Increasing lettuce productivity through Starter Solution Technology (SST)

Starter Solution Technology (SST), which is a highly concentrated liquid fertilizer, has been researched by AVRDC the World Vegetable Center. SST is a technological innovation to reduce fertilizer input while also increasing the efficiency of fertilizer use and crop productivity. The purpose of this research is to apply starter solution technology which is an efficient way of using fertilizer in order to increase lettuce production. The research was conducted in Tawangargo Village, Karangploso District, Malang Regency from July to September 2022. There were 10 treatments, including P1 = NPK 3 gr/plant, T2 = NPK 2 gr/plant, P3 = 1.5 g/plant, P4 = 1 g /plant, P5 = 0.5 g/plant, P6 = NPK 3 g/plant + SST, P2 = NPK 2 gr/plant + SST, P3 = 1.5 g/plant + SST, P4 = 1 g/plant + SST, P5 = 0.5 g/plant + SST. The results showed that the use of SST technology was able to produce better growth and yield and was able to reduce the use of inorganic fertilizers by more than 60% from the current level of fertilizer use without significant reduction in yield. Adding fertilizer to the starter treatment reduced lettuce production.


Introduction
Lettuce is an important dietary vegetable, that is consumed fresh in salads.Lettuce consumption has several health benefits that are associated with the presence of vitamin C, phenolic compounds, and fiber content [1].Lettuce, a low-calorie, low-fat, and low-sodium vegetable, is rich in fiber, folate, and vitamin C, as well as essential minerals such as iron [2].
Based on data provided by Central Bureau of Statistics 2019 [3] lettuce crop production in Indonesia from 2015 to 2018 was 600,200 tons, 601,204 tons, 627,611 tons, and 630,500 tons, respectively.The demand for lettuce in the world market also increased in 2012 by 2,792 tons, and lettuce imports in 2012 were 145 tons [3].Although lettuce production continues to increase, it is still not sufficient.Insufficient production is likely due to low production.The low production of lettuce plants in Indonesia can be caused by several factors, one of the factors that can reduce lettuce productivity is the unmet need for fertilizers, especially nitrogen, so that if nitrogen needs are met properly, it can increase lettuce yields.
Lettuce belongs to plants that respond well to fertilizer [4].When the application of high nitrogen fertilizers will give real advantages to the growth, yield, and quality of lettuce [5].A balanced supply 1253 (2023) 012042 IOP Publishing doi:10.1088/1755-1315/1253/1/012042 2 of nitrogen, phosphorus, and potassium also provides the best lettuce yield and postharvest quality [6], but too high a number of fertilizer applications can also inhibit lettuce growth and yield [7].The notion of lettuce response to various nutrients, such as N, P, and potassium (K), allows us to perfect the use of fertilizers to optimize their performance and nutritional quality.
The addition of KNO3 can increase available nutrients as well as reduce the inhibition of nutrient flow in the growth medium caused by the components of the growth medium [8].The higher the nutrient concentration is basically a picture of the number of charged ions or particles that dissolve in water, with the increasing concentration of the nutrient solution, the faster the electrical conduction in the nutrient solution [9].KNO3 is a macronutrient fertilizer needed for plant growth and is directly involved in physiological processes, including photosynthesis, transpiration, plant growth, and development [10].Previous studies have shown that plant growth and yield are strongly influenced by different amounts of potassium fertilization [11].
The content of the Red KNO3 fertilizer is quite good and friendly to the environment, so it will not change the soil's acidity level, which has the potential to damage the quality of the soil.This Red KNO3 fertilizer can be used on horticultural crops and food crops.The content used by this Red KNO3 fertilizer can be absorbed well by the soil and plants so that it can absorb quickly.In addition, this fertilizer is more easily dissolved in water and does not cause deposits in the soil [12].
Improper application of fertilizers, both type, dosage, time, and method of fertilization used can cause the plant to be disturbed, so that the plant cannot produce as expected [12].The continuous use of artificial fertilizers without returning organic matter can result in the soil becoming saturated with certain nutrients, so that within a certain period of time it will reduce crop yields.Optimal nitrogen application can increase plant growth, increase protein synthesis, chlorophyll formation, which causes leaf color to become greener, increase the ratio of root shoots, improve plant metabolism, carbohydrates, as a result of which plant growth and production increase [13].
From this problem, a solution was found in reducing the use of chemical fertilizers so that they could be optimal when using them, namely the use of SST technology.Starter Solution Technology (SST) is a mixture of chemical fertilizers with water to make young plants grow optimally [14].SST can stimulate plant growth at the time of seeding and is administered around the roots of cultivated plants [15].This technology is also used when transplanting cultivated plants in order to reduce the impact caused by transplanting.This is because when transplanting, there will be disturbances in the growth of cultivated plants, which affect the absorption of nutrients in the soil [16].In addition, later, the nutrients contained in the growing medium will be available when the cultivated plants are young [15].The mechanism for using SST is to apply fertilizer solution directly when planting cultivated plants after being moved from the nursery.Watering is carried out on the holes of seedbed plants of cultivated plants.
SST technology will have a direct impact on young cultivated plants because it can streamline fertilizer needs and also stimulate plant growth to be more optimal [17].SST is an innovative technology to reduce fertilizers, as well as being able to increase fertilization productivity and increase the availability of nutrients for plants, which is beneficial for reducing crop pollution [18].
Good early growth will make plants healthy and promote better growth in later phases, making them more resistant to climate change and pest/disease attacks.The technology was developed by AVRDC (Asian Vegetable Research and Development Centre), which is an international non-profit organization for vegetable development and research [19].AVRDC has disseminated Starter Solution Technology (SST) in several countries, such as Thailand, Taiwan, China, Indonesia, and India [20].The purpose of this study was to determine the influence of the proper use of starter solution (SST) technology on increasing lettuce production (Lactuca sativa var.capitata).

Methodology
The research was conducted in Tawangargo Village, Karangploso District, Malang Regency.The climate at the activity site is tropical with rainfall of 298 mm per year with an average temperature of 18-32°C and humidity of 75-98% [21].The height of the internship site is at 770 MDPL.The time taken to carry out this research is from July to September 2022.
The materials used were lettuce plant seeds used were green curly lettuce commonly grown by local farmers in the study area, polybags measuring 5 kg and NPK Mutiara complex fertilizer as a source of N, P and K were used in this study, and KNO3 fertilizer as a high-concentration starter solution (SST) using red KNO3.The method of its application is poured near the root area simultaneously after the removal of the plant, and at a critical time (one month after planting).
The study was carried out in the form of factorial experiments in a randomized block design (RBD) and there are 10 treatments combinations with 3 replications, including P1 = NPK 3 gr / tan, P2 = NPK 2 gr / tan, P3 = 1.5 g / tan, P4 = 1 g / tan, P5 = 0.5 g / tan, P6 = NPK 3 g / tan + SST, P7 = NPK 2 g / tan + SST, P8 = 1.5 g/tan + SST, P9 = 1 g/tan + SST, P10 = 0.5 g/tan + SST.The SST solution given is by using 1.5 g of KNO3 mixed with 300 ml of water so that each plant gets a starter solution (SST) of 50 ml, which is given when planting.Where all treatments are given organic fertilizer bokashi cow dung with a dose of 5 g / plant obtained from local producers.
Observation begins to be carried out when the plant is 1 week old after planting, The observation parameters carried out include changes in lettuce plant growth, including: Plant Height (cm), Plant canopy length, plant canopy width, and number of leaves.Meanwhile, changes in plant yields include the fresh weight of the plant (g), the dry weight of the plant (g), the dry weight of the plant root (g) and the root shoot ratio.For the dry weight of the plant and the dry weight of the roots of the plant is carried out by pulling out the plant, then the soil attached to the roots is cleaned with water.Furthermore, it is ventilated with a temperature of 70 o C for 2 x 24 hours and then weighed.The observation of the ratio of canopy roots is a comparison between the dry weight of the roots and the canopy of plants that are weighed first and then compared.This observation is carried out 6 MST or at harvest time.The calculation of the ratio value of the root of this header can be obtained using the formula = (Dry weight of the plant root / dry weight of the plant header) [22].All data obtained were analyzed using variance.If there are differences in treatment that have a significant effect (F count > F Table ), then proceed with the 5% level DMRT test.

Results and discussion
Table 1 shows the effect of the combination of SST treatment and NPK fertilizer dose on plant height.From the table, it is shown that plant height growth at the age of 1 week after planting shows that the treatment of giving NPK 1.5 g SST and without SST planting did not have a significant effect when compared to giving NPK 2 g and 3 g.Meanwhile, plant growth given NPK of 0.5 g and 1 g of SST and without SST results in lower growth.
At 2 and 3 weeks after planting, it is seen that the growth of plants with NPK 1.5 g SST yields a high crop, which is no different from giving NPK 2 g SST, 3 g SST, or NPK 3 g without SST.At the age of 4 weeks after planting the plant growth with the giving of NPK 1 g SST produces a high crop that is no different from giving fertilizer NPK 1.5 g SST, 2 g SST and 3 g SST and NPK 3g without SST.This is according to the results of research [23] that shows lettuce plants that get high KNO3 and NPK treatments produce higher crops than lettuce without the fertilizer treatment.Meanwhile, at the end of the observation of plant growth at the age of 5 weeks after planting, it was shown that plant growth with the application of NPK fertilizer of 0.5 g SST was not significantly different from plants treated with NPK fertilizer of 1 g SST, 1.5 g SST, 2 g SST, and 3 g SST and NPK 3g without SST.
Inorganic fertilizers are able to increase the growth and yield of vegetables because they help provide nitrogen and fertilizers containing potassium.Nitrogen plays a role in making amino acids, proteins, and enzymes; it is the main component of chlorophyll, so it is very important in the process of photosynthesis; it is also an important part of some vitamins and improves the quality and production of vegetables [24].
Potassium functions to activate enzymes, plays a role in photosynthesis, protein formation, and sugar transport.In addition, potassium plays an important role in the process of opening and closing stomata, as well as improving the quality of fruits and vegetables.A high concentration of K is able to improve the physical quality, disease resistance, and shelf life of fruits and vegetables.The use of KNO3 fertilizer can increase the concentration of P and K in lettuce plant tissues [25].

Table 1. Effect of the combination of SST treatment and NPK fertilizer dose on plant height (PH).
Notes: Nominals that are accompanied by a similar character in the same column show no significant difference based on the LSD test at a 5% trust level.LSD= Least Significant Difference; CV= Coefficient Variance, PH 1 = plant height 1 week after planting, PH 2 = plant height 2 weeks after planting, PH 3 = plant height 3 weeks after planting, PH 4 = plant height 4 weeks after planting.PH 5 = plant height 5 weeks after planting.
Table 2 shows the effect of the combination of SST treatment and NPK fertilizer dose on plant canopy length.From the table, it is shown that the length of the plant canopy at 1 week after planting shows that the treatment of giving NPK 0.5 g SST is not significantly different from the length of the plant canopy produced by plants treated with 1 g SST, 1.5 g SST, 2 g SST, and 2 g without SST and 3 g without SST planting.When the plant is 2 weeks old after planting, there is no noticeable difference between giving NPK 1.5 g + SST, giving NPK 2 g + SST, and giving NPK 3 g + SST, compared with giving NPK 1.5 g without SST and 3 g without SST.
At 4 and 5 weeks after planting, it was shown that the treatment with 1.5 g SST resulted in a long plant canopy that was no different from the administration of NPK 2 g SST, 3 g SST, and NPK 3 g without SST.A longer plant canopy provides an opportunity for plants to utilize sunlight more optimally in the process of photosynthesis, ensuring that the life needs of lettuce plants are met.Notes: Nominals that are accompanied by a similar character in the same column show no significant difference based on the LSD test at a5% trust level.LSD= Least Significant Difference; CV= Coefficient Variance, CL1 = canopy length 1 week after planting, CL 2 = canopy length 2 weeks after planting, CL 3 = canopy length 3 weeks after planting, CL 4 = canopy length 4 weeks after planting.CL 5 = canopy length 5 weeks after planting.
Table 3 shows the effect of the combination of SST treatment and NPK fertilizer dose on the width of the plant canopy.From the table, it is shown that the width of the plant canopy at 1 and 2 weeks after planting shows that the treatment of giving NPK 1 g SST is not significantly different from the width of the plant canopy produced by plants treated with 1.5 g SST, 2 g SST, 3 g SST and 1.5 g without SST, 2 g without SST and 3 g without SST planting.When the plants are 3 weeks old after planting, there is no noticeable difference between giving NPK 1.5 g + SST and giving NPK 2 g + SST and NPK 3 g + SST with giving 3 g without SST.At the end of the growth age of 4 and 5 weeks after planting, it was shown that the treatments ranging from 0.5 g NPK + SST to 3 g NPK + SST resulted in a plant canopy width that was no different from treatments ranging from 1.5 g NPK without SST to 3 g NPK without SST.This is because the starter solution has a significant effect on lettuce plant growth [23].This is because a small amount of concentrated liquid fertilizer applied as a starting solution and applied to the soil around the root rhizosphere causes an increase in the concentration of nutrients in the soil solution and makes the nutrients available to plants [26].Root development is further enhanced with a starter solution so that it is able to produce strong and healthy plant growth.Where this is able to display good initial growth and have a significant effect on subsequent growth.Notes: Nominals that are accompanied by a similar character in the same column show no significant difference based on the LSD test at a 5% trust level.LSD= Least Significant Difference; CV= Coefficient Variance, WC 1 = width of the plant canopy 1 week after planting, WC 2 = width of the plant canopy 2 weeks after planting, WC 3 = width of the plant canopy 3 weeks after planting, WC 4 = width of the plant canopy 4 weeks after planting.WC 5 = width of the plant canopy 5 weeks after planting.
Table 4 shows the effect of the combination of SST treatment and NPK fertilizer dose on the number of plant leaves.From the table, it is shown that the number of leaves at 1 week after planting shows that the treatment of giving NPK 0.5 g SST produces the highest number of leaves compared to other IOP Publishing doi:10.1088/1755-1315/1253/1/0120426 treatments.Treatment without an SST booster using KNO3 solution resulted in a low leaf count; this is related to the results of research [9] which showed that potassium reduction in nutrient solution inhibits plant growth and photosynthesis in three varieties of lettuce plants.
Up to 5 weeks after planting, the treatment of 0.5 g NPK + SST produces a high number of leaves and is markedly no different from the treatment of NPK fertilizer application (1 g + SST 1.5 g + SST 2 g + SST is no different from plants treated with 1 g + SST, 1.5 plants produced plants treated with 1.5 g SST 2 SS, 3 g SST and 1.5 g without SST, 2 g without SST and 3 g without SST.This is inversely proportional to the study [27] which states that the addition of concentration from 2% to 8% concentration KNO3 is able to increase the number of leaves, this is related to the way the application of KNO3 dissolved as a booster at the beginning of planting is able to reduce the need for NPK needed so that by adding 0.5 g NPK produces a number of leaves that does not differ markedly with the addition of 3 g NPK accompanied by the application of SST KNO3 solution.It deals the absorption of nutrients by plants; economic efficiency (i.e., by reducing nutrient inputs to optimize agricultural income) and environmental efficiency (i.e., minimizing nutrients to reduce environmental losses) can all be improved with balanced plant nutrition [28,29].Notes: Nominals that are accompanied by a similar character in the same column show no significant difference based on the LSD test at a 5% trust level.LSD= Least Significant Difference; CV= Coefficient Variance.
Table 5 shows the effect of the combination of SST treatment and NPK fertilizer dose on the wet weight of each plant, the dry weight of each plant, the dry weight of the roots of each plant, and the ratio of roots and canopy of plants.The high fresh weight and high dry weight of the plant compared to other treatments were shown in the NPK treatment of 1 g + SST no different from the treatments of 2 g + SST and 3 g + SST.Thus, giving NPK 1 g + SST is already able to produce a high crop weight, no different from giving NPK 3 g + SST.This is because the application of a starter solution with a high enough K content can be absorbed by plants to increase the starch content, which in turn stimulates the growth of new leaves.In addition, K can also increase the photosynthesis efficiency and turgor pressure of plants [30].
So that with the addition of SST and NPK solutions of 1 g can be optimally absorbed by lettuce plant tissue [31].It is also stated that there is an increase in plant biomass of 31-160% with the application of a starter solution directly to the root system around the rhizosphere, which is also triggered by the activity of microorganisms.The application of SST is able to increase the early growth of plants, better early growth of plants so that it can lead to higher crop yields during early harvest.However, it needs treatment around dense soil essential to maintain the booster as an influence of liquid supplements into until the production process results.
The dry weight of plant roots in the NPK treatment of 2 g + SST was able to produce the highest dry weight of the roots compared to other treatments.At the level below is the treatment of giving NPK 3 g + SST.Thus, it can be seen that the dose to produce the optimal root dry weight at the NPK treatment of 2 g + SST featuring the dry weight of the roots is higher than that of the NPK treatment of 3 g + SST.This is in accordance with the results of research [32] that the level of application of nutrients that is too low or too high will result in inhibition of plant growth and development.
Rootshoot ratio shows the root:header ratio is obtained by comparing the dry weight of the root and the dry weight of the header [22].If the root development is more active than the heading development, a large root: header ratio value will be obtained [32].The root header ratio is a character that can be used to indicate excess or deficiency in plants.

Conclusion
The results showed that the use of SST technology in KNO3 solution was able to produce better growth and results and was able to reduce the use of inorganic fertilizers by more than 60% of the current level of fertilizer use resulting in better growth and yields.By adding a bosster starter solution using KNO3 solution at the beginning of growth is able to produce good initial growth as a basis for plants to become stronger adult plants resulting in better growth, so that the reduction in the dose of NPK fertilizer in the next growth can be reduced to more than 60% still results in better growth and does not reduce the yield obtained.

Table 2 .
Effect of the combination of SST treatment and NPK fertilizer dose on plant canopy length.

Table 3 .
Effect of the combination of SST treatment and NPK fertilizer dose on the width of the plant canopy (WC).

Table 4 .
Effect of the combination of SST treatment and NPK fertilizer dose on the number of leaves (NL).

Table 5 .
Effect of the combination of SST treatment and NPK fertilizer dose on plant wet weight, plant dry weight and root dry weight.