Black Plastic and a Growth Hormone Grew Bigger Cabbage, Faster
A nine-treatment field trial at RBS College, Agra, found that black polythene mulch paired with 50 ppm gibberellic acid produced cabbage heads that formed earlier, grew larger, and yielded about 30% more than untreated plants — with every other combination landing somewhere in between.
A factorial field trial on Pusa Mukta cabbage at RBS College, Bichpuri, Agra found that combining black polythene mulch with 50 ppm gibberellic acid (GA3) produced the heaviest, largest, and earliest-maturing heads of nine treatment combinations tested — 517.52 quintals per hectare against 398.00 q/ha for untreated control plants, a roughly 30% yield gain, with head initiation arriving nearly six days sooner.
The setup
Two cheap inputs, nine ways to combine them
Cabbage growers have plenty of individual tricks for pushing yield up — mulch to hold soil moisture down, growth regulators to push plant development along — but most trials test one or the other, not both together across a full range of doses. A team at the Department of Horticulture, RBS College, Bichpuri, Dr. BR Ambedkar University in Agra, set out to test mulching and gibberellic acid (GA3) as a combined system rather than two separate interventions, across every possible pairing.
The trial, run through the Rabi (winter) season of 2024-25 on the variety Pusa Mukta, used a factorial design with two independent factors: three mulching options (no mulch, black polythene, straw) crossed with three GA3 doses (0, 25, and 50 ppm), giving nine treatment combinations in total, each replicated three times in a randomized block layout.
The measurements
What actually got measured
The team tracked two families of outcomes at 90 days after transplanting. Growth parameters covered stem diameter, plant height, plant spread (both along and across the row), and the length and width of the largest leaf. Yield and quality parameters covered how many days it took heads to start forming, the fresh weight of the whole plant and of the trimmed head, head diameter, core length, yield per plot, yield per hectare, and specific gravity — a proxy for how dense and compact the head is.
The mulch effect
Black polythene beat straw beat nothing, on every single measure
Averaged across all GA3 levels, black polythene mulch (M1) outperformed straw mulch (M2), which outperformed no mulch at all (M0), on every growth and yield trait the trial measured — plant height (39.12 cm vs 36.20 cm vs 33.30 cm), head yield (463.84 vs 428.33 vs 414.00 q/ha), and everything in between. The paper attributes this to black polythene's edge in trapping soil moisture, suppressing weeds, and warming the root zone relative to straw or bare soil — conditions that let roots take up nutrients and water without interruption through the growing season.
GA3 showed a similar, independent pattern: averaged across all mulching types, 50 ppm (G2) beat 25 ppm (G1), which beat the untreated control (G0), on nearly every trait — plant height (39.85 vs 34.78 vs 34.00 cm), head yield (463.84 vs 426.33 vs 416.00 q/ha). As a plant growth regulator, GA3 promotes cell elongation and division, which shows up directly as taller plants, longer leaves, and ultimately larger heads.
The combination
The combination beat either input alone
The interaction is where the trial's real finding sits. M1G2 — black polythene mulch plus 50 ppm GA3 — didn't just add the two individual effects together, it topped every single measured trait outright: the tallest plants (45.58 cm vs a trial average of roughly 36 cm), the widest spread (52.33 cm along the row), the earliest head initiation (37.24 days, against 43.28 days for the untreated M0G0 control — nearly six days faster), the heaviest trimmed heads (0.72 kg vs 0.48 kg for M0G0), the largest head diameter (43.18 cm vs 33.78 cm for M0G0), and the highest yield per hectare (517.52 q/ha vs 398.00 q/ha for M0G0) — a roughly 30% yield gain from combining the two inputs over doing neither.
Every one of the eight other treatment combinations landed somewhere between those two extremes, tracking predictably with how much mulching and GA3 each one received. The straw-and-50ppm combination (M2G2) came closest to matching M1G2, but still trailed it on every trait — 445.00 q/ha in yield versus 517.52 q/ha, for instance.
The quality angle
Denser heads, not just bigger ones
One additional quality measure — specific gravity, a rough stand-in for how tightly packed a cabbage head is — also peaked at M1G2 (0.83, against 0.72 for the untreated control). That matters commercially: a denser head isn't just heavier for its size, it typically also stores and ships better, since more compact heads lose moisture and quality more slowly after harvest.
Both black polythene mulch and GA3 are inexpensive, widely available inputs for smallholder vegetable growers in North India, and neither requires specialized equipment to apply. A trial showing their combination reliably outperforms either input used alone — across yield, head size, earliness, and density — gives growers a concrete, low-cost package to test on their own cabbage plots rather than having to choose between competing single-input recommendations.
Why did black polythene mulch outperform straw mulch?
The paper attributes it to black polythene's stronger effect on soil moisture retention, weed suppression, and root-zone warming compared to straw or bare soil, creating more favorable conditions for continuous nutrient and water uptake through the growing season.
Is more GA3 always better?
Within the doses tested here, yes — 50 ppm outperformed 25 ppm and the untreated control on nearly every measured trait, both alone and combined with mulch. The trial did not test doses above 50 ppm, so it cannot speak to whether returns diminish or reverse beyond that level.
What variety of cabbage was used?
Pusa Mukta, grown during the Rabi (winter) season of 2024-25 at the Agriculture Research Farm, Department of Horticulture, RBS College, Bichpuri, Agra.
How was the trial structured?
A Factorial Randomized Block Design (FRBD) with three mulching treatments (none, black polythene, straw) crossed with three GA3 doses (0, 25, 50 ppm), giving nine treatment combinations, each replicated three times.
Based on the peer-reviewed paper “Response of Mulching and GA3 on the Performance of Cabbage (Brassica oleracea var. Capitata)”. Read the full abstract, key findings, and download the PDF on the paper's own page.