Application of inorganic fertilizer NK (18-32) on growth and yield of sweet corn on clay soil

To determine the effectiveness and efficiency of the application of inorganic compound fertilizer NK (18-32) on sweet corn, an experiment was conducted at the experimental garden in Malang, East Java, Indonesia, starting from March to June 2020. The study was arranged in a single-factor RBD with ten treatments and three replications. The treatments were a combination of doses of NK compound fertilizer, a single fertilizer as a comparison, and a control (without fertilizer). Besides control, all treatments were given P fertilizer at a dose of 100 kg/ha. The result showed that doses of 500-750 kg/ha of NK compound fertilizer significantly increased the growth and yield of the sweet corn plant. Each 10 kg dose increase of NK fertilizer will increase the total dry weight of the plant by 1.3055 g and give a yield of 12.57–13.64 tons/ha of fresh cobs. This result is equivalent to the yield of standard N-K single fertilizer (350 kg/ha Urea + 75 kg/ha). The dose of NK compound fertilizer of 125-250 kg/ha was proven to be able to substitute 100% KCl fertilizer (75 kg/ha). The RAE value of 750 kg/ha of NK fertilizer was 105.99 % higher than the standard/comparative single fertilizer. The combination of 125 kg/ha NK fertilizer + 250 kg/ha Urea and 250 kg/ha NK fertilizer + 100 kg/ha Urea, respectively, resulted in a RAE 3.91% and 1.00% higher than the standard fertilizer. Fertilization can improve the quality of sweet corn, namely the level of sweetness increases. NK (18-32) fertilizer doses of 500-750 kg/ha significantly increased the sweetness level of seed corn from 11.17% (without fertilizer) to 15.25-15.25%.


Introduction
The purpose of the study was to determine the effectiveness or efficiency of the inorganic compound fertilizer NK (18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32) for the growth and yield of sweet corn.Considering that fertilization is one of the most frequently used methods by farmers to increase crop productivity in agriculture intensification, Fertilizer is an agro-input component that has a significant effect on plant growth and production.Currently, almost no farmers carry out their farming without fertilization [1].Inorganic fertilizers can be 1230 (2023) 012210 IOP Publishing doi:10.1088/1755-1315/1230/1/012210 2 divided into single-fertilizers and compound fertilizers.A single fertilizer is if it contains only one type of nutrient.For example, urea only contains N, SP-36 as a source of P, and KCl as a source of K. On the other hand, compound fertilizers contain 2 or 3 kinds of macronutrients, and sometimes some micronutrients are added.
In soil, N nutrients are mobile and easy to lose, especially by improper application.Almost all plants in paddy fields and dry land are in dire need of nitrogen fertilizer.About 60 enzymes require the presence of K, with high concentrations of K found at active growth points and in young seeds.About 60 enzymes require the presence of Kalium, with high concentrations of K found at the point of active growth and in young seeds [2].The government's policy of eliminating subsidies for fertilizer prices has resulted in high fertilizer prices and frequent shortages of fertilizers in the market.This condition created an open market mechanism for the procurement and distribution of various types of inorganic and organic fertilizers.There are many types of N, P, and K fertilizers on the market, both local and imported, in single or compound forms.In terms of distribution, storage, and application of NPK compound fertilizers, compound fertilizers are more efficient than single fertilizers.
The research was carried out on dry land at the Experimental Garden of Karangploso Malang, East Java, Indonesia.Assessment Institute for Agriculture Technology East Java (500 m asl).The chemical and physical properties of the soil before the study are shown in Table 2. Note: The analysis was carried out at the Soil Laboratory AIAT East Java, 2020.
Land preparation, planting, plant maintenance, and pest and disease control were carried out in accordance with standard operational procedure for the cultivation of sweet corn.The variety of sweet corn was cultivated as a plant indicator.Parameters observed included chemical properties and soil texture of the research location before the research was carried out.Soil analysis is carried out at the Soil Laboratory in AIAT east java.Plant growth parameters included plant height from the base of the stem to the tip of the highest leaf and stem diameter measured 10 cm from the base of the stem, the observation time was 23 days after planting (DAP), 51 DAP, and 69 DAP before harvest.Observation of plant biomass: crown fresh weight, shoot dry weight, root dry weight, and total dry weight (top + root) taken at harvest.Observations of harvest yields included length, diameter, and weight of cobs in the form of husks and without husks, number of rows per cob, sugar level (Total Soluble Solid), and yield of fresh cobs per hectare.Plant height was calculated from the base of the stem to the last stem segment.Stem diameter was measured with digital vernier calliper on the second segment from the base of the stem.Both variables were observed at the age of 23, 51 and 49 days after planting.The fresh weight of the plant canopy was calculated by weighing the plant crown as soon as possible before the water content in the plant decreased significantly.Canopy or root of plant dry weight was calculated by weighing the plant canopy or root after drying in an oven at 60 0 C for 48 hours.Observation of the length, diameter weight with and without husks and rows number of corn cobs was carried out by measured, weighing or calculated each corn cob sample.Fresh corn yields per hectare were obtained from the conversion of the average weight per treatment plot.
The existence of the treatment effect was concluded through the F value of variance (Anova) at the 5% level.NK fertilization (18-32) had an effect on the observed parameters if the calculated F value was very significant at the 5% level or the Pr > F value was greater than 0.05.The difference between fertilization treatments was concluded by conducting a further test of the mean or average value using the Duncan's Multiple Range Test at a level of 5% (Steel et al., 1993) in [4].
Determining the effectiveness or efficiency of fertilizer inorganic NK (18-32) was approached by calculating the value of Relative Agronomic Effectiveness (RAE).RAE is the ratio between the increase in yield due to the use of a fertilizer with the increase in yield using standard fertilizers multiplied by 100% (Mackay, et al, 1984) in [4].with formula :
The length of the cob fed with fertilizer NK (18-32) 250 kg/ha had the same length as plants with standard treatment but was smaller in diameter.While the fertilizer NK (18-32) 375 kg/ha produces a cob that has the same size, both in diameter and length.This finding indicated that the use of fertilizers NK (18-32) 375 kg/ha and standard single fertilizer were equally good for cob size.The increase in NK fertilizer (18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32) up to 750 kg/ha was not followed by a significant increase in cob size.NK fertilizer (18-32) also had a very significant effect on the length of the cob, and the diameter of the cob, both with and without grain (Table 8).
Fertilization NK (18-32) had a very significant effect on the weight of cobs, both with and without husks; the number of rows per cob; and the yield of fresh cobs per hectare (Table 9).The fertilization treatment significantly increased the sugar content of the seeds compared to the control.The fertilizer dosage NK 500 kg/ha was significantly higher in seed sugar content than the standard single fertilizer dose (Table 9) Therefore, the addition of K from NK fertilizer (18-32) increases the sugar level of sweet corn yields.

Discussion
The land used for the effectiveness test has the chemical and physical properties of the soil before the study with a value of soil pH of 7.4.Generally, the change in soil pH is around six to 7.5 and has very little direct effect on either plant roots or microorganisms (Jiang et al., 2018).The availability of nutrients in the soil solution is strongly influenced by the activity of microorganisms, and the barrier to the activity of microorganisms will inhibit the availability of nutrients for plants [5].
The content of C-organic and nitrogen in the land was moderate, so it is expected to show a good response to the research conducted.Plant growth will benefit from soil of the low medium class.The status of C-Organic and Total Nitrogen was in the medium class, and the levels of exchangeable cations (Ca, Mg, K, and Na) were all high, except for K at moderate levels [6].The results of the study stated that sweet corn fertilization had a significant effect on nitrogen uptake but not on phosphorus or potassium [7] The high content of Ca has the potential to reduce the availability of P in the soil solution due to the occurrence of P fixation with Ca.The cation exchange capacity is high, which means the level of response of the soil to fertilizer will be good.Based on the soil analysis, it can be concluded that, in general, the soil in the study area has moderate fertility [8].. Soil calcium content has the potential to reduce the availability of P because it combines with Al, Fe, Ca, and F and K in the soil and can be a limiting factor for plant growth [9].
Fertilizer treatment NK (18-32) had a very significant effect on plant height at all ages of sweet corn plants.Sweet corn productivity can be increased by using the right fertilizer according to plant needs [10], so that the height of sweet corn plants shows a positive response to fertilizer treatment NK (18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32) given.Increasing the dose to 500 kg/ha significantly increased plant height, but subsequent dose increases up to 750 kg/ha did not increase plant height.The release of nutrients in different media shows the average release of P and K in coarse sand, respectively, is 38% and 24% higher than in clay loam and substantially greater N release (49%) [11].
The decrease in urea and substitution of KCl with NK (18-32) did not have the potential to reduce plant stem diameter in the range of stem diameter as large as the stem diameter of standard single fertilizer treatment.Plant stem diameter showed a positive response to fertilizer treatment NK (1832) produced the same plant size, and the growth of sweet corn with NPK fertilizer and the addition of dolomite was better [12].
There was an increase in the number of leaves in the NK fertilizer treatment (18-32) 750 kg/ha and did not differ from the standard single fertilizer treatment.Urea substitution of as much as 28.57%, 71.43%, and 85% had no significant effect on the number of leaves.The combination of urea with NK (18-32) was not significantly different from the standard single fertilizer.The application of NPK fertilizer absorption of N, P, and K nutrients was highest in sweet corn plants and the highest weight of sweet corn cobs [13].The response of canopy dry weight and total plant weight to NK treatment up to a dose of 750 kg/ha was significantly linear.while the root dry weight showed a response to a quadratic level.The relationship to a linear level between fertilizer doses NK (18-32) with canopy dry weight, root dry weight, and total plant weight is shown in Figure 1.Adding 10 kg of NK (18-32) increases the canopy, root, and total plant weights by 1.0303, 0.2749, and 1.3055 gr, respectively.It means fertilizer NK (18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32) is very effective for increasing plant growth, especially in the upper part of the plant (canopy).The results of the application of NPK fertilizer showed the percentage of nitrogen absorbed by plants increased from 31.1% to 38.7%, compared to a single N treatment [5].
The weight of the cobs in the treatment group was not different from the standard dose of a single fertilizer treatment.It means fertilizer NK (18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)) is more efficient because, in addition to replacing KCl, it also adds N so that it does not reduce the weight per cob even though urea is lowered from the standard dose.The application of liquid organic fertilizer had the highest effect on plant height, leaf area, fresh root weight, the weight of skinned cobs, and the weight of unskinned cobs; and the application of the proportion of potassium significantly increased starch content, soluble sugar content, sucrose content, and sucrose metabolism [14].
The number of fertilization lines NK (18-32) 750 kg/ha was significantly higher in row number per ear compared to standard single fertilization (350 kg/ha Urea + 75 kg/ha KCl + 100 kg/ha SP 36).The reduced urea dose will be followed by a decrease in the number of rows per cob even when combined with increased fertilizer.Fertilizer dosage of urea of 300 and 450 kg/ha in an integrated manner with other fertilizers in an integrated manner is recommended for sweet corn cultivation [1].NK (18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32) and the addition of Urea can increase the number of rows, so fertilizing macro elements with a combination of NPK fertilizer is recommended for increasing corn productivity [15] The application of P and urea composite fertilizers made plant growth higher than the single fertilizer treatment [16].
The fertilization treatment significantly increased the sugar content of the seeds compared to the control.Fertilizer dosage NK (18-32) 500 kg/ha was significantly higher in seed sugar content than the other doses and the standard single fertilizer treatment.When compared to plants only fertilized with NK (18-32) the combination Urea+NK (18-32) did not significantly increase sugar content.The results show that KCl fertilization up to 100 kg/ha and giving cecan charcoal 1 t/ha has not been able to increase the sweetness of sweet corn and the results show that optimal urea application produces a higher harvest index [17].
NPK fertilizer on sweet corn increases the yield of more cobs and forage and affects the quality of protein, sugar, and starch content [18].The combination treatment of NK fertilizer (18-32) with Urea resulted in a weight of fresh cobs ranging from 12.65-13.41t/ha.These results did not differ from the results achieved by the treatment of NK (1832) at 500-750 kg/ha (No. 6-7) and with a single standard dose of fertilizer.Inorganic fertilizers (90 kg N-60 kg P2O5-60 kg K2O) resulted in the highest cob position, reaching 76.83 cm and a cob yield of 11.79 t/h compared to vermicompost fertilizer [8].
This indicates that the use of NK fertilizer (18-32) at 125-375 kg/ha is very efficient as a substitute for KCl.At the same time, the efficiency of using urea fertilizer is reduced to 28-85% of the standard dose.The difference is quite significant in the available soil p and K content in each of the different treatments [19].For optimum production of sweet corn, the dose of inorganic fertilizer must be according to the optimum recommendation [20] and the test results of several varieties of sweet corn with NPK fertilization were able to increase the weight of the cob, the length of the cob, the number of rows and seeds.
Based on the calculation of fertilizer recommendations NK (18-32) at the same SP36 dose (100 kg/ha) for soils with characteristics such as the study site with moderate fertility is 587.26 kg/ha with a potential yield of fresh cobs weighing 13.06 tons/ha, an increase in yield of 8.4% compared to the yield of standard single fertilizer application.Maximum fertilization does not exceed 751.47 kg/ha because it will reduce the yield of fresh cobs.Application of organic vermicompost fertilizer without NPK is not comparable with complete macro element inorganic fertilizer on plant height and cob yield t/ha [22].Fertilizer use NK (18-32) is more efficient because with 1 type of fertilizer it supplies N and K elements at the same time.The results in the field of fertilizer treatment with a maximum dose of 750 kg/ha, visually, there were no symptoms of excess chlorine compounds.The use of fertilizers is more efficient than the use of standard single fertilizer combinations of 350 kg/ha Urea + 75 kg/ha KCl and 100 kg/ha SP 36.A combination of NPK+Mg (250 kg/ha) fertilization has a significant effect on potassium availability, potassium uptake, and yield.sweet corn 8.68 t/ha [23].The combination of NK fertilizer (18-32) resulted in a mass of fresh cob weight which was statistically the same as the yield level of the standard single fertilizer.The application of NPK fertilizer is more effective in influencing sweet corn yield [24].Production and yield components of sweet corn that are cultivated conventionally are significantly higher than those grown organically [25].The RAE value achieved by fertilizer NK (18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32) has met the requirements with the highest RAE value obtained in the fertilizer treatment NK (18-32) at the highest dose of 750 kg/ha, 5.99% more effective than standard single fertilizer use Urea 350 kg/ha + KCl 75 kg/ha + SP 36 100 kg/ha.The application of NPK fertilizer (26:26: 10) and the addition of urea was more economical for maize cultivation with a higher yield of 2.4% [26].Reduction of Urea from 350 kg/ha to 250 kg/ha (equivalent to 40% of standard Urea) combined with fertilizer NK (18-32) 250 kg/ha as a substitute for KCl was 3.91% more effective than standard single fertilizer [9].

Figure 1 .
Figure 1.The relationship between the dose of compound NK fertilizer and the dry weight of shoots, roots and total sweet corn plants in the experimental garden of Karangploso, East Java, AIAT.

Table 2 .
The results of soil analysis at the location before the study at the Karangploso Experimental

Table 4 .
F value count compound fertilizer NK (18-32) on sweet corn plant height and stem diameter

Table 6 .
The calculated F value of NK compound fertilizer (18-32) on the number of leaves and weight of sweet corn plant biomass

Table 7 .
Number of leaves and biomass of NK fertilizer application (18-32) sweet corn plants

Table 8 .
Calculate fertilizer application NK (18-32) on cob weight, cob length, and yield per hectare of

Table 10 .
decreased 2.91% effectiveness.In addition to treatments No. 7, 8, and 9, which have RAE values> 100%, treatments No. 6 and No. 10, with RAE values of 96.28% and 97%, have adequate effectiveness, although still below the effectiveness of standard single fertilizer.Weight of cob with and without grain, number of rows and yield of fresh cob per hectare and RAE value for each fertilizer treatment NK (18-32) sweet corn