Potassium Lifts Ginger Production in Bangladesh

Growers of ginger in Bangladesh are getting detailed evidence of how to get significant yield boosts of up to 67% by providing their crop with the optimum dose of potassium alongside other key nutrients.

 

Appetite for Ginger

Ginger is one of the major spice roots grown in Bangladesh and is highly valued in daily life for its flavor and for its medicinal properties. Shoppers in this East Asian country like to buy their ginger in many ways: raw, dried, bleached, powdered, as ginger oil, ginger candy, ginger flakes, and more.

Ginger needs good levels of nutrients to thrive. It is accepted that, per hectare, a crop of ginger can remove as much as 400 kg nitrogen, 32 kg phosphorus and 394 kg potassium from the soil. The high potassium requirement makes ginger especially sensitive to low levels of this essential nutrient, an increasingly common occurrence, and one of the reasons why gains in agricultural productivity have stalled.

 

Inadequate Potassium is Holding Crops Back

It is a welcome trend that agricultural productivity overall in Bangladesh has increased markedly in the last couple of decades. However, examine the detail and it is evident that, for many crops, yields have plateaued or, in some instances, declined.

Several contributing factors may have caused this including depletion of soil organic matter and imbalanced use of fertilizers. Continuous and high rates of nitrogen use by farmers has become the norm, but little attention has been given to the role of other essential nutrients. In fact, potassium has now replaced nitrogen as the nutrient that is severely limiting yield of many crops, including ginger.

 

Role of Potassium in Ginger

Soil potassium levels are reported as low in the many parts of Bangladesh that produce ginger. In the most intensively farmed regions potassium deficiencies are causing serious effects. Whilst soil potassium levels might have sustained local crop varieties with low yield potential for season after season, as farmers have switched to higher yielding, or even super hybrid varieties, the widespread potassium deficiency in Bangladesh soils has become apparent. Ginger growers have not been enjoying the yields or profitability that they should.

The good news is that with adequate potassium, yields are enhanced, disease resistance is improved, as are the plant-water relationship and photosynthesis. It also raises the quality, marketability, and profits in the crop.

 

Investigating the Benefits of Redressing the Lack of Potassium

To determine the effects of using potassium fertilizer, a team from the Bangladesh Agriculture Research Institute Spices Research Centre designed and ran a comprehensive experiment. Over two growing seasons, and using a commonly grown ginger variety, the trial aimed to establish the optimum application rate of potassium (whilst all other nutrients were adequately supplied) to maximize yield and nutrient uptake, and provide best economic return for the farmer.

In total, five different potassium application rates were compared with a control with no potassium applied. The highest potassium dose was 160 kg/ha.

 

Measurements Taken

At the site, and before any application of nutrients, initial soil samples (from the 0-15 cm soil depth) revealed that it was slightly acidic, intensively leached, and there was inadequate potassium, amongst other nutrients. As the experiment progressed, soil samples were repeated and plant samples from each of the trial plots were taken and dried to analyze for potassium uptake.

 

Table showing yield contributing characters of ginger as influenced by different K application rates.

Treatment	Plant height (cm)		No. of tillers/plant		No. of leaves/plant
	2010-2011	2011-2012	2010-2011	2011-2012	2010-2011	2011-2012
T1 (K0)	65.00	56.9 b	13.4 c	10.0 d	161.9 b	90.2 d
T2 (K40)	68.83	59.3 b	14.7 ab	11.4 cd	177.8 ab	114.9 c
T3 (K80)	76.20	62.8 b	15.5 a	12.6 bc	205.8 a	132.2 b
T4 (K120)	73.53	68.9 a	15.5 a	16.5 a	211.5 a	164.5 a
T5 (K160)	71.53	66.7 a	14.3 bc	13.9 b	201.3 ab	145.4 b
CV (%)	NS	4.0	3.8	7.6	11.2	6.2
Note: Figures in a column having same letter(s) do not differ significantly at 5% level by DMRT.

 

Advice for Potassium Levels in Balanced Fertilizer Strategy

The improved potassium levels had physically observable effects on the growing ginger crop. Leaf and tiller numbers increased. Fresh rhizome weight per plant increased dramatically.

The best yield (numbers of tillers and leaves) and quality attributes in ginger were recorded (see table above) with potassium applied at up to 120 kg/ha. Likewise, the highest rhizome yield by far was from potassium dose of 120 kg/ha with a yield increase of up to 67% (see table below).

 

Table showing ginger yield as influenced by different K application rates.

Treatment	Rhizome weight/plant		Fresh rhizome yield		Yield increase over control
	2010-2011	2011-2012	2010-2011	2011-2012	2010-2011	2011-2012
	g	g	mt/ha	mt/ha	%	%
T1 (K0)	245.0 d	183.3 c	12.8 c	9.6 d	-	-
T2 (K40)	290.0 c	203.0 bc	15.2 b	11.3 cd	19	18
T3 (K80)	350.0 ab	217.0 bc	16.1 ab	12.4 bc	26	29
T4 (K120)	380.0 a	273.3 a	17.6 a	16.0 a	38	67
T5 (K160)	330.0 b	232.0 b	14.5 bc	13.7 b	13	43
CV (%)	5.3	8.1	7.4	9.1	-	-
Note: Figures in a column having same letter(s) do not differ significantly at 5% level by DMRT.

 

According to the response curve plotted using the measurements of ginger rhizome yield from all the treatments (below), the optimum potassium dose in this trial was actually 122 kg/ha.

Interestingly, the best return on investment for the farmer (considering the cost of purchasing and applying the potassium alongside other nutrients needed by the crop) was at the dose of 120 kg/ha.

 

 

Corroborating Evidence from other Research on Potassium for Ginger

The findings from the research carried out in Bangladesh are in a similar range to the results from potassium dose testing in ginger in China. There too, potassium is respected as key to ginger quality as it indirectly improves nitrogen use efficiency and protein formation in the plant and benefits the size, weight, oil content, and color of the marketable ginger. Other ginger research, in India, has also found that application of adequate potassium to ginger increased the yield and size of the rhizome fingers. Potassium also increased the concentration of oleoresin, which is the source of the characteristic flavor and fragrance from ginger that consumers value so highly.

With the strong domestic demand for ginger in Bangladesh there will be ongoing interest in ways to finetune the agronomic care invested in the crop. In the meantime, farmers have been given the chance to understand, prioritize, and optimize the potassium dose to get the best yield and reliable economic returns from every crop of ginger they grow.

For more information about this research see the full report published in the e-ifc by the International Potash Institute (IPI).