Integrative Effect of Protective Structures and Irrigation Levels on Tomato Performance in Indian Hot-Arid Region

Abstract

Protected cultivation is gaining momentum in (semi) arid regions to ameliorate the adverse environmental impacts on vegetable crops, besides ensuring high resource use efficiency in resource-limiting environments. Among the less techno-intensive protected cultivation structures, naturally ventilated polyhouses (NVP), insect-proof net houses (IPN) and shade net houses (SNH) are commercial structures in India. With the aim to find the best-protected structure, together with optimum irrigation level, for high yield and water productivity of the tomato crop, the most popular crop in hot arid regions, we evaluated tomato performance in low-tech protected structures (NVP, IPN and SNH) in interaction with three irrigation levels (100, 80 and 60% of crop evapotranspiration, ETc) during spring–summer of 2019 and 2020. The NVP was found superior to both the net house structures (IPN and SNH) for different performance indicators of tomatoes under investigation. The components of plant growth (leaf and stem dry mass) and fruit yield (fruit size, weight, yield), as well as fruit quality (total soluble solids, fruit dry matter and lycopene content) were higher in NVP, regardless of irrigation level. The yield as well as water productivity were significantly higher in NVP at 100% ETc. However, there was no statistical variation for water productivity between NVP and IPN. Microclimate parameters (temperature, relative humidity and photosynthetic active radiation) were markedly more congenial for tomato cultivation in NVP followed by IPN in relation to SNH. Consequently, plants’ physiological functioning with higher leaf relative water content (RWC) and lower leaf water potential concomitantly with better photosynthetic efficiency (chlorophyll fluorescence, Fv/Fm), was in NVP and IPN. Most growth and yield attributes were depressed with the decrease in water application rates; hence, deficit irrigation in these low-tech protected structures is not feasible. For tomato cultivation in resource-scarce arid regions, the combination of the normal rate of irrigation (100% ETc) and NVP was optimal for gaining high yield as well as water productivity as compared to net houses.

Optimization of Low-Tech Protected Structure and Irrigation Regime for Cucumber Production under Hot Arid Regions of India

“…The better plant growth in NVP seemed to be due to the more congenial microenvironment observed inside plastic-covered structures than screen/net-covered structures in IPS or SHS. The pronounced growth observed in greenhouse cucumber plants [ 35 ] and tomato plants [ 19 ] in previous studies was associated with a positively altered microclimate inside plastic-covered greenhouses. In net or screenhouses, only regulation in the amount of direct solar radiation falling onto the plants was possible, thereby causing shading effects which possibly hampered the plants’ physiological processes.…”

“…Although deficit irrigation has been widely recognized as an efficient tool to optimize water use in open-field cultivation [ 38 ] and fruit orchards [ 39 ], its advantage seems to be limited to protected cultivation, as evidenced from a significant reduction in different important growth attributes (e.g., leaf area, vine length, node number and shoot dry mass) under both moderate and severe water deficit conditions ( Table 4 ). A previous study on tomatoes grown under different protected environments also reports a significant reduction in shoot growth as well as fruit yield parameters under sub-optimal water supply conditions [ 19 ]. Furthermore, arid environments are characterized by not only limited precipitation but also by high evapotranspiration, which results in the accumulation of salts in the uppermost soil layer.…”

“…This is quite evident when observing a severe reduction in shoot dry mass, leaf area and vine length under SD in comparison with MD, regardless of the protected structures. In fact, under protected cultivation, vegetables are accustomed to a regular supply of water [ 41 ]; hence, plants receiving sub-optimal quantities of water under MD and SD could not meet their water demands to balance the simultaneous occurrence of vegetative and fruit growth [ 19 ]. This is why the conspicuous damaging effect of water shortage was obvious on various growth parameters, which was also reflected later on in the fruit yields.…”

“…The combination of a favorable microenvironment and adequate water supply to root zones in protected conditions has a direct influence on plant physiological processes and a subsequent effect on growth and yield parameters [ 19 ]. In the present study, both protected structures and irrigation levels significantly influenced the physiological status of cucumber plants.…”

“…Furthermore, the optical properties of the covering material also play a crucial role in influencing air temperature and humidity within the protected structures. These changes subsequently affect the photosynthetic efficiency [ 19 ] and respiratory needs of crops, potentially leading to alterations in water productivity [ 20 , 21 ]. It has been found that the modifications in light transmission, temperature, and vapor pressure deficits were more favorable in double-layer polyethylene-covered structures compared to those covered with UV-stabilized polyethylene, IR absorbers polyethylene, or normal polyethylene [ 22 ].…”