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The global population is expected to continuously rise and reach to nearly 10 billion people by 2050, and agricultural production needs to be doubled to feed this rapidly growing population. Drought, induced mainly by climate change and agricultural mismanagements, has severe negative impacts on crop yields and is a major challenge for achieving sustainable food and nutritional security in the world. Tomato (Solanum lycopersicum L.) is the second most important vegetable crop in the world in outdoor fields and greenhouses after potato (Solanum tuberosum L.). Grape tomato (Solanum lycopersicum L. var. cerasiforme) is popular worldwide for its flavor, sweetness, nutritional values, and health benefits. It has longer shelf life due to its thick skin making it less prone to damage. Grape tomato is cultivated both in the outdoor fields and in the greenhouse conditions where it is exposed to a combination of biotic and abiotic stresses. Water deficit is one of the major abiotic stresses, which can reduce tomato yield by as high as 50%. A high susceptibility of grape tomato to water-deficit stress warrants for management options to maintain or increase its productivity under limited water availability. Therefore, application of innovative agronomic management practices (nutrient management) coupled with plant biostimulant (phytohormone), and adoption of efficient water management strategies need to be integrated with existing cultivation practices to enhance crop tolerance against drought stress and maximize crop yield and water productivity for ensuring sustainable tomato production. Therefore, an interactive effect among nutrient management practice, biostimulant application, and irrigation water regime was evaluated through several polyhouse experiments for grape tomato.In the first polyhouse experiment, two studies were conducted to assess the effects of salicylic acid (SA) applied as a foliar spray and as a seed priming material on growth, yield, and fruit quality of grape tomato under drought stress. In the first study, SA was applied as a foliar spray in five doses (0, 50, 100, 150, and 200 mg L{u2013}1) under three soil moisture regimes (50%, 75%, and 100% FC). In the second study, doses of SA and soil moisture regimes were the same as first study, except that SA was applied as a seed priming material. Data on growth, fruit yield, and quality of grape tomato were collected. The results revealed that severe moisture deficit of 50% FC adversely affected growth and fruit yield of grape tomato by 94% in study 1 (foliar application of SA) and by 95 % in study 2 (seed priming of SA) compared with 100% FC, while fruit quality parameters (fruit pH, total soluble solids, and color index) improved with reducing soil moisture regime. Exogenous application of SA at 150 mg L{u2013}1 as a foliar spray enhanced fruit yield by 41% and at 100 mg L{u2013}1 as a seed priming material resulted in 33% increase in fruit yield compared with the control. However, there was no effect of SA supplementation at severe moisture deficit of 50% FC regardless of experiments and doses. Foliar application of SA at 150 mg L{u2013}1 resulted in statistically similar yields between moderate soil moisture level of 75% FC and sufficient soil moisture level of 100% FC, whereas in case of seed priming treatment, maximum fruit yield was obtained at 100 mg L{u2013}1 SA dose in combination with 100% FC. Grape tomato yielded more with foliar application of SA (113.1 g plant{u2013}1 fruit yield at 150 mg L{u2013}1) than did with SA seed priming (87.8 g plant{u2013}1 fruit yield at 100 mg L{u2013}1). Exogenous application of SA at 150 mg L{u2013}1 as a foliar spray and at 100 mg L{u2013}1 as a seed priming material could be recommended when grape tomato is grown under moderate to sufficient soil moisture availability.In the second polyhouse experiment, two studies were conducted to evaluate the effect of seed priming and soil application of silicon (Si) on growth, fruit yield, quality, and irrigation water productivity of grape tomato under drought stress. In the first study, Si in the form of monosilicic acid (MSA [H4SiO4]) was applied as a seed priming material in five doses (0, 0.063, 0.125, 0.25, and 0.5 mM) under three soil moisture regimes (50%, 75%, and 100% field capacity [FC]). The second study consisted of five MSA doses applied as soil incorporation (0, 75, 150, 300, and 600 kg ha{u2013}1) under the same soil moisture regimes used in the first study. The results revealed that fruit yield and irrigation water productivity were severely affected by soil moisture deficit at 50% FC, while fruit quality was better at this soil moisture level. Fruit yield was reduced by 95% at 0 mM MSA priming dose at 50% FC compared with fruit yield at 0.25 mM MSA priming dose at 100% FC in the first study. In the second study, soil incorporation of MSA at 300 kg ha{u2013}1 in combination with 100% FC maximized fruit yield, which was reduced by 96% at 0 kg ha{u2013}1 MSA dose in combination with 50% FC. Exogenous application of MSA at 0.25 mM as a seed priming material and 300 kg ha{u2013}1 as soil incorporation (60 kg ha{u2013}1 soluble Si) also resulted in better fruit yield and irrigation water productivity at 75% FC. Priming seeds of grape tomato with MSA at 0.25 mM or soil incorporating with 300 kg ha{u2013}1could be recommended to enhance fruit yield of grape tomato grown under soil moisture regime fluctuating between sufficient (100% FC) and moderate soil moisture availability (75% FC).The third factorial experiment was conducted to evaluate the effect of Si and organic manure (OM) on growth, physiological traits, fruit yield, and fruit quality of grape tomato under water-deficit stress. The experiment consisted of seven different fertilizer doses of Si and OM combined with or without nitrogen (N) and phosphorus (P) [control (100% NP), 100% NP + 100% OM, 100% NP + 100% Si, 100% NP + 100% OM + 100% Si, 75% NP + 25% OM + 100% Si, 50% NP + 50% OM + 100% Si, and 100% OM + 100% Si] and three soil moisture regimes (100%, 75%, and 50% FC). Decreasing soil moisture was equally detrimental for all fertilizer doses, which caused 86{u2013}94% decrease in fruit yield and 79{u2013}92% decrease in irrigation water productivity at 50% FC compared with 100% FC. However, the same soil moisture level (50% FC) increased fruit color index by 129% and total soluble solids content by 19% compared with 100% FC. Nevertheless, OM application along with the recommended doses of N and P (100% NP + 100% OM) resulted in better response of grape tomato with 38% higher root dry matter, 21% higher individual fruit weight, 98% higher fruit number plant{u2013}1, 145% higher fruit yield, 159% higher irrigation water productivity, and 31% lower proline content compared with the control. This response was at large similar with 100% NP + 100% OM + 100% Si and 50% NP + 50% OM + 100% Si at 100% and 75% FC, especially for fruit yield and irrigation water productivity. Hence, supplementing OM along with the recommended or even half of the recommended doses of N and P as well as a supplementation of Si could be a feasible option for grape tomato cultivation under moderate water-deficit stress of up to 75% FC. Growth and yield reduction at 50% FC could not be compensated for application of OM or Si. |
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