Cob and seed characteristics of maize due to nutrient omission techniques

A deficient supply of both macro- and micro-nutrients (minus one test) will respond negatively to the generative characteristics (cobs and seeds) of the maize plant. The aims of this study were (1) to determine the impact of nutrient omission techniques fertilization on the cob and seed developments of maize plants, and (2) to investigate the relationship between the characteristics of maize cob and seed. This study was conducted in a farmers’ field, Medan Selayang, North Sumatra, Indonesia from May to September 2023. A single-factor Randomized Block Design was selected with three replications, namely the elimination of both macro (N, P, K, Ca, Mg, S) and micro (Mn, Zn, Fe, Cu) nutrients. Data were analyzed by ANOVA and followed by DMRT at P<0.05 as well as Pearson correlation. The results indicated that among the nutrient omission techniques fertilization, the absence of nitrogen significantly inhibited the highest seed development was 12.61 to 30.48% followed by not fertilizing manganese ranging from 8.45 to 28.72%. Cob and woody ring diameters were positively correlated and significantly increased embryo length, crown width, and seed length of the maize.


Introduction
Macro and micronutrients are required to promote the growth and yield of maize plants.[1] reported that maize grain yield decreased by 3; 7.7; and 21.9% when reducing the recommended dose of N fertilizer by 25, 50, and 100% from 300 kg ha -1 .[2] found that P2O5 fertilization up to a dose of 31 kg fad -1 significantly increased chlorophyll, leaf area index, and seed yield per plant in hybrid maize by 9.49; 32.11; and 25.43% respectively compared to the control.[3] noted that K nutrient play a role in increasing plant biomass and yield.[4] also found that the application of Mg nutrient increased seed production, 100-seed weight, oil and protein contents, and nutrient uptake in maize plants.[5] stated that leaf Ca levels were positively correlated (0.49 * ) with flowering and grain yield in nine varieties of maize plants.[6] added that the sulphur application dose of 50 kg ha -1 significantly increased the number of grains, 1000-seed weight, and maize yield by 42% compared to the control.
Moreover, micronutrients such as Mn, Zn, Fe, and Cu are also required to increase the biomass and yield of maize plants.[7] noted that the uptake of Mn and Fe was two-thirds earlier in the reproductive stage than Zn.Zn-uptake of more than 70% occurred slightly longer in both vegetative (V) and early reproductive (G) growth.The uptake of Fe had two critical accumulation periods, between V10-V14 (10-14 leafing phase) and post-R4 (doughy-consistency phase), while the Mn-uptake was more incremental with maximum uptake occurring from V10-R4.[8] reported that there was an increase in maize grain yield ranging from 13.5 to 14.6% in the application of Fe fertilizer at a dose of 0.22 kg ha -1 during the V6-R2 phases.[9] also added that there was an increase in maize grain yield of about 18% with the implementation of Zn fertilizer at a dose of 1.0-1.5 kg ha -1 .
The continuous use of land for crop cultivation activities can lead to a decrease in land productivity and maize yield.However, to identify the limiting factor of an important nutrient for plants, biological testing is required through nutrient omission techniques.According to [10], biological testing through the nutrient omission techniques method uses the concept of plant growth responding to the most limiting nutrients.The response is manifested as a decrease in plant height, number of tillers, delayed maturity, smaller seeds, and chlorosis or necrosis.Studies on nutrient-limiting factors in maize plants are limited in scientific reports.[11] found that the limiting factor for the vegetative growth of maize plants was the absence of nitrogen fertilization.[12] added that the highest percentage of limiting factors for maize plants sequentially found without fertilization, P+K; N+K; and N+P were 6.31-105.89;7.73-87.01;38.03-99.70;and 73.78-113.22%respectively, compared to N+P+K.Based on previous studies, the nutrient omission techniques have been implemented on the main macro-nutrients (N, P, K) at the vegetative growth of maize plants and it has never been reported on other macro-nutrients (Ca, Mg, S) and micro-nutrients until the reproductive stage.The goals of this study were (1) to obtain the effects of nutrient omission techniques fertilization (nutrient removal of N, P, K, Ca, Mg, S, Mn, Zn, Fe, Cu) on the cob and seed developments of maize plants, as well as (2) to investigate the correlation between cob and seed characteristics.

Seed source and nutrient omission techniques fertilization
The maize seeds in this study used the superior variety of BISI 79.The maize seeds were planted in a farmer's field, Medan Selayang, North Sumatra, Indonesia at a coordinate of 3°33.669'N and 98°38.832'E from May to September 2023.The growing medium used was topsoil and filled into 20 kg polybags.This study used a single-factor Randomized Group Design, namely the elimination of one macro and micronutrients, which were N, P, K, Ca, Mg, S, Mn, Zn, Fe, and Cu.Fertilizer treatments refer to the nutrient requirements of maize plants [13] then converted to the growing medium (Table 1) and applied by immersing and separating between the nutrients at the beginning of the vegetative and generative phases.The planting spacing was 70 cm × 30 cm and was repeated three replications.Basic fertilization, namely NPK Mutiara was also applied at a dose of 150 kg ha -1 before planting.

Fertilizer treatments
Single fertilizer

Plant management and data collection-analysis
Sprayed with 25 g L -1 deltamethrin and 80% mancozeb according to recommendations and depending on field conditions.The criteria for harvesting was brown maize husk up to 80%.Five seeds were collected randomly from the middle of the maize cobs.The characteristics of maize cob and seed such as cob, pith, and woody ring diameter, embryo length, crown width, pedicel length, seed length, and seed thickness were measured using calipers, while seed weight was measured using an analytical scale.Data were analyzed by ANOVA and followed by DMRT at P<0.05 and Pearson correlation through IBM SPSS Statistic.

Cob and seed characteristics of maize plants
Nutrient omission techniques fertilization significantly affected maize seed characteristics such as embryo length, crown width, seed length and weight (Table 2), but it had insignificant effects on pedicel length, seed thickness, and all cob characteristics (cob, pith, and woody ring diameter).Among all nutrient omission techniques fertilization, P2 (un-fertilizer of nitrogen) showed the highest inhibition of maize seed characteristics such as embryo length, crown width, seed length and weight by 14.71; 18.85; 12.61; and 30.48%, respectively compared to completely fertilized.Likewise, P8 (un-fertilizer of manganese) resulted in the second lower embryo length, crown width, seed length and weight than P2 with inhibition values of 8.45; 18.56; 9.15; and 28.72%, respectively.The significance of maize seed size inhibition due to P2 and P8 treatments is visually smaller as shown in Figure 1.However, P6 (unfertilizer of magnesium) extended the embryo of maize seeds compared to complete fertilization and control.Although the effect was not significant, all nutrient omission techniques fertilization showed lower pedicel length but produced greater pith and woody ring diameter compared to the control.In contrast, the highest seed thickness and cob diameter were found in P4 (un-fertilizer of potassium) at 5.888 mm and 26.32 mm.

Correlation value
The correlation between cob and seed characteristics of maize due to nutrient omission techniques fertilization is presented in Table 3. Maize cob diameter was highly significant and positively correlated to embryo and seed length (0.469 ** and 0.456 ** ).Likewise, woody ring diameter was significant and positively correlated to embryo length, crown width, and seed length (0.399 * ; 0.334 * ; and 0.348 ** ).It was indicated that cob characteristics such as cob and woody ring diameter can improve maize seed development.Maize seed development was significantly affected by nutrient omission techniques fertilization, especially an un-fertilizer of nitrogen and manganese.It was observed in the characteristics of embryo length, crown width, seed length and weight at P2 and P8 treatments (-N and -Mn) which were lower than the complete fertilization.There was an inhibition of seed development of maize plants due to the absence of nitrogen and manganese fertilization was 12.61-30.48%and 8.45-28.72%respectively compared to complete fertilization (Table 2).The inhibition of maize seed development due to the absence of nitrogen and manganese fertilizers will affect physiological processes, especially nutrient uptake and chlorophyll content in the production of biomass and seeds.This finding is supported by [12] that nitrogen uptake was lower, which inhibited leaf area and biomass of maize plants in the absence of N fertilizer compared to phosphorus and potassium.[14] explained that nitrogen plays an important role in seed formation through photosynthesis and the reduction of nitrogen nutrient negatively affects the photosynthetic performance of maize plants.[15] also reported that an un-fertilizer of nitrogen significantly inhibited leaf area, biomass, chlorophyll content, and seed weight per plant of maize.
Likewise, micro-nutrients, especially manganese, play an important role in the photosynthetic process in photosystem II or PSII [16].[17] found that Mn deficiency caused a decrease in net photosynthesis in leaf tissue and PSII quantum products.[18] revealed that Mn deficiency significantly inhibited chlorophyll content, rubisco enzyme activity, and photophosphorylation rate in maize plants.[19] added that maize plants with an un-fertilizer of manganese significantly inhibited chlorophyll content, shoot dry weight, and leaf area.[20] also found that Mn deficiency is also closely related to a decrease in total nitrogen contents in the shoot and root of maize plants.The inhibition of the physiological process of maize plants due to nutrient omission techniques fertilization affected biomass and had an impact on the process of cob and seed development.The relationship between Mn deficiency and N was very evident in this study, with smaller seed size compared to nutrient omission techniques fertilization (Figure 1), although it had an insignificant effect on maize cob characteristics (Table 2).This finding is also confirmed by [21] that the potassium, nitrogen, magnesium, zinc, phosphorus, calcium, and iron nutrients along with dry weight have a slight effect on maize cobs.This researcher also added that the effect of nitrogen nutrient can be considered a major influence on the formation of maize seeds because it can increase the results of photosynthesis and have an impact on the storage of dry matter in the seeds.
However, the size of the maize cob will affect seed size due to nutrient omission techniques fertilization.It is evident from the correlation analysis that cob and woody ring diameter significantly and positively correlated to an increase in embryo length (0.469 ** ; 0.399 * ) and seed length (0.456 ** ; 0.348 * ).Likewise, the woody ring diameter significantly increased the crown width of maize seeds (0.334 * ).Furthermore, pith diameter was only positively but insignificantly correlated with maize seed development.It indicated that the role of cob characteristics also affects the development of maize seeds.This finding is also confirmed by [22] that the diameter, length, and weight of maize cobs were positively and significantly correlated to seed yield per plant.[23] found that cob length was positively and significantly correlated (0.43 ** ) to maize seed yield per plant.[24] also added that maize cob length was positively correlated (0.72 ** ) to the number of seeds.

Conclusions
Nutrient omission techniques fertilization, especially nitrogen and manganese nutrients significantly inhibited maize seed development such as embryo length, crown width, seed length and weight.The inhibition of seed development due to an un-fertilizer of nitrogen was higher at 12.61-30.48%compared to the un-fertilizer of manganese by 8.45-28.72%.It was confirmed that cob and woody ring diameters were positively and significantly correlated to increased embryo length, crown width, and seed length due to nutrient omission techniques fertilization.

References [1]
Su W, Ahmad S, Ahmad I and Han Q 2020 Nitrogen fertilization affects maize grain yield through regulating nitrogen uptake, radiation and water use efficiency, photosynthesis and root

Table 2 .
Size characteristics of maize cobs and seeds due to nutrient omission techniques fertilization.Note: average followed by different letters in the respective columns are significant at DMRT at P<0.05.ns= insignificant effect.

Table 3 .
Correlation values between cob and seed characteristics of maize due to nutrient omission techniques fertilization.