Role of Mineral NPK Fertilization and Nano-Zinc Foliar Application in Enhancing Greenhouse Tomato Growth and Yield: A Literature Review

Role of Mineral NPK Fertilization and Nano-Zinc Foliar Application in Enhancing Greenhouse Tomato Growth and Yield: A Literature Review

Sana Q. Hassan1, Afifullah Khan2, Hawraa Ali Abbas3, Mohammed M. Hamid4, Mohammed R. Ajeel5, * 1,4,5Department of Soil and Water Techniques, Technical College of Al-Mussaib, Al-Furat Al-Awsat Technical University, Iraq

2Department of Wildlife Sciences, Aligarh Muslim University

3of Field Crops, Coll. of Agric. Univ. of Karbala

Abstract – Managerial control of nutrients is required in greenhouse (plastic-house) tomato (Solanum lycopersicum L.) production due to high yields of tomatoes being produced under intensive irrigation and fertilization and excessive mineral fertilization may decrease the efficiency with which nutrients are used and may cause salinity accretion in the soils under protection. Nitrogen (N), phosphorus (P) and potassium (K) are the most commonly manipulated macronutrients under fertigation programs but the optimal levels and ratios differ according to the cultivar, substrate/soil characteristics, irrigation timing and environmental factors. Simultaneously, tomato growth and fruit set may be limited by zinc (Zn) deficiency and poor Zn bioavailability, which, in turn, is frequently increased by PZn antagonism. Zinc oxide nanoparticles (ZnO -NP) are also under investigation as high-efficiency foliar delivery agents; foliar delivery has proven to be an effective approach to correcting short-term deficiency; and the delivery of the nutrient via foliar has shown to be more effective compared to alternative methods like oral administration (Lee 2012). This review is based on the recent studies (mainly 20182025) on mineral NPK fertilizer approaches to accelerate the growth and yield of greenhouse tomatoes and the impact of nano-zinc foliar application on tomatoes physiology and productivity with plastic-house in mind. We synthesize documented optimum N levels, NPK ratios, as well as fertitation levels and we also compare ZnO -NP dosages implemented in tomato research, with concentration ranges that enhance growth and fruitfulness and phytotoxicity. Lastly, we report gaps in the research areas on integrating balanced NPK programs with nano-zinc foliar sprays under commercialized greenhouse circumstances and give a practical suggestion on the design of experimental and nutrient timing.

Keywords: Tomato; plastic greenhouse; fertigation; NPK; nitrogen use efficiency; zinc; zinc oxide nanoparticles; foliar spray; growth; yield.

1. INTRODUCTION

   Tomato as a protected crop is an excellent method to produce tomatoes all year round and achieve high yields and marketable crops; however, the technique is also associated with nutrient concentration in limited geographical spaces and short crop rotation. Frequent fertilization with minerals without strict observance of timing and proportions of irrigation, and availability of nutrients such as nitrogen and phosphorus, leads to a rise in soil electrical conductivity (EC), decreased nutrient uptake efficiency, and lowered yield. Accordingly, precision fertilization especially through drip fertilization is a major pillar in sustainable management of greenhouse tomatoes. (Wang et al., 2024)

   The fertitious provision of Macronutrients (N, P, K) is usually provided in fixed recipes of the nutrient or through the use of stage-based programs which monitor the demand of the plant. Various scientific researches indicate a similar result that yield returns reduce after nutrient becomes available beyond crop uptake, and excess of N also encourages vegetative growth at fruit weight disadvantage. Zn and other micronutrients may also inhibit tomato growth in alkaline soils and in soilless media when solution chemistry partially decreases the availability of Zn. Since high P-inputs have

   the capability of decreasing Zn- bioavailability, the P-Zn interaction has special consideration in the intensive greenhouse fertilization. (Nath et al., 2024)

   Nanofertilizers have attracted growing interest, and regardless of the fact that foliar Zn has long been treated with foliar Zn fertilizers (e.g., ZnSO 4, Zn -EDTA), experiments with ZnO nanoparticles (e.g., ZnO -NPs) as potential sources of foliar Zn have been discussed over decades. In tomato, evidence has shown that the right amounts of ZnO -NP may induce higher photosynthesis, biomass and yields characteristics, but inappropriate amounts may lead to oxidative stress and cause growth inhibition. The current review incorporates the latest literature of greenhouse that involves the use of mineral NPK fertigation, nano-zinc foliar application focusing on the growth and yield measures in tomatoes growing in plastic-house. (Ravishankar et al., 2025).

2. LITERATURE SEARCH STRATEGY

   Scopus, Web of science, Google Scholar, and publisher platforms (MDPI, Elsevier/ScienceDirect, Springer) were searched in literature. Searchers were using greenhouse tomato/ plastic house + fertigation, NPK, nitrogen rate, nutrient solution, zinc foliar, and ZnO nanoparticles. Peer-reviewed sources and reviews (20182025) were prioritized, and few older greenhouse fertigation studies were incorporated to put nutrient-use efficiency in perspective.

3. NUTRIENT DEMAND AND GROWTH STAGES IN GREENHOUSE TOMATO

   Demands of nutrients: nutrient requirements of tomatoes are stage-dependent: Seedlings need to have a moderate external supply of N, and in the process of rapid vegetative growth and premature fruit set, N and K are required more; greenhouse experience indicates that the use of fertilizers is better through the fruiting phase than during the substantial basal phase. Excessive N application above optimum uptake periods decrease nitrogen-use efficiency and does not always enhance yield. (Liu, et al., 2025).

4. MINERAL NPK FERTILIZATION IN PROTECTED TOMATO

   1. Nitrogen (N)

      N stimulates the growth of canopies, chlorophyll and the ability to photosynthesize. The usual response to yield is quadratic: it rises with N reaching an optimum and then levels off or decreases with higher rates because of the overgrowth of vegetation and the corresponding decrease in weight of the fruit. (Cheng et al., 2021).

   2. Phosphorus (P)

      P facilitates early root development, energy transfer (ATP) and reproductive development. But overabundance of P may counteract Zn absorption making Zn deficiency hidden even with moderate soil Zn. Both yield and Zn nutrition would hence be concerned with stage-appropriate P supply. (Lu et al., 2024).

   3. Potassium (K)

      K controls osmoregulation and the assimilate transportation, and plays a vital role in the process of fruit expansion. Several fertitation programs raise K after flowering, yet extremely high K may elevate solution EC, so K ought to be regulated with irrigation timing and leaching control. (Imtiaz et al., 2023).

5. EVIDENCE ON NPK FERTIGATION EFFECTS ON GROWTH AND YIELD

   The consistent reports in the literature of the studies on the use of protected-tomatoes are that yield is positively correlated with an increase in the NPK concentration to a certain threshold, and nutrient uptake efficiency decreases with excess supply relative to demand by the plant. Fertilizing at 200 per cent of crop uptake in place of 100 per cent may result in small increases in yield but significant decreases in uptake efficiency. Recent reports note that scheduling of irrigation and high-frequency fertigation (with sensor-based methods) are important leverages to enhance yield and nutrient-use efficiency. (Khapte et al., 2022).

6. NANOZINC FOLIAR APPLICATION IN TOMATO

   1. Zinc functions relevant to growth and yield

      Zn is cofactor to many enzymes and regulating proteins and aids in the production of auxin, membrane integrity and oxidative-stress resistance. Poor Zn levels may decrease the leaf area, photosynthesis, pollen viability and fruit set in tomato. Foliar application offers fast remediation in cases of limited root uptake by pH, salinity or nutrient antagonism. (Hamzah Saleem et al., 2022).

   2. Why ZnO nanoparticles

      ZnO -NPs are examined as nanofertilizer since nanoscale materials have the potential of enhancing the leaf surface coverage and residence time and may increase uptake through stomata and cuticular routes. Dose optimization and risk assessment are however necessary. (Raha and Ahmaruzzaman, 2022).

   3. Concentration windows and phytotoxicity

      Tomato studies often report beneficial effects in the ~25100 mg L¹ (ppm) range depending on formulation and context, while higher concentrations can increase oxidative stress markers and suppress growth. Greenhouse protocols should start conservatively and include phytotoxicity monitoring. (Collins et al., 2022)

7. EVIDENCE ON ZNONPS AND TOMATO YIELD

   In a glasshouse comparison of conventional Zn fertilizer (0.150.25%) versus ZnONPs (75125 ppm), 100 ppm ZnONPs produced the highest photosynthetic rate and the highest fruit yield per hectare, while higher conventional Zn rates reduced yield. Variety also mattered: MARDI Tomato3 generally yielded slightly more than MARDI Tomato1. (Pathania, 2025)

   Stresscontext studies indicate ZnONPs can improve biomass and physiology under drought and salinity, potentially stabilizing yield under suboptimal greenhouse conditions, although many reports do not include fullseason yield. (Singh et al., 2024)

8. INTERACTIONS BETWEEN NPK NUTRITION AND ZINC AVAILABILITY

   PZn antagonism is widely documented: excessive P can reduce Zn solubility and plant uptake, while high Zn can also disturb P translocation. Reviews recommend balanced fertilization and integrated nutrient management. In greenhouse systems with high P legacy levels, foliar Zn or nanoZn may bypass rootzone constraints, but longterm solutions require adjusting P inputs to realistic crop needs. (Yang et al., 2023)

9. PRACTICAL IMPLICATIONS FOR PLASTICHOUSE TOMATO

   Evidencebased principles for nutrient management experiments and practice include: (i) soil/substrate and irrigationwater testing; (ii) split N and K supply via fertigation; (iii) optimizing irrigation scheduling and frequency before increasing fertilizer concentration; (iv) avoiding excessive P to prevent Zn limitation; and (v) using conservative ZnONP doses (2550 ppm pilot; 75100 ppm commonly effective) with phytotoxicity monitoring. Apply foliar Zn during cooler hours and follow local safety guidance for handling nanoparticle formulations. (Zhao et al., 2024)

10. RESEARCH GAPS AND FUTURE DIRECTIONS

    Gaps include limited factorial studies combining stagebased NPK fertigation with nanoZn under commercial plastichouse conditions, insufficient nanoparticle characterization reporting, and limited multiseason data on the environmental fate of Zn from nanofertilizers. Future research should standardize ZnONP characterization, integrate plant diagnostics (leaf/root analysis), and evaluate yield stability across seasons and cultivars. (SH, 2023)

11. CONCLUSIONS

Mineral NPK fertigation is essential for high greenhouse tomato productivity, but yield gains diminish when nutrient supply exceeds plant uptake and nutrientuse efficiency declines. Optimizing irrigation scheduling and fertigation frequency can achieve high yield with reduced inputs. Nanozinc foliar application (typically 25100 ppm ZnONPs) shows promise for enhancing physiological performance and yield attributes, particularly where Zn availability is

constrained. Combining balanced NPK programs with carefully dosed nanoZn sprays is promising, but more productionscale, multiseason trials are needed to confirm consistent yield benefits and address safety considerations. (Bentamra et al., 2023)

Table 1. Representative studies on mineral NPK fertigation and/or foliar nanozinc in protected tomato (focus: growth and yield).

Table 2. Cultivar and system differences reported in selected protectedtomato fertilization/nanozinc studies.

Table 3. Selected evidence on mineral fertilization strategies and vegetative growth indicators.

Table 4. Selected evidence on foliar ZnONPs and physiological growth indicators.

Table 5. Yield responses to mineral fertilization strategies in protected tomato (selected examples).

Table 6. Yield responses to foliar Zn and ZnONPs in tomato (selected examples).

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