Quality and maximum profit of industrial tomato as affected by distribution uniformity of drip irrigation system

Abstract

Abstract. The tomato industry reformed its system of payment by weight of tomato, introducing a corrective system based on percent level of fruit dry matter produced. Such a decision implies significant changes in the management of irrigation systems, with a need to emphasize the technological quality of the marketable product. Three levels of distribution uniformity of the irrigation system are analysed, and related production functions of crop yield and percent of dry matter are presented as well as their use on the optimisation of dry matter, expected revenues and seasonal applied water. Results are critically influenced by the distribution uniformity. They demonstrate the inter-relationship between crop production, percent fruit dry matter and irrigation management, and the importance of considering non-uniformity in the economic analysis of industrial tomato production. Decreases in uniformity lead to a reduction in dry matter production per unit land. Decreases in dry matter are also observed with increasing levels of seasonally applied water, with the optimal level always lower than the required for maximum yield. Such interaction suggests a continuous and inverse relationship between profit and water applied. However, due to the corrective system of payment, by levels of percent of dry matter produced, for some uniformity, the expected revenue follows the yield-water production function instead of the dry matter function. This fact introduces disturbances in the optimal water applied inducing higher than expected levels of water applied for profit maximisation. The simulated data also show that incentives to switch to new systems or management practices able to raise the distribution uniformity result more from profit losses than increases in water price.

Desempenho de sistemas de rega

“…Também seguindo estes conceitos se desenvolveu um modelo de simulação e projecto para gota-a-gota e micro-aspersão (Pedras, 1997). A relação entre uniformidade, produção e rendimento foi explorada por Santos (1996) para o tomate de indústria.…”

“…A nível da parcela, tem havido várias tentativas de formulação de relações entre desempenho e rendimento, de que são exemplos os trabalhos de Seginer (1987) e de Warrick e Yates (1987) e, entre nós, os de Sousa et al (1993) para rega de superfí-cie, e de Santos (1996) para a microrrega. No entanto, têm sido utilizados apenas relações polinominais, cujos parâmetros são específicos, tornando impossível as generalizações obtidas.…”

Influencing factors and characterization methods of the anti‐clogging ability of labyrinth channel emitters

“…Due to this narrow channel structure, suspended particles, microorganisms, organics and other impurities in the irrigation water are easily adsorbed and deposited on the channel wall, which easily leads to emitter clogging, that is, the flow of the emitter decreases or there is no flow at all (Nakayama & Bucks, 1991; Pei et al, 2014). Emitter clogging directly affects the irrigation and fertilization uniformity of drip irrigation systems (Zhang et al, 2017), which directly affects the drip irrigation system service life and application benefits and leads to a reduction in crop growth uniformity (Oron et al, 1991; Santos, 1996), which in turn affects crop growth conditions, yield and quality (Contreras et al, 2020; Guan et al, 2019). Therefore, emitter clogging has become an important influencing factor limiting the promotion and application of drip irrigation technology.…”

MIRRIG: A decision support system for design and evaluation of microirrigation systems

“…upon the uniformity of water application, both of which affect crop yields (Santos, 1996;Hanson et al, 2006). If water is applied with low uniformity, some parts of the cropped field will receive more water and nutrients than others.…”