The use of natural minerals compound fertilizers for the production of sweet corn

The natural mineral of polyhalite, which consists of potassium, sulphur, magnesium, and calcium, has the potential to be to supply various essential nutrients to complete the plant’s nutrient requirement, such as sweet corn. The aim of this study to determine the effect of multiple doses of K-Ca-Mg-S fertilizer on sweet corn plants. This research was conducted at Medan City, North Sumatra, with a height of ± 25 meters above sea level from March to May 2023. This study used a Non-Factorial Randomized Block Design with 5 replications and 5 treatments consisting of the dose of fertilizer, namely 0; 2.14, 4.28, 6.42, and 8.57 g/plant. The results of the study showed that several doses of K-Ca-Mg-S compound fertilizer were able to accelerate the male flowering age, which was 53.8 days after planting (dap), the female flowering age was 57.4 dap, and was able to increase the weight of husked cobs, namely 157.758 kg, and seed sugar content of 15.6 % Brix, but did not increase the harvest index.


Introduction
Sweet corn or Zea mays saccharata Sturt is a type of horticultural plant with many nutrients, so it is in great demand in various circles.The nutritional content of corn is almost comparable to rice.Many people prefer sweet corn because, in addition to having a sweeter taste and more fragrant aroma, sweet corn is also rich in sugar content and high calories [1].The sweet corn demand spurred farmers to increase sweet corn production.Therefore, efforts that need to be made to increase the national production of sweet corn plants are to use compound fertilizers for maximum results, especially natural mineral compound fertilizers or polyhalite.
Polyhalite mineral consisting essential macro elements for plant's nutrient.Polyhalite considers as a compound fertilizer containing 14% K2O, 6% MgO, 18% S and 17% CaO.Magnesium (Mg) nutrient is one of the nutrients needed by plants for various metabolic activities.Mg is the only metal ion present in the chlorophyll molecule and forms the chlorophyll nucleus.Many enzymes involved in carbohydrate metabolism require Mg as an activator [2].The benefits of applying K-Ca-Mg-S compound fertilizer to sweet corn plants are that potassium functions in sugar and starch formation, sugar translocation, enzyme activity, and stomatal movement [3].Calcium regulates growth, especially at plant growing points such as young shoots and root tips [4].Magnesium is needed to form green leaves (chlorophyll) and as a co-factor in almost all enzymes in plant metabolic processes such as photosynthesis and cell formation [5].Sulfur functions in spurring plant growth, one of which is the number of leaves [6].
In the cultivation of corn plants, the thing that must be taken care of fertilization.The availability of nutrients in the soil that plants will utilize for growth and development increased by fertilization.As is known, fertilizers are divided into two types, namely organic and inorganic fertilizers [7].This IOP Publishing doi:10.1088/1755-1315/1302/1/012021 2 study aims to determine the effect of natural compound mineral fertilizers on sweet corn production.

. Research Study and Materials
This study was conducted on Jalan Harmonika Padang Bulan Selayang II, Medan Selayang District, Medan, North Sumatra, with ± 25 meters altituded from sea level.At the coordinate point 3°33'118.4"N98°38'45.5"E.This research was carried out from March to May 2023.
The tools used in this study are hoes to clear land and cultivate land, meters to measure land area and plant height, scales to weight crop production, trace samples for markers of plants that are sampled, hand refractometer brix sugar 0-32% to measure sugar levels of corn kernels, cameras to take documentation during research, and stationery to take research data.
The materials were sweet corn seeds of Bonanza F1 variety as planting material, natural mineral compound fertilizer K-Ca-Mg-S (polyhalite) with a composition of 14% K, 17% Ca, 6% Mg and 19% S as fertilization material, soil as a planting medium, polybag size 10 kg (45 cm x 22.5 cm in a folded state) as a container for planting media, water for watering plants, insecticides to control pests, fungicides to suppress diseases in plants.

Methods
This research used a Non-Factorial Group Randomized Design with 5 treatments consisting of fertilizer doses given, namely: P0= 0 g/polybag, P1= 2.14 g/polybag or 107.125 kg/ha, P2= 4.28 g/polybag or 214.25 kg/ha, P3= 6.42 g/polybag or 321.375 kg/ha, P4= 8.57 g/polybag or 428.5 kg/ha (1 plant per polybag).The land is cleared first of weeds, plant root residues, and rocks using a hoe, then leveled and formed a plot of 25 plots, which consist of 5 rows (repetitions), with each row consisting of 5 plots.
The growing media was prepared by enter the soil into a 10 kg polybag.In each polybag that has been prepared, planting holes are made by cutting off 3-5 cm deep.Each hole is planted with two seeds of sweet corn and then closed again.Watering is carried out two times (morning and evening), adapted to field conditions.If it does not rain one day before, watering will be done.Weeding weeds is done manually by pulling weeds that grow in the polybag and plot area and around the plot with hands and hoes.This reduces competition between main crops and weeds to get water and elements from the soil.Applications K-Ca-Mg-S fertilization is applied and dose according to the treatment on the exact planting day.Control is carried out depending on the field's level of pest and disease attack.Pests that attack plants are armyworm pests (Spodoptera frugiperda J.E. Smith).Pest control is carried out by chemical control using insecticides made from active ingredients BPMC (phenobukarb) 500 g / l.The disease that attacks sweet corn plants is late blight (Helminthosporium turcicum).Control is carried out by spraying plants using fungicides made from active ingredients Mancozeb 80%.Harvesting sweet corn of the Bonanza F1 variety can be done in the milk ripening phase when the seeds are tender enough to be pierced, and the juice looks milky.Parameters to study were flowering age of males and females (days), weight of the cobs (g), Harvest Index and, seed sugar content (% Brix).Harvest Index is the ratio of the weight of the part of economic value to the entire biological weight of the plant.

Flowering age of males
The average flowering age of males and females of plants on the application of K-Ca-Mg-S fertilizer doses showed in Table 1.Table 1 showed that the most extended average flowering age of males is found in the administration of fertilizer doses of 0 g (P0), which is 55.65 days after planting (dap), and the fastest in the application of fertilizer doses of 4.28 g (P2) with an average of 53.80 dap. Figure 1 shows that the relationship between fertilizer doses and males flowering age of sweet corn forms a minimum quadratic curve.

Flowering age of females
Table 1, presented that the most extended flowering age of females is found in the administration of 0 g (P0) fertilizer dose, which is 59.35 dap, and the fastest in the application of 4.28 g (P2) fertilizer dose with an average of 57.40 dap.The relationship between fertilizer dose and flowering age of females is presented in Figure 2. The relationship between fertilizer dose and flowering age of females is presented in Figure 2.

Weight of the cobs
The average weight of cobs on the application of several doses of K-Ca-Mg-S fertilizer was showed in Table 2.  2 presented that the highest average weight of cobs is found in the administration of a fertilizer dose of 4.28g g (P2), which is 157.76 g, and the lowest average is found in the application of a fertilizer dose of 0 g (P1) which is 130.93 g.The relationship between fertilizer and the weight of cobs is presented in Figure 3.

Harvest Index
The average harvest index on the application of several doses of K-Ca-Mg-S fertilizer showed in Table 3.According Table 3, the highest average harvest index is found in the administration of fertilizer doses of 4.28g g (P2), which is 0.2647, and the lowest average is found in the administration of fertilizer doses of 0 g (P1) and 8.57 g (P4) which is 0.2490.

Seed sugar content
The average sugar content of sweet corn kernels in applying several doses of K-Ca-Mg-S fertilizer in Table 4.   4 showed that the highest average seed sugar content is found in the administration of a fertilizer dose of 4.28g g (P2), which is 15.60 g.The lowest average is found in administering a fertilizer dose of 0 g (P1), which is 13.25 g.The relationship between fertilizer dose and weight of cob is presented in Figure 4.This result corresponds to the opinion stating that proper application of fertilizer dosage will give good results for plant growth and production.Fertilizer application only sometimes provides effective results because it is influenced by many factors, including the correct dose, method, and time of application [8].This shows that the compound fertilizer content of K-Ca-Mg-S can respond to the age of male and female flowering in sweet corn plants.
The K-Ca-Mg-S compound fertilizer doses made a significantly on cob weight.The calcium element content in compound fertilizer affects the metabolic process of plant growth and production quality [9].The cob is influenced by the weight of the seeds in the cob.The increase in seed weight is closely related to the amount of photosynthetic partitioned into the cob.
The harvest index value obtained has no real effect on the index value in other treatments.The value of the harvest index is obtained by the economic weight produced against the biological weight.The lowest index value was found in the treatment with the highest fertilizer dose of 8.57 g/polybag, which was 0.2490.Proper application of fertilizer dosage will give good results for plant growth and production.Fertilizer application only sometimes provides effective results because it is influenced by many factors, including the correct dose, method, and time of application [7].
Sweet corn kernels' highest observed sugar content was found at a dose of 4.28 g.The K-Ca-Mg-S compound fertilizer contains potassium nutrients that function in sugar and starch formation.Potassium, although playing an essential role in plant growth, especially during the maturation period of plants, can affect photosynthesis in the formation of chlorophyll, seed filling and is essential in the formation of carbohydrates [10].It is proven in this study that the application of 4.28 g / polybag K-Ca-Mg-S compound fertilizer produces the highest seed sugar content.Sulfur (S) is an essential constituent of various proteins, vitamins, and some plant hormones.This element plays a role in protein and amino acid synthesis, carbohydrate metabolism, and chlorophyll production [11].

Conclusion
The application of K-Ca-Mg-S fertilizer was able to accelerate the flowering age of males at 53.8 dap, the flowering age of females at 57.4 dap, increase the weight of cob clusters at 157.758 kg, and seed sugar content by 15.6 % Brix, but could not increase the harvest index.Based on the results of this study, to get good sweet corn crop production results, it is recommended to apply compound fertilizer K-Ca-Mg-S at a dose of 4.28 g /plant.

Figure 2 .
Figure 2. Relationship between flowering age of females and dose of K-Ca-Mg-S compound fertilizer

Figure 4 .
Figure 4.The relationship between seed sugar content and K-Ca-Mg-S compound fertilizer dose

Table 3 .
Sweet corn harvest index on multiple doses of K-Ca-Mg-S fertilizer