The effect of humates on the vitality, morphogenesis, and yield of stubble corn

One of the reserves for obtaining feed for livestock is stubble crops of corn. The climatic conditions of the Steppe of Ukraine (the duration of the frost-free post-harvest period, sufficient temperature, and naturally decreasing day length) favor the growth and development of corn in stubble crops. The limiting factor for the growth and development of stubble corn is the lack of moisture in the second half of summer. Therefore, to obtain high and stable yields, stubble corn must be cultivated under irrigation.

The economic value of the stubble corn yield significantly increases if the plants form cobs, thereby increasing the collection of feed units per hectare. Therefore, all agrotechnical measures should be aimed at accelerating the development of stubble corn. The issues of accelerating plant development are not only of practical importance but also of theoretical interest, as uncovering the patterns of this process can, in turn, open new ways to manage it. A number of researchers have established the stimulating effect of humic acids on plants. Based on this, we set ourselves the task of accelerating the development of stubble corn, increasing its yield, and improving its quality by applying fertilizations with potassium humate in combination with mineral fertilizers.

Research Objectives:

1. Determine the influence of humic and fulvic acids on the biochemical processes of stubble corn.
2. Study the effect of humic and fulvic acids on the morphogenesis of reproductive organs.
3. Determine the effectiveness of fertilizations with ammonium nitrate, superphosphate, and potassium humate on the yield of stubble corn.

Experimental Design:

1. Control.
2. Root fertilization with N20, P20 (background).
3. Background + potassium humate 2 l/ha (root fertilization).
4. Background + potassium humate 0.003% (foliar fertilization).

THE EFFECT OF POTASSIUM HUMATE ON THE BIOCHEMICAL PROCESSES OF STUBBLE CORN

Plants in their development pass through a series of successively changing stages. For each stage of plant development as a whole and for each individual stage of the formation of reproductive organs, a specific metabolism is characteristic. Therefore, in our research, sampling for biochemical analyses was timed to critical moments in the development of the reproductive organs of stubble corn, namely to the period of tassel differentiation, flower formation in the tassel, differentiation of spikelet scales in the cob, and the tasseling phase. The analyses included primordial and formed tassels, cobs, and the top two leaves.

Changes in the Activity of Respiratory Enzymes in Stubble Corn Under the Influence of Potassium Humate

It is known that the intensity of respiration is closely related to the activity of respiratory enzymes. Therefore, at individual stages of organogenesis, we determined the activity of catalase and peroxidase in the vegetative and reproductive organs of stubble corn (Table 1).

Table 1. The Effect of Mineral Fertilizers and Potassium Humate on the Activity of Respiratory Enzymes in Stubble Corn

Plant Organs	Control		Root Fertilization N20, P20		Background + Potassium Humate 2 l/ha		Background + Potassium Humate 0.003%
	Catalase	Peroxidase	Catalase	Peroxidase	Catalase	Peroxidase	Catalase	Peroxidase
9-Leaf Phase
Tassel	4	70	10	70	10	85	-	-
Leaf	13	65	26	53	29	81	-	-
13-Leaf Phase
Tassel	33	35	34	22.5	38	28	35	35
Cob	14	22.5	20	35	24	43	16	35
Leaf	9	32.5	10	40.5	14.5	32.5	19.5	32.5
Tasseling Phase
Tassel	35.0	24.0	38.5	24.0	24.0	35	33.5	31.5
Cob	9.0	19.0	12.0	19.0	11.5	22.5	11.5	19.0
Leaf	24.0	43.0	21.0	35.0	17.0	43.0	15.5	28.0

Note: Catalase activity — in ml O₂ per 1 g of sample in 15 min., peroxidase — in mg Co per 1 g of sample.

The table shows that during the ontogenesis of stubble corn, there is some increase in catalase activity in the tassel and leaves. However, peroxidase activity in them decreases with the age of the plant, which is associated with leaf aging. During cob formation in stubble corn, a gradual decrease in the activity of both catalase and peroxidase is observed. It is possible that at later stages of cob development, there is a change in the specific significance of enzymatic systems in its redox processes.

Observations showed that potassium humate contributes to a significant increase in the activity of both catalase and peroxidase in both reproductive and vegetative organs. Especially strong is the increase in the activity of respiratory enzymes under the influence of potassium humate in the initial phases of the development of the reproductive organs of stubble corn. Moreover, root fertilizations with potassium humate have a more prolonged effect on the activity of respiratory enzymes than foliar ones.

The Effect of Potassium Humate on Sugar Dynamics

Conducted studies on the sugar content in the reproductive and vegetative organs of stubble corn showed that at the initial stages of organogenesis, the sugar content in them was significantly lower than in the later period of development (Table 2).

Table 2. The Effect of Mineral Fertilizers and Potassium Humate on Sugar Dynamics in Stubble Corn

Plant Organs	Control		Root Fertilization N20, P20		Background + Potassium Humate 2 l/ha		Background + Potassium Humate 0.003%
	*reducing	**inverted	*reducing	**inverted	*reducing	**inverted	*reducing	**inverted
9-Leaf Phase
Tassel	1.74	3.52	1.23	2.05	1.51	4.35	-	-
Leaf	1.56	1.90	0.87	1.41	1.69	1.96	-	-
13-Leaf Phase
Tassel	1.13	2.37	0.64	2.30	0.92	2.37	0.95	2.30
Cob	1.41	3.01	1.41	2.50	1.41	3.78	1.41	3.33
Leaf	1.09	2.01	1.65	2.40	2.06	2.50	1.92	2.69
Tasseling Phase
Tassel	2.83	6.53	2.72	4.64	3.49	6.79	3.15	7.11
Cob	1.25	5.25	1.29	6.41	1.43	6.79	1.54	6.66
Leaf	1.93	3.48	1.98	5.25	2.32	5.25	1.98	5.25

Note: *reducing sugars, **inverted sugars.

The maximum amount of sugars in the tassel, cob, and leaves of stubble corn was observed in the tasseling phase. It should be noted the positive effect of potassium humate on sugar synthesis. On the variants where potassium humate was applied during fertilization, stubble corn plants contained more sugars than in the control.

Changes in Phosphorus Forms in Stubble Corn Plants Under the Influence of Potassium Humate

The conducted studies showed that the phosphorus content in the vegetative and reproductive organs of stubble corn is not the same and changes during its ontogenesis. The highest phosphorus content is found in the cob. At the beginning and end of tassel development, the phosphorus content is approximately at the same level. In the leaves, however, the phosphorus content fluctuates sharply during ontogenesis. The highest amount of this element in the leaves is found during the more intense periods of reproductive organ development, such as tassel differentiation and tasseling.

Potassium humate affects the distribution of phosphorus in plant organs, sharply increasing its content in the tassel of stubble corn immediately after fertilization. Under the influence of potassium humate, at the initial stages of development in the 9-leaf phase, a slight decrease in protein phosphorus was noted in the tassel, which led to a delay in tassel growth. Simultaneously, the content of acid-soluble phosphorus sharply increased in the tassel and leaves, indicating high energy activity in the biochemical processes occurring in the plant.

During the period of intensive growth of the tassel and cob, under the influence of potassium humate, the content of protein phosphorus in them significantly increased. In the leaves, during the initial period of organogenesis, under the influence of potassium humate, the content of organic phosphorus soluble in trichloroacetic acid increased, which is directly involved in energy processes.

Thus, under the influence of humic and fulvic acids, the amount of sugars in stubble corn plants increases, along with important forms of organic and inorganic phosphorus soluble in trichloroacetic acid in biochemical transformations, and the activity of respiratory enzymes increases, leading to an increase in the energy potential of the plant organism. This positively affected the formation of reproductive and vegetative organs of stubble corn and, ultimately, on plant productivity, i.e., on yield increase.