Enhancing Potato Production by Applying Commercial Seaweed Extract (TAM®) Biostimulant under Field Conditions

INTRODUCTION

Potato (Solanum tuberosum L.) occupies the first world-widely staple source of starchy foods and the fourth dietary important crop after wheat, maize, and rice (Statista, 2019). While global production has estimated a sum of over 370 million metric tons in 2019 (Statista, 2019, FAO, 2021(b) the Food and Agriculture Organization of the United Nations ( FAO, 2008), has specified the year “2008” to celebrate the importance of potato crop, as being one of the most significantly consumed plants worldwide, and as a food security crop that provides a main supplement of complex carbohydrates on the international dining tables ( FAO, 2019(a).

Utilization of plant biostimulants nowadays as effective biomolecules, has been experiencing much scientific interest all over the world, with greater attention than any time ever before( Khanet al., 2009, Ali et al., 2021). This is because it provides one of the advances and most innovative technologies, used recently -with safe outlines- for boosting plant production, under harsh conditions, in parallel with striking world population that claims for sustained food resources(Khan et al., 2009, Jardin, 2015). It is highly expected that biostimulants would be acting as the “codeword” in the future of organic agriculture business and markets, at least for establishing a pioneer production of new Biofertilizers that can compete with classically applied ones in the fertilizers’ industry, through which worldwide governmental strategies will follow to secure riskless food and feed sources for their nations, as a novel trend for finer and healthier style of living (Kaur, 2020, Buono, 2021                 ). Biomolecules found in biological stimulants, and plant growth promotors (PGPs), sourced from bioagents, include plenty of beneficial substances. Numerus biological origins are prominent with compounds like proteins, organic and humus bountiful substances, while other bioactive molecules have been detected in seaweed and plant extracts, which were found to be rich sources of phytohormones, beneficial plant-growth-promoting microorganisms( Santiniet al .,2021  ), and mycorrhizal fungi as well (Jardin , 2015, Rouphaelet al.,  2015, Shukla et al., 2021). Such vital elements, are famous to be environmentally friendly, when being compared with traditionally practiced fertilizers, and have shown amazing capabilities in balancing the harmony of different antioxidant machinery, redox potential, and secondary metabolism in plants, leading to maximizing plant yields, thorough supportation of defense strategies, and supplementation with essential promotors, to afford various serious stresses (Hasanuzzaman,2020,Khan et al.,2009,Patel and Mukherjee,2021). Yet, physiological, biochemical, and molecular mechanisms, lying under the plant–biostimulant relationship symphony, within different environmental conditions, are so far unrevealed, and still have a lot to tell. Necessarily, encouragements for extra investigations are representing top-priorities to interpret the key-operating mechanisms, and the administrative functions of biostimulants (Buono,2021).

Unquestionably, involving seaweed foliar sprays in the modern organic agriculture programs, as parallel alternatives to conventional fertilizers, gives them a superior ad-vantage to sustain the obvious soars in extreme disease infections, and an unwanted fortuitously environmental stresses that occur as a direct result of climatic shifts(EL Boukhariet al.,  2020). This feature has been very handy, while for a lot of farming practices, traditional chemicals proved out to be a nuisance issue (Hasanuzzaman ,2020).

Lately, our team has investigated the impact of applying TAM® as a reliable supplement for crops like cucumber (Hassan et al., 2021(a), and pepper (Ashour et al.,2021). A part from that, previous investigated TAM® practices have been carried out under controlled greenhouse conditions. In this context, the innovative trend in the contemporary research work aimed mainly to complementary inspire the growth and yield production of potato plant (Solanum Tuberosum L., Spunta cv.), and at the same time, to evaluate its performance under normal field conditions, in order to exploiting the beneficial attributed magic properties of TAM® seaweed liquid extract, as a novel turn for practicing biostimulants application, in the form of foliar spray, along with comparative doses from classical N, P, and K, fertilizing protocol.

MATERIALS AND METHODS

Experimental Site

Two field experiments were conducted during the autumn seasons of 2017and 2018, at the Abu Al-Ela village, Al-Nahda area, Alexandria Governorate, Egypt, to investigate the effects of covenantal mineral N, P, and K fertilizers, and seaweed liquid extract (TAM®) on vegetative growth and morpho-physiological traits, mineral contents of leaves, tubers yield and quality characteristics, as well as tuber nutritional quality of potato (Solanum Tuberosum, Spunta cv.) which were obtained from Agro Food Co., Egypt.

Seaweed Liquid Extract Methods

TAM® is a commercial seaweed liquid extract, submitted as a patent (Garcés-Fialloset al.,  2021). The preparation of TAM® was followed as been described previously by (Ashour et al., 2020). In details, three seaweeds species, Ulva lactuca (Chlorophyceae), Janiarubens, and Pterocladiacapillacea (Rhodophyceae), were employed in preparing and producing TAM®. The selected species were collected in the 2016 summer season from the rocky site (31° 16′ 16.0″ N, 30° 10′ 28.0″ E) of Abu-Qir Bay, the Mediterranean Coast of Alexandria, Egypt. After being harvested, the epiphytic and waste materials were removed, and then samples were washed, air-dried, powdered, and finally kept in plastic bags at room temperature for further analysis. Phytochemical, physical, chemical, and biochemical analyses of crude TAM® were conducted and estimated as previously described by (Ashour et al., 2020) and (Hassan et al., 2021(a) Tables 1and 2 .

Table 1.:Physical, chemical and biochemical analyses of Seaweed Commercial Biofertilizer Extract (SCBE) used as foliar spray for Potato plant.

Table 2.:Phytochemical  compounds of (TAM) and  related biological activities according to the literature .

Experimental Design

Potato tuber seeds were planted on 25th of September in both seasons (2o17 and 2018). The experimental layout was, a randomized complete blocks design (RCPD), with three replicates. Each replicate included 3 plots . Each main plot contained three rows, each row was 4 m long, and 0.7 m wide, making a total main plot area of 8.4 m².

Soil Analysis

Preceding the initiation of each experiment, in both seasons, soil samples were collected, from the experimental site  before planting , at 15-30 cm depth, and analyzed at Faculty of Agricultural in Alexandria University analysis lab, for some soil’s physical and chemical properties according to the published procedures  (A.O.A.C, 1995, A.O.A.C International Arlington, 2019),  and are presented in Table 3.

Table 3: Soil physical and chemical properties of the experimental sites in the two growing autumn seasons of 2017and 2018

In the current experiment, two levels of crude TAM® foliar application (2.5 ml L^-1 and 5 ml L^-1) were applied as a 50 % replacement of the recommended NPK classical chemical fertilizer that added during the growing seasons. two treatments were applied three times every week after the fourth week from planting until harvest to compare a control 100 % NPK mineral fertilizer as follows; (1) T1: NPK100%, (2) T2: NPK50%+TAM2.5 mL L^-1, and (3) T3: NPK50%+TAM5 mL L^-1. The recommended NPK100% mineral fertilizer protocol consists of 300 kg fed^-1 of Ammonium Nitrate (33.5% N), added in three-time intervals 4, 7, and 10 weeks after planting, Phosphorus fertilizer was mixed during soil preparation 150 kg fed^-1 of calcium super phosphate (15.5% P2O5), as one dose at soil preparation time, 80 kg fed^-1 of Potassium Sulphate (48% K2O), added in two-time doses; i.e., after 7, and 10 weeks from planting. Other recommended agricultural practices were followed as commonly used in the commercial production for potato plant, and according to the Egyptian Ministry of Agriculture and Land Reclamation outlined potato fertilization program guidelines.

Tested Parameters

Vegetative growth characters

A random sample of five potato plants was taken from the first ridge of each plot, after 90 days of planting, to measure plant height, number of branch plant^-1, and plant fresh weight.

Mineral contents of leaves

Random samples of the youngest expanded mature leaves of potato plants, were randomly collected from each plot, then washed with distilled water, weighed, and hence after, oven dried at 70 °C till constant weight. The dried leaf materials were grinded and homogenized, wet digested; using concentrated sulfuric acid and H₂O₂, and the total nitrogen, and phosphorus of leaves of potato were determined calorimetrically; using spectrophotometer at 662 and 650 nanometers wavelength; according to (Evenhuis, 1976andMurphy and Riley,1962).

 Tubers’ yield and quality characters

 Harvesting potato plants was performed at 90 days after planting by the 20th of January. The harvested tubers from the 2^nd and the 3^rd ridges of each experimental unit were weighed, then graded into three sizes according to their diameter; small (< 30 mm), medium (30 - 60 mm) and large (> 60 mm). Total tuber yield ton fed^-1 was calculated for small, medium, and large . Total potato yield has been also calculated as well. In addition, other yield and quality characters like tuber weight, tuber length, and tuber diameter were measured.

 Tuber nutritional quality

Tuber sample from each plot was saved, to determine tuber dry matter contents, total sugar, (mg. g^─1.d.w) according to (Malik and Singh,1980 ), and starch percentage as described by (A.O.A.C, 1990) Moreover, total phenols measurement for the total free and conjugated phenols was determined according to Snell and Snell, 1953.

Statistical analysis

   All obtained data of the present study were, statistically, analyzed according to the technique of analysis of variance (ANOVA)for the RCBD as published by (Gomez and Gomez, 1984) using the (SPSS, 1997) software package. The comparisons among means of the different treatments were carried out, by using the revised L.S.D. test (Al-Rawi and Khalaf-Allah, 1980) at (P>0.05).

RESULTS

Vegetative growth characters

   Results in Table 4 refer to the vegetative growth parameters of potato, as  affected by the ratio between conventional NPK100% fertilization (T1), and TAM® levels (T2 and T3), among in 2017 and 2018 cultivating seasons, under field conditions respectively. During the two cultivating seasons 2017 and 2018, plant height recorded 72.9 cm and 74.73 cm, respectively for the control treatment (NPK100%). On the other hand, it recorded 72.19 cm, and 73.90 cm, after being treated with T2 while recorded 74.39 cm, and 73.65 cm, when treated with T3, during the same cultivating seasons respectively, with no significant difference. In both seasons 2017 and 2018, number of branches recorded 4.83, and 4.50, for T1, 4.66 and 4.83 for T2, and 4.50 and 4.67 for T3, respectively, without any significant difference.

Plant fresh vegetative weight (g) was notably affected by applying TAM® and NPK. In 2017 season, T1 recorded 404.33 g, while it reached its highest record among all treatments in the year 2018 (411.00 g). Significantly, readings differed also between the successive cultivating seasons, where T2 reported 375.00 g in 2017, and 378.00 g in 2018, while T3 record 391.33 g in 2017 and 386.33 g in 2018, respectively.

The dry matter (%) was reported to vary among the two seasons of cultivation (2017 and 2018), where T1 showed 20.31% in 2017, while recorded 20.35% in 2018. Continuously, T2 displayed of 17.81%, and 19.41% for the years 2017, and 2018, respectively, while practicing T5 resulted in 19.68%, and 19.01% for the same successive seasons.

Produced results also demonstrated that tuber weight (g) was 235.30 g, and 223.91 g in 2017 and 2018, respectively, when potato was treated with T1, while it was 260.97 g in 2017, and 264.85 g in 2018, when being treated with T2. At the same time ,T3 gave average tuber weight values of 245.54 g, and 248.70 g, respectively over the two successive seasons 2017, and 2018.

In contrast tuber length (cm), treatment T2 recorded the highest value of 12.47 cm in 2018 and 12.07 cm in 2017, while the lowest value (10.94 cm) was recorded in 2017 season by treatment T1 that valued 11.19 cm in 2018. In the same context, treatment T3 valued 11.73 cm in 2017 and 11.81 cm in 2018 season respectively.

Potato tuber diameter (mm) varied significantly affected by treatments over the two cultivating seasons. In 2017, treatment T1 was found to be 66.65 mm, while it reach 66.14 mm in 2018. T2 gave the heist diameter in 2017 (73.99 mm), and (72.45 mm) in 2018 season, while T3 reached 64.30 mm, and 63.82 mm in both 2017 and 2018 seasons, respectively.

Table 4. Potato vegetative growth parameters as influenced by NPK: TAM^® concentrations among 2017 and 2018 cultivating seasons

*Values followed by the same alphabetical letter(s) in common, within a particular group of means in each character, do not significantly differ, using Revised L.S.D test at 0.05 level of probability.

**T1: NPK100%, T2: NPK50%+TAM2.5 mL L^─1, and T3: NPK50%+TAM5 mL L^─1.

Potato yield parameters

As shown in Table 5, potato yield parameters are presented in Ton fed^-1, as affected by different treatments of NPK and TAM® and their concentrations, among the two successive cultivating seasons, 2017, and 2018. Accordingly, potato tubers’ yield has been categorized depending on size into three groups:

1) Large tubers’ yield, which recorded 6.63 ton fed^-1, and 6.57 ton fed^-1 in 2017, and 2018, respectively, for treatment (T1). On the other hand, it record 8.40 ton fed^-1 in 2017, and 8.36 ton fed^-1 in 2018, for treatment T2, while it recorded 6.74 ton fed^-1 in 2017 and 6.70 ton fed^-1 in 2018, for treatment T3

2) Medium tubers’ yield, was 5.82 ton fed^-1 in 2017, and 5.77 ton fed^-1 in 2018, when potato was treated with NPK Control treatment .7.19 ton fed^-1 and 7.31 ton fed^-1, were the tubers yield  recorded in 2017, and 2018 successive seasons, respectively, when potato was treated by T2, whilst, treatment with T3 gave 7.36 ton fed^-1  in 2017, and 7.17 ton fed^-1in 2018;

3) Small tubers’ yield, was 4.59 ton fed^-1 in 2017, and 4.58 ton fed^-1 in 2018, for treating potato with T1, and 4.16 ton fed^-1 in 2017, and 4.19 ton fed^-1 in 2018, for treating potato with T2, and 4.74 ton fed^-1in 2017, and 4.55 ton fed^-1in 2018, for treating potato with T3, without any  significant differences between treatments.

Finally, the total yield recorded 17.03 ton fed^-1, and 16.92 ton fed^-1 for the successive seasons 2017, and 2018, for T1, 19.75 ton fed^-1  in 2017, and 19.86 ton fed^-1  in 2018, for T2 treatment, and 18.85 ton fed^-1  in 2017, and 18.42 ton fed^-1  in 2018, when applying T3 (Table 5).

Table 5. Potato yield (ton fed^-1) parameters as influenced by NPK:TAM^® concentrations among 2017 and 2018 cultivating seasons.

*Values followed by the same alphabetical letter(s) in common, within a particular group of means in each character, do not significantly differ, using Revised L.S.D test at 0.05 level of probability.

**T1: NPK100%, T2: NPK50%+TAM2.5 mL L^─1, and T3: NPK50%+TAM5 mL L^─1.

Potato leaf N, P, and K mineral content

The content of N, P, and K minerals in potato leaves was determined, as influenced by NPK:TAM® concentrations in 2017 and 2018 cultivating seasons, is represented in Table 3. Leaf-N (mg 100 g^-1 DW) by applying T1 reached 1.93 in 2017, and 2.08 in 2018, while it reached 1.63 and 1.12 when T3 was applied during the two seasons. It also varied significantly to reach 0.95 in 2017 and 0.89 when T3 was applied (Table 6).

Leaf-P (mg 100 g^-1 DW) recorded no significant differences among treatments over the two cultivating seasons. In 2017, treatment with NPK Control resulted in 0.60, while in 2018, it resulted in 0.69. Subsequently, 0.57, and 0.59, were the values obtained by applying T2 in 2017, and 2018 cultivating seasons.

No significant difference was also found when determining potato leaf-K (mg 100 g^-1 DW), which recorded 1.56 in 2017, and 1.54 in 2018, for T1. T2, recorded 1.49, and 1.45, for the same successive seasons, while, T3 recorded 1.52 in 2017, and 1.49 in 2018, respectively.

Table 6. Measurements of potato leaf N, P, and K mineral content as influenced by NPK: TAM® concentrations among 2017 and 2018 cultivating seasons.

*Values followed by the same alphabetical letter(s) in common, within a particular group of means in each character, do not significantly differ, using Revised L.S.D test at 0.05 level of probability.

**T1: NPK100%, T2: NPK50%+TAM2.5 mL L^─1, and T3: NPK50%+TAM5 mL L^─1.

Nutritional quality of potato tubers

The analyses of potato tubers’ nutritional quality, as impacted by applying ratios of NPK:TAM® in 2017 and 2018 cultivating seasons, are shown in Table 5. Significant differences for the percent of total sugar were reported. Total sugar valued 1.42% in 2017, and 1.40% in 2018, when treating potatoes with T1, while higher values of 1.84%, and 1.86%, could be noticed for T2 treatment in 2017, and 2018, respectively, and relatively medium values of 1.62% in 2017, and1.64% in 2018, for T3 were also noticed.

Contrary, Starch content readings displayed no significant differences for treatments over the two cultivating seasons. In 2017, treatment with T1 resulted in 17.55%, and 17.56% for 2017, and 2018, respectively, while treatment T2 resulted in 17.89% in 2017, although the highest value was recorded in 2018 to be 18.83%, at the same time when treatment T3 resulted in 17.84%, and 17.83%, in 2017, and 2018 seasons, repetitively.

Phenol Gallic Acid Equivalents content (mg GAE 100 g^-1), significantly varied between treatments over the two seasons. The highest values were produced by applying T3 in 2018 (1.303), while 2017 recorded 1.268, whilst the lowest values were produced by applying T1 in 2018 (0.542), and 2017 (0.562), whereas T2 recorded relatively medium values of 0.995 in 2017, and 0.976 in 2018 (Table 7).

Table 7. Potato tuber nutritional quality analyses as influenced by NPK:TAM^® concentrations among 2017 and 2018 cultivating seasons.

*Values followed by the same alphabetical letter(s) in common, within a particular group of means in each character, do not significantly differ, using Revised L.S.D test at 0.05 level of probability.

**T1: NPK100%, T2: NPK50%+TAM2.5 mL L^─1, and T3: NPK50%+TAM5 mL L^─1.