rooftop agriculture uses soilless cultivation (or hydroponics) of plants, as the yield and the quality of the soilless-grown crops are often higher than those grown in the agricultural soil. In soilless culture, the elements that are essential or beneficial for plant growth and development are supplied through: (i) the addition of organic and/or synthetic fertilisers to the substrate before and after crop plantation; (ii) the supply of a nutrient solution, which is prepared dissolving one or more soluble fertilisers in the raw water and thus is delivered with the irrigation system (fertigation). In this chapter, the basic aspects of the mineral nutrition of hydroponically-grown plants and the methods that could be used for a sustainable management of fertigation in rooftop soilless culture and to improve the organoleptic and nutritional quality of rooftop food crops are described.

Aquaponic as sustainable innovation for food production

To better understand aquaponic, it is important to describe the socio-demographic context and the role of agriculture in a future perspective. Due to the increasing world population, by 2050 food production should be increased of not less than 70%. Nowadays the agriculture sector is playing a key role in ensuring food security and in the upcoming context it should also face one of the greatest dilemmas of the modern age, which consist in producing more food using less resources and minimizing the environmental impacts. To cope with this challenge, the aquaculture technology seems to be one of the most suitable production systems able to face this dilemma. In this paper, the technical and technological aspects of the Integrated Aquaponic System (IAS) are described. The integration of an aquaponic system with algae, worms and insects production it is also suggested for improving sustainability.

Modelling Evapotranspiration of Container Crops for Irrigation Scheduling

Irrigation is now recognized as an important component in the agriculture economy of Mediterranean regions. As practiced by many growers, it is often based on traditional application methods that fail to measure the supply of water needed to satisfy the variable requirements of different crops. In order to achieve more profitable and sustainable cropping systems, it is essential to modernize existing irrigation systems and improve irrigation water use efficiency (WUE). Up-to-date methods of irrigation should likewise be based on sound principles and techniques for attaining greater control over the soil-cropwater regime and for optimizing irrigation in relation to all other essential agricultural inputs and operations. Accurate predictions of crop water requirements are necessary for an efficient use of irrigation water in container crops cultivated both outdoors and in greenhouse. Irrigation scheduling (IS) has conventionally aimed to achieve an optimum water supply for productivity, with soil or container water content being maintained close to field capacity. Different approaches to IS have been developed, each having both advantages and disadvantages but despite the number of available systems and apparatus, not entirely satisfactory solutions have been found to rationalize IS, assuring optimal plant growth with minimal water use (Jones, 2004). Many growers, especially in the Mediterranean regions, use simple timers for automated irrigation control of containerized crops and scheduling is based on their own experience. Evapotranspiration (ET) is the primary process affecting crop water requirements and, therefore, its knowledge is essential for efficient irrigation management. ET is the combined process of evaporation from soil or substrate and leaf transpiration. Evapotranspiration requires two essential components: a source of energy and a vapour transport mechanism. Energy is needed for phase change from liquid to vapour in sub-stomatal cavities whereas the leaf-to-air vapour pressure gradient ensures that water vapour crosses leaf stomata. In container-grown plants, ET is affected by many factors, both environmental (e.g. air temperature, radiation, humidity, wind speed) and plant related characteristics (e.g. growth

State of the art and perspectives on application of mathematical models to greenhouse crops

An increasing trend was observed over the last years in the modelling of soil-plant-management interactions of protected crops, mainly as an adaptation of approaches originally developed for field crops. The variety of modelling approaches used world-wide reflects the difficulty of unifying physiological principles across various crops (plant types). The heterogeneity of software development techniques (typically based on procedural principles) has been another obstacle to the progress of research in this field, since it hampered model extension and re-usability. This paper describes and discusses the scientific basis, the design, implementation and perspectives in modelling greenhouse crops. Generic modular architectures developed according to up to date software technologies (.NET, Java) were identified and proposed as valuable for the design, implementation, verification and comparison of process-based modelling approaches. On this basis, the authors argue that the combination of good software engineering with sound crop science can enhance the rate of advance in crop modelling for protected crops.