The Effect of Potassium Humate on the Morphogenesis of Stubble Corn
It is known that phenological observations record the appearance of formed fruiting organs, but a large and important period of their formation remains hidden from the observer's eye. To observe the formation of fruiting organs, the so-called morphophysiological analysis should be used, which involves sequential observation of the formation process of each organ in plants in connection with living conditions, especially the fruiting organs of male and female inflorescences of corn.
To observe the formation of the tassel and cob, we dissected the main and axillary buds of 10 stubble corn plants, then examined them under a binocular loupe, determined their organogenesis stage, measured, and photographed them.
The results of the measurements of the tassel apex of corn are presented in Table 3.
Table 3. The Effect of Mineral Fertilizers and Potassium Humate on the Size of the Tassel of Stubble Corn
| Development Phases | Control | Root Fertilization N20P20 | Background + Root Fertilization with Potassium Humate | Background + Foliar Fertilization with Potassium Humate | ||||
|---|---|---|---|---|---|---|---|---|
| Tassel Size, mm | Control, % | Tassel Size, mm | Control, % | Tassel Size, mm | Control, % | Tassel Size, mm | Control, % | |
| 7 Leaves | 0.5 | 100 | 0.5 | 100 | 0.5 | 100 | - | - |
| 9 Leaves | 1.6 | 100 | 1.7 | 106 | 1.2 | 68 | 8.9 | 95 |
| 11 Leaves | 7.2 | 100 | 10.1 | 108 | 23.0 | 131 | 22.5 | 128 |
| 13 Leaves | 16.5 | 100 | 17.5 | 106 | 30.0 | 182 | 31.3 | 190 |
| Tasseling | 22.5 | 100 | 25.2 | 112 | 31.4 | 140 | 33.5 | 149 |
The data show that after root fertilization with potassium humate in the 9-leaf phase, a slight decrease in the size of the primordial tassel was observed.
Humic and fulvic acids especially stimulate the development of the root system. During this period, stubble corn formed secondary roots, and evidently, the main tension of biochemical processes was transferred to them. This may be related to the decrease in protein phosphorus in the tassel in the 9-leaf phase and its smaller size compared to the control.
However, subsequently, the growth of the tassel under potassium humate significantly outpaced the growth of the tassel in the control and mineral background groups.
Under the influence of mineral fertilizers and potassium humate, stubble corn also showed an increase in cob size.
For example, the cob size in the 14-leaf phase exceeded the control by 8.3% in the mineral background group, by 33.3% with additional root fertilization with potassium humate, and by 27.7% with foliar fertilization.
Under the influence of potassium humate, along with increased growth intensity, accelerated plant development was observed: earlier differentiation of the tassel apex, earlier formation of flowers in spikelets, pollen in anthers, and accelerated tassel growth, which contributed to faster tasseling. This is evidenced by the data in Table 4.
Table 4. The Effect of Potassium Humate on the Development of Reproductive Organs in Stubble Corn
| Experiment Variants | Percentage of Plants with Tassels Emerged | Percentage of Plants with Simultaneously Flowering Tassels and Cobs on 16.09 |
|---|---|---|
| Control | 12.1 | 14.0 |
| Root Fertilization, N20P20 (Background) | 10.1 | 15.8 |
| Background + Potassium Humate, 30 kg/ha (Root Fertilization) | 18.8 | 24.0 |
| Background + 0.003% Potassium Humate (Foliar Fertilization) | 18.0 | 19.3 |
It should also be noted that under the influence of potassium humate, the gap between the flowering of male and female reproductive organs in stubble corn is reduced. This leads to better pollination and better kernel set in the cobs, enhancing the feed quality of stubble corn.
Fertilizing crops with potassium humate accelerated corn development and contributed to an increase in the yield of formed cobs (Table 5).
Table 5. The Effect of Mineral Fertilizers and Potassium Humate on the Yield of Stubble Corn Cobs Under Irrigation (2019 Data)
| Experiment Variants | Average Cob Yield, c/ha | Yield Increase Over Control, c/ha | Yield Increase Over Control, % | Yield Increase Over Background, % |
|---|---|---|---|---|
| Control | 100.4 | - | - | - |
| Root Fertilization, N20P20 (Background) | 89.4 | -11.0 | -21.8 | 52.4 |
| Background + Potassium Humate, 30 kg/ha (Root Fertilization) | 112.8 | +12.4 | +24.6 | - |
| Background + 0.003% Potassium Humate (Foliar Fertilization) | 104.8 | +4.4 | +8.6 | 34.4 |
It should be noted that formed cobs in stubble corn appear only in years favorable for its development (sufficient warmth, optimal moisture, abundant solar radiation). Such years during our research were 2018 and 2019.
Table 6. The Effect of Mineral Fertilizers and Potassium Humate on the Green Mass Yield of Stubble Corn Under Irrigation
| Experiment Variants | Green Mass Yield, c/ha | Average Yield Over 4 Years (2016-2019), c/ha | Increase Over Control, % | |||
|---|---|---|---|---|---|---|
| 2016 | 2017 | 2018 | 2019 | |||
| Control | 196.4 | 425.2 | 232.4 | 225.3 | 269.8 | - |
| Root Fertilization, N20P20 (Background) | 204.3 | 469.5 | 273.3 | 247.5 | 298.7 | 10.7 |
| Background + Potassium Humate (Root Fertilization) | 217.1 | 513.8 | 290.3 | 272.9 | 323.5 | +19.9 |
| Background + 0.003% Potassium Humate (Foliar Fertilization) | - | - | - | 262.8 | - | +16.6 |
Note. X - not determined.
Stubble corn crop (photo from September 8, 1961)
The data in Table 5 show that fertilization with ammonium nitrate and superphosphate reduced the cob yield even compared to the control. This can likely be explained by the fact that nitrogen stimulated the growth of the vegetative mass of corn, which led to some increase in green mass yield in this variant (see Table 6 above), but cob formation was delayed. Fertilization with potassium humate, applied against the mineral background, had a positive effect not only on the green mass yield of stubble corn but also accelerated cob development. As a result, the yield of formed cobs in the variant with potassium humate exceeded the control by 4.3-12.3% and the mineral background by 17.2-26.2%.
Four-year experiments in our farm indicate that under irrigation in the Dnipropetrovsk region, high yields of green mass of stubble corn can be obtained (see Table 6). The highest increase in green mass of stubble corn—53.7 c/ha—was obtained from root fertilization with potassium humate against the background of ammonium nitrate and superphosphate. On average over four years (2016-2019), this increase was 19.9%.
Conclusions
- Under the influence of potassium humate, significant shifts in biochemical processes are observed in stubble corn plants, including increased activity of respiratory enzymes, accumulation of sugars, and higher phosphorus content in reproductive organs, especially in inorganic and organic acid-soluble forms.
- Fertilizing stubble corn crops with potassium humate significantly accelerates the growth and development of plants, specifically the formation and growth of tassels and cobs at all stages of their organogenesis. As a result, the number of formed cobs increases significantly in crops fertilized with potassium humate.
- The intensification of physiological processes in plants under the influence of potassium humate and mineral fertilization positively impacted the yield of green mass and cobs of stubble corn. The yield increase of green mass together with cobs in this variant over four years (2016-2019) compared to the control was 19.9%, and compared to the background (N20P20) was 9.2%.
- To accelerate the growth and development of stubble corn, fertilization with potassium humate combined with N20P20 should be implemented in production, as it is a highly effective agrotechnical practice.