22 Apr 2014

Nutrient management for banana in China


Banana, one of the most important subtropical and tropical fruits, mainly grows in the provinces of Guangdong, Guangxi, Hainan, Fujian, Yunnan and Taiwan in China. Among the provinces, Guangdong has the largest cultivation area and produces the highest fruit yield and followed by Guangxi, Yunnan and Hainan (Table 1).
Table 1 Banana growing area and yield in southern China (Source: Agricultural Yearbook, 2012)
Province
Area
(ha)
Total yield
(t)
Unit area yield
(kg/ha)
Guangdong
125500
3848889
30.67
Guangxi
85100
2057463
24.18
Yunnan
79800
1687361
21.14
Hainan
65200
1892265
29.02
Fujian
27600
869735
31.51
Guizhou
1400
5900
4.21
Sichuan
1300
36499
28.08
Chongqing
100
1850
18.50
1. Soil and climate conditions
Soil and climate conditions significantly affect banana growth and nutrient management strategy. Soil fertility and capacity to retain nutrients and moisture can decide fertilizer rates and times of fertilizer applications, while climatic conditions determine sources, rates, times and placement of fertilizers.
Banana prefers soils with thick depths, slightly acid to neutral pH, rich in organic matter, medium texture and good drainage. In the fertile soils, banana requires lower fertilizer rates and fewer application times than in sandy or poor fertility soils.
Banana needs warm climate, bright sunshine and adequate moisture. Most varieties of banana grow best with 12 hours of bright light and humidity ≥ 50%. The ideal temperature range is around 26-30°C with relative humidity regime of 75-85%. Growth begins at 18ºC, reaches optimal growth at 27ºC and stop entirely when temperature reaches 38ºC. Although banana grows best in bright sunlight, high temperature will scorch leaves and fruit. Thus, under any adverse conditions that stress banana growth, fertilizing activities in the field should stop to avoid plant injury from fertilizers or lowered fertilizer use efficiency.
2. Nutrient requirement by banana
Banana belongs to herb family, grows for 10-14 months before fruit harvest and can produce more than 150 tons of dry biomass and up to 60 t of fresh fruits. For such large biomass, adequate supply of nutrients is vital to guarantee healthy growth and high yield. Like other crops, thirteen essential plant nutrients are required by banana including nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfer (S), boron (B), zinc (Zn), iron (Fe), manganese (Mn), copper (Cu), molybdenum (Mo) and chlorine (Cl). However, K is the key nutrient and required the most, followed by N and Ca. The quantity of these nutrients may vary from one variety to another, which can be generalized in the order of Pisang awak > Zhongba > dwarf > Baxi (Table 2). Take the variety Baxi – the most widely grown variety in China as an example, to produce 100 kg of fruit, it needs to absorb about 0.46 kg of N, 0.09 kg of P2O5, 1.81 kg of K2O, 0.25 kg of Ca and 0.12 kg of Mg.
Table 2 Nutrients required to produce one t of banana fruit (kg)
VarietyNutrients required
N
P2O5
K2O
Ca
Mg
ZhongbaQuantity
5.89
1.08
22.61
Ratio
1
0.18
3.84
DwarfQuantity
4.84
1.03
17.95
2.97
0.62
Ratio
1
0.21
3.71
0.61
0.13
BaxiQuantity
4.59
0.94
18.07
2.52
1.22
Ratio
1
0.20
3.94
0.55
0.27
Pisang awakQuantity
8.5
2.80
39.28
3.95
1.71
Ratio
1
0.33
4.62
0.46
0.20
3. Sources of fertilizers suitable for banana
In most of the banana fields, if not all, the indigenous nutrient supply from the soil cannot meet the demands of banana growth and thus, fertilizers must be applied timely based on the soil fertility, climatic conditions and plant growth. The fertilizer sources are suitable for banana include urea, ammonium sulfate, single superphosphate, mono-ammonium phosphate, di-ammonium phosphate, potassium chloride, potassium sulfate, potassium-magnesium sulfate, borax, zinc sulfate and so on (Table 3).
Table 3 Main nutrient sources commonly used for banana in China
Fertilizer sourceChemical formulaNutrient content
Macronutrient
UreaCO(NH2)246% N
Ammonium sulfateNH4SO421% N, 24% S
Single superphosphateCaH2PO412-18% P2O5, 18-21% Ca, 11-12% S
Mono-ammonium phosphateNH4H2PO410-12% N, 48-61% P2O5
Di-ammonium phosphate(NH4)2HPO418% N, 46% P2O5
Potassium chlorideKCl60% K2O, 45% Cl
Potassium sulfateK2SO450% K2O, 17-18% S
Potassium-magnesium sulfateK2SO4·2MgSO421-22% K2O, 10-11% Mg, 21-22% S
Elemental sulferS95-99% S
magnesium sulfateMgSO4·7H2O13-16% Mg, 13% S
Gypsum (dihydrate)CaSO4·H2O13% Ca, 18% S
Gypsum (Anhydrite)CaSO429% Ca, 23% S
Micronutrient
BoraxNaB4O7·10H2O11% B
Boric acid H3BO317% B
Zinc sulfateZnSO4·7H2O22% Zn, 11% S

Other fertilizers such as compound fertilizers in general, compound fertilizers specially designed for banana, slow-release and release controlled fertilizers, and organic manure are also suitable for banana. Different sources of fertilizers are usually used in combination to best meet nutrient requirement of banana.
4. Methods of fertilizer application
(1) Fertilizer rates
A suitable fertilizer rate used to a banana field is determined by soil fertility in combination with banana variety and yield goals. Amounts of soil available nutrients from soil testing are the basics in fertilizer recommendations. Once soil testing results are available, amounts of nitrogen and potassium for Baxi variety grown in the two major banana production bases can be determined according to Table 4 and Table 5. The nutrient rates for any other variety can be adjusted upon differences in nutrient requirement.
Table 4 Rating of soil nitrogen and potassium in relation to amounts of fertilizers recommended in the Pearl-River Delta Region
Soil alkali-hydrolysable N
(N, mg/kg)
N rate recommended
(N, kg/ha)
Soil available K
(K, mg/kg)
K rate recommended
(K2O, kg/ha)
>180
330~420
>300
375~525
150~179
420~480
200~299
525~600
120~149
480~540
150~199
600~675
90~119
540~600
100~149
675~750
60~89
600~660
50~99
750~825
<60
660~720
<50
825~900
Table 5 Rating of soil nitrogen and potassium in relation to amounts of fertilizers recommended in the west Guangdong
Soil alkali-hydrolysable N
(N, mg/kg)
N rate recommended
(N, kg/ha)
Soil available K
(K, mg/kg)
K rate recommended
(K2O, kg/ha)
>180
420~480
>300
600~675
150~179
480~540
200~299
675~750
120~149
540~600
150~199
750~825
90~119
600~660
100~149
825~900
60~89
660~720
50~99
900~975
<60
720~780
<50
975~1050
In the main banana production bases such as the Zhujiang Delta and Yangjiang county, Maoming city in the west Guangdong province, farmers are recommended to apply 525-600 kg of N, 135-220 kg of P2O5 and 630-990 kg of K2O to achieve high banana yield (≥ 45 t/ha). These are equivalent to 1125-1650 kg of urea, 1125-1800 kg of single superphosphate and 1050-1650 kg of potassium chloride. Besides, addition of 3 kg borax/ha is necessary.
It is highly recommended that frequent small applications of fertilizer, rather than fewer applications of greater amounts are preferred, unless the controlled release fertilizers are used. Usually, fertilizers are split into 6-8 times in one cycle of growing seasons. In addition, incorporate 600-750 kg lime/ha into soil at land preparation when the soil is acidic and top-dress 300-450 kg of MgSO4·H2O/ha during the growing season. In locations where farmers use organic manure, reduce 10%-15% of chemical fertilizer rates when every 7.5 t of organic manure is applied.
(2) Basal fertilizers
Transplanting of banana seedlings usually takes place during March to April. The fertilizer sources and rates for the basal application are determined before seedling transplanting. Combined use of organic manure and chemical fertilizers is recommended. If manure is unavailable, the proportions of the basal N and K fertilizers usually account for 1/3 of the total amounts, while 50% of total P, B and other fertilizers are used as basal application. All the basal fertilizers are incorporated into the soil around the seedling hills before seedling transplanting. When organic manure is used as a part of the basal fertilizers, the nutrients contained in the manure are subtracted from total amounts and basal application to avoid overdose of nutrients. Caution must be taken that any animal manure should be fully composted before use. Manures can be applied along ditches or incorporated into soil.
(3) Fertilizer applications during vegetative period (prophase)
The vegetative growth period of banana is also called prophase, which usually takes about 4 months after transplanting. In early spring when temperatures are below the optimal, banana roots grow at lower rates. The first topdressing of fertilizers can be performed at 15 days after transplanting, and the other two topdressings at very other one and half months. The rates of the three topdressings at the vegetative period can be used in an increment manner and controlled within 25% of the total N and 20% of K. The fertilizers can be banded or hill-applied into the top soil around the canopy. As plants grow bigger, the fertilizer bands or hills also move outward in correspondence to the change of canopy sizes. If compound fertilizers are used, their K2O/N ratio should be equivalent or close to 0.8 -1.0 to meet banana demands for these two nutrients. This can be calculated from the nutrient label on the fertilizer bag.
(4) Fertilizer applications during vegetative-reproductive period (mid-phase)
After 4 months vegetative growth, banana plants evolve into reproductive growth – bud initiation stage. Banana corm is emerged and expanded as garlic bulb-like shape. The period from bud initiation to budding stage is usually called mid-phase when vegetative growth and reproductive growth proceed side by side and roots grow vigorously. At this stage, banana is decreasing its demand for N but increasing for K. Thus, 40-42% of total N, 50% of total P, K, Mg and all B fertilizers are split into two topdressings. The first application at this phase is used at about one month after the last topdressing of the prophase and the second application in one and half months. Along the water-dropping lines of tree canopy, dig 2-3 arc-like bands (30 cm x 15 cm) at 5 cm deep and 40-50 cm away from the plant base, and broadcast fertilizers into the bands and cover with soil. Avoid the second fertilization at the same locations. If a double-row is planted on one hill, the fertilizer bands can be located at in-between rows. If it rains too much which usually results in shallow root growth or even roots expose in air, broadcasting rather than banding the fertilizers is more proper. When broadcast is used, times of fertilizer application should be increased and rates at each time should be reduced accordingly. When Fusarium wilt occurs, field work or soil disturbance should not be done at rain periods till soil surface is dried up to prevent from the disease spreading. Fertilizer broadcasting with reduced rates and increased application times is the best. When compound fertilizers are used during the mid-phase, choose fertilizers with K2O/N ratio equivalent or close to 1.2-1.4. Adjusting soil pH to neutral level makes the banana plant more resisting to Fusarium wilt disease.
Before budding, banana plants usually grow a number of suckers. Select one healthy sucker as daughter plant and remove the rest to reduce their competition for nutrients and moisture with the mother plant. Banana growing areas are susceptible to typhoon attacks in summer, and thus, the plants should be well propped with bamboo or other supporting materials when weather forecast identifies an incoming one.
(5) Fertilizer applications during reproductive period (late phase)
The period from budding to fruit harvest is called late phase. During this period, banana fingers swell fast and young shoots continue to generate. Usually, the fertilizers left (35% of total N, 30% of K and 50% of Mg) for this period will be applied in two times. The first time is right after cutting off the flower clusters and the second time is in one month later. If compound fertilizers are used, choose fertilizers with K2O/N ratio equivalent or close to 1.1-1.1.
5. Fertigation
Above - described is the traditional methods of banana fertilizer applications. Though it is less expensive, it is labor intensive and ineffective as nutrients may be leached out or evaporate after application. Drip irrigation has proved to be the most efficient manner in water management with uniform distribution of nutrients. In recent years, fertigation has become more and more popular in the banana production areas, especially for the large-scale growers.
6. Neutralizing soil acidity
Bananas prefer a slightly acidic to neutral soil, ranging from 5.5 to 7.0 on the pH scale. When soil pH becomes very acid (<5.5), banana is more susceptible to Panama disease. In acid soils, pH can be adjusted to pH 6.5-7.0 at 15-30 days before planting to give the amendment time to take effect. There are several amendments that can be used to raise your soil pH to better suit your bananas. The commonly lime materials used to raise soil pH are ground limestone or slaked lime (Ca(OH)2). About 230 g of ground limestone or 170 g of Ca(OH)2 per square meter raises pH by 1 point in loam soils. Clay requires slightly more and sandy soil less.
7. Diagnosis of nutrient deficiency, toxicity and correction
Imbalanced fertilization in banana production is not uncommon. When it occurs in severe degree, some symptoms will be seen in plants.
Banana is a typical K-lover, K deficient symptoms tend to appear on the leaves whenever K supply from the soil is inadequate. The symptoms of yellowing first appear on the older leave tips, and gradually spread to the basal part. Short nodes between leaves are obviously seen. K fertilizers should be added timely.

When N deficiency occurs, the symptoms of yellowing first evenly appear on the older leaves. Proper amounts of N fertilizers should be amended immediately.

When Ca deficiency occurs, growth of young leaves is stunted and irregular in shape. This is often induced by low soil Ca content and conditions of high temperatures and soil moisture. Spray 0.5% CaNO3 at a clear day can correct this problem. If the problem happens in the previous years, it indicates a deficiency in soil Ca and amount of 300-450kg/ha of CaNO3 should be considered in the fertilizer program.

Iron toxicity can be seen in banana as 1-cm black belt along the lower leaf rims. It usually occurs under high temperatures and humidity or after thunderstorms. To correct this problem, the most efficient method is to fast drain the ponding or excess water in the soil and timely broadcast ag-lime.

Improper placement of fertilizers such as fertilizer placed too close to plant stem can lead to stunted plant growth due to fertilizer damage.

Therefore, in order to achieve high yield and quality of banana and the best farmers’ profit, fertilizers must be applied with right sources, right rates, right time and right placement.

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