Table 1. Situation of inorganic fertilizer use in Vietnam
Unit: Ton
Nutrition
2013 | 2014 | 2015 | 2016 | 2017 | |
N | 1,628,286 | 1,363,887 | 1,695,781 | 1,548,983 | 1,548,799 |
P2O5 | 853,070 | 872,509 | 755,722 | 824.152 | 873.003 |
K2O | 626,365 | 563,584 | 575,621 | 598,959 | 764,285 |
Total nutrients | 3,107,721 | 2,799,980 | 3,027,124 | 2,972,094 | 3,186,087 |
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Experiment 1: Study on the Effect of Potassium and Sulfur Fertilizer Dosage on Coffee and Tea Plants in the Business Stage on Red-Brown Basalt Soil in Lam Dong Province -
Effect of Potassium and Sulfur Dosage on Theoretical Yield and Actual Yield of Arabica Coffee Plants in the Commercial Stage -
Research on building coffee tourism products into one of the main brands of Dak Lak tourism - 2 -
Research on some technical measures for fertilizing Coffea canephora Pierre coffee trees in the business stage on basalt soil in Dak Lak - 25 -
Research Approach and Bank Credit Analysis Framework for Coffee Producers
(Source: O, 2020) [97].
FAO (2017) statistics in Table 1.10 show that: Potassium fertilizer consumption in crop production in Vietnam from 2011 to 2015 was relatively stable, reaching its highest level in 2011 (594.1 thousand tons); equal to 29.8% NPK; 61.5% N, 137.2% P. In 2012, 2013 and 2014, potassium fertilizer consumption decreased slightly. In 2015, potassium fertilizer consumption was equal to 22.6% NPK; 44.3% N and 85.7% P. On average for the entire period from 2011 to 2015, K consumption was equal to 24.0% NPK; 45.6% N and 106.2% P.
Table 1.10. Potassium consumption compared to nitrogen and phosphorus in Vietnam (2011-2015)
Year
K consumption (1,000 tons) | NPK consumption (1,000 tons) | K/NPK (%) | Y/N (%) | K/P (%) | |
2011 | 594.1 | 1,992.7 | 29.8 | 61.5 | 137.2 |
2012 | 501.7 | 2,124.8 | 23.6 | 43.1 | 109.3 |
2013 | 623.2 | 2,828.5 | 22.0 | 38.8 | 104.1 |
2014 | 561.5 | 2,546.8 | 22.0 | 40.3 | 94.8 |
2015 | 600.0 | 2,654.0 | 22.6 | 44.3 | 85.7 |
Average K/NPK, K/N, K/P ratio | 24.0 | 45.6 | 106.2 | ||
(Source: O, 2017) [97].
Note: Unit of measurement K=K 2 O, P=P 2 O 5 .
Author Nguyen Van Bo (2017) surveyed the use of inorganic fertilizers for coffee trees in the Central Highlands from 2011 to 2012. The results showed that: The amount of potassium that farmers in Dak Lak and Gia Lai provinces fertilized for Robusta coffee fluctuated from 48 to 1,900
kg K 2 O/ha/year; average is 425 kg K 2 O/ha/year. In Lam Dong province alone, farmers fertilizing coffee with potassium fluctuates in a lower range, from 32 to 1,707 kg K 2 O/ha; average is 414 kg K 2 O/ha [3].
The survey results of Lam Van Ha (2014) on the current status of nitrogen, phosphorus, potassium and sulfur fertilizer use on Robusta coffee trees in Lam Dong province showed that: The use of nitrogen, phosphorus, potassium and sulfur fertilizers for Robusta coffee trees in the commercial stage in Lam Dong is not reasonable in terms of dosage, ratio and fertilization techniques. Most farmers apply nitrogen, phosphorus and sulfur at higher levels than recommended (448.4 kg N/ha; 324.0 kg P 2 O 5 /ha and 323.6 kg S/ha/year). However, the amount of potassium applied to Robusta coffee trees is lower than recommended, ranging from 80 to 250 kg K 2 O/ha/year. The ratio of nitrogen, phosphorus and potassium elements is also not balanced according to the needs of Robusta coffee trees (N:P 2 O 5 :K 2 O:1.38:1:0.94). Most farmers use NPK fertilizer: 16:16:8+13S to fertilize Robusta coffee trees, less commonly used single fertilizers such as urea, superphosphate, potassium chloride [17].
Author Dinh Thi Tieu Oanh (2018) surveyed the current status of fertilizer use for tea coffee plants on red-brown basalt soil in Lam Dong, the results showed that: Over 90% of surveyed households use NPK fertilizer to fertilize tea coffee plants; the commonly used NPK ratio is 16:16:8+13S or 7:7:14 or 20:20:15 or 16:8:16+6S. Single fertilizers such as urea, potassium chloride, potassium sulphate are also less commonly used for tea coffee plants. The N:P:K fertilizer ratio commonly used for tea coffee plants in the commercial stage in Lam Dong is commonly 2.5:1.2:2.75. The amount of potassium commonly used is 222.2 kg K 2 O/ha/year, lower than the recommended level [38].
In summary, the survey results on the current status of inorganic fertilizer use for coffee trees in the Central Highlands by many authors have shown that: N, P, K and S fertilizer application for coffee trees is not balanced and reasonable; most farmers apply higher amounts of nitrogen, phosphorus and sulfur than recommended while applying lower amounts of potassium. Thus, the use of potassium and sulfur fertilizers is not suitable for the needs of coffee trees in the Central Highlands.
1.3. RELATED RESEARCH WORKS
1.3.1. Research results on potassium for coffee plants
1.3.1.1. In the world
According to Forestier (1969): On Arabica coffee trees, potassium deficiency symptoms usually appear on the 3rd to 4th pair of mature leaves from the top of the branch to the main stem, not on the young pairs of leaves at the top of the branch. The recommended amount of potassium fertilized is from 150 to 300 kg K 2 O/ha/year to stabilize coffee yield from 3 to 4 tons of beans/ha/year. Potassium content
suitable in coffee leaves from 2 to 2.2% (early rainy season is 1.9% and mid rainy season is 2.1%) [72].
Studies by De Geus (1973) showed that: Mature coffee trees annually remove from the soil 145 kg K 2 O / ha. Different doses of potassium do not lead to significant changes in the content of caffeine and chlorogenic acid (a compound partly responsible for the sour taste of a cup of coffee) [71].
According to Iyenngar and Awatranami (1975): For every 1 hectare of Arabica coffee with an average yield of 5 kg/tree/year, 450 kg of K2O / year is needed [74].
The research results of Krishnamurthy Rao (1991) showed that: With density
1,075 trees/ha, the recommended amount of potassium fertilizer for Robusta coffee to produce 1 ton of beans requires 80 kg of K2O / ha/year, divided into 2 applications, March (before flowering) and October (after the rainy season). When the bean yield is over 1 ton/ha/year, 120 kg of K2O / ha/year is needed, divided into 3 applications, March (before flowering), May (after flowering) and October (end of the rainy season) [77].
Studies on the effects of magnesium and potassium on coffee bean quality by Willson (1987) showed that: When the ideal nutritional balance is lost, the quality of coffee beans tends to decrease. Applying magnesium to coffee in the case of potassium deficiency reduces the quality of coffee beans. When applying enough potassium, the quality of drinking water is improved. Excess potassium application causes antagonism with magnesium. Coffee plants do not absorb enough magnesium, beans have a pale yellow color, and the quality of drinking water decreases [96].
Surveys by Jayarama and Ramaiah (1988) showed that: The recommended amount of potassium for coffee plants in 17 countries around the world varied from 25 to 200 kg K 2 O/ha/year [75].
The results of the study by Brarel and Jacquet (1994) on the effect of potassium dosage on the drinking water quality of Arabica coffee plants in Brazil showed that: Excess potassium in coffee beans makes the coffee drink harsher and more astringent . Excess potassium fertilizer can improve the yield of coffee beans but reduce the quality of drinking water [67].
De Barros Silva (2002) studied the relationship between potassium fertilizer dosage and coffee cup quality, the results showed that: No potassium fertilizer or potassium fertilizer at the rate of 400 kg K 2 O/ha/year reduced the quality of coffee cup. The activity of polyphenol oxidase enzyme (U/g) in the formula of no potassium fertilizer and potassium fertilizer at the rate of 400 kg K 2 O/ha/year only reached from 58 to 61.4 U/g; the formula of potassium fertilizer at the rate of 200 kg K 2 O/ha/year reached the highest (65.5 U/g), the color index and total sugar content in coffee beans were also higher than other fertilizer levels when measured at a wavelength of 435 nm.
High polyphenol oxidase enzyme results in better quality coffee cups, more aromatic drinks and smoother taste [99].
Studies by Snoeck and Lambot (2004) on the dosage and form of potassium fertilizer on Arabica coffee trees in Brazil showed that: Inappropriate potassium levels increase the rate of empty beans, reducing the quality of drinking water. Excessive application of manure or the use of elephant grass as a mulch (high in potassium) causes many brown beans, which are considered poor quality beans for green coffee. Drinking water quality is improved when potassium is applied in the form of K 2 SO 4 fertilizer . The best balance between quality and yield is achieved when using K 2 SO 4 fertilizer at a dosage of 200 kg K 2 O/ha/year. Applying K 2 SO 4 at a dosage of over 330 kg K 2 O/ha/year does not significantly affect
coffee yield but counteracts the effect of potassium fertilizers. Potassium fertilizers in the form of K2SO4 provide better results than KCl, because the accumulation of Cl - in the plant has a negative impact on the quality of the coffee drinking water. The quality of coffee beans when fertilized with potassium under
K 2 SO 4 and KNO 3 forms are better than KCl [86].
Kant (2005) also compared the effects of two sources of potassium fertilizers, K 2 SO 4 and KCl, on the yield and quality of Arabica coffee in Brazil with the applied dosages for each form of potassium fertilizer being 100; 200; 400 kg K 2 O/ha/year, respectively. The results showed that there was a statistically significant difference in the yield of green coffee beans in the years 1999, 2000 and 2001. The yield of green coffee beans when fertilized with potassium in the form of K 2 SO 4 was higher than that when fertilized with KCl by 11.4%; 19.8% and 4.2%, respectively [76].
Mancuso (2014) studied the effects of 4 potassium doses (0; 75; 150; 300 kg K 2 O/ha/year) and 2 forms of potassium fertilizer (KCl and phonolite powder) on Arabica coffee yield in Brazil from 2008 to 2010. The results showed that: Potassium fertilization at doses of 75, 150 or 300 kg K 2 O/ha/year in the form of KCl or phonolite powder increased yield compared to the control (no potassium fertilization). At the dose of 150 kg K 2 O/ha/year, Arabica coffee yield in both forms of potassium fertilizer was not significantly different. Thus, phonolite powder can be used to provide potassium for Arabica coffee plants, replacing imported KCl [81].
1.3.1.2. In Vietnam
Research on nutrition for coffee trees in the Central Highlands by author Phan Quoc Sung (1987) recommended the amount of potassium fertilizer and the time of potassium fertilization for Arabica coffee trees in the business stage to be 200 kg K 2 O / ha / year and 3 fertilizations with the following ratio: 1st time (May), 30% fertilization; 2nd time (June to July), 35% fertilization and 3rd time (September to October),
35% fertilizer [40].
The research results of Ton Nu Tuan Nam (2003) on the effects of potassium fertilizer dosage on Robusta coffee trees in the Central Highlands showed that: The rate of fruit branch drying disease caused by the fungus Colletotrichum gloeosporioides was significantly reduced when fertilized.
Potassium and nitrogen are adequate, but coffee growing soil is not fertilized with potassium, after a few harvests it will be seriously depleted of potassium and potassium deficiency symptoms will appear clearly on the leaves [32].
Luong Duc Loan and Le Hong Lich (1997) stated that: The potassium fertilizer utilization coefficient is related to the potassium fertilizer rate and the organic content in the soil. Fertilizing 200 to 400 kg K 2 O/ha/year on an organic fertilizer base of 10,000 kg/ha/year, fertilizing once every 2 years, the potassium fertilizer utilization coefficient increases from 47.3 to 52.8%. On a base without organic fertilizer, the potassium fertilizer utilization coefficient is lower, from 44.2 to 45.8% [25].
Research results of Le Ngoc Bau (1997) on the effect of green pressing of plant residues on coffee yield and potassium content in red-brown basalt soil in Dak Lak, the research results showed: The content of easily digestible K2O in the soil in the control formula was 7.42 mg/100 g of soil, lower than the formula of digging trenches to press plant residues at 8.13 mg/100 g of soil and the formula of tilling and stirring was 9.83 mg/100 g of soil [1].
Authors Ton Nu Tuan Nam and Truong Hong (1999) studied the effect of potassium fertilizer dosage on the quality of Robusta coffee beans on red-brown basalt soil in the Central Highlands. The results showed that: Fertilizing with 125 kg K 2 O/ha/year, the average weight of 100 beans was 13.2 g and the average grade 1 bean ratio was 67.4%; fertilizing with 250 kg K 2 O/ha/year, the average weight of 100 beans was higher (13.36 g) and the grade 1 bean ratio was also higher at 70.9%, but when fertilizing at 375 kg K 2 O/ha/year, the weight of 100 beans and the grade 1 bean ratio were not improved compared to 125 kg K 2 O/ha/year [30].
According to author Nguyen Xuan Truong (2000), after studying the timing and rate of potassium fertilization for Robusta coffee trees on red-brown basalt soil in the Central Highlands, he proposed the following formula for potassium fertilization for Robusta coffee: At the beginning of the rainy season, apply 20 to 25% of the total amount of potassium; in the middle of the rainy season, apply 30 to 35% of the total amount of potassium; at the end of the rainy season, apply 30 to 35% of potassium; at the beginning of the dry season, apply 5 to 10% of the total amount of potassium. The amount of potassium fertilizer for Robusta coffee trees during the business stage and after re-felling on red-brown basalt soil is from 260 to 400 kg K 2 O/ha/year; on non-basalt soil is from 300 to 450 kg K 2 O/ha/year [62].
Research results of author Duong Hong Dat (2000) show that: In the business stage, balanced fertilization of potassium and nitrogen is very effective. On red-brown basalt soil, potassium fertilization increases Robusta coffee yield from 0.77 to 1.77 tons/ha/year, the efficiency of using 1 kg of K 2 O is 35.9 kg of dry coffee beans [14].
Research results of Nguyen Thi Quy Mui (2001) also showed: The amount of potassium fertilizer for Robusta coffee in the business stage on red-brown basalt soil is 200 kg K 2 O/ha/year and after sawing and restoration is 150 to 200 kg K 2 O/ha/year. Potassium is divided into 3 fertilization times: 1st time (early rainy season, March to April), 35% fertilization; 2nd time (mid-rainy season, June to July), 40% fertilization; 3rd time (late rainy season, October to November), 25% fertilization [28].
Technical process for planting, caring for and harvesting Robusta coffee 10 TCN 527-2002 of the Ministry of Agriculture and Rural Development (2002) recommends the amount of potassium fertilizer for Arabica coffee in the business stage on red-brown basalt soil to achieve a yield of 2 to 2.5 tons/ha/year is from 270 to 300 kg K 2 O/ha/year. Potassium fertilizer is divided into 4 fertilization times: 1st time (March, 20%), 2nd time (May, 30%), 3rd time (July, 30%) and 4th time
(September, 20% fertilizer) [46].
According to author Ton Nu Tuan Nam (2003): To achieve a yield of 4.5 to 5 tons of beans/ha/year, it is necessary to apply 14 to 15 tons of decomposed organic fertilizer, 300 to 350 kg of N, 80 to 100 kg of P 2 O 5 , 300 to 350 kg of K 2 O to Robusta coffee in the commercial stage. Higher fertilizer doses also increase yield but are not economically effective when the selling price of coffee beans is 10,000 VND/kg [32].
Research results of Le Hong Lich (2005) have shown that: The amount of potassium fertilizer for Robusta coffee in the business stage to achieve a yield of 3.5 to 4 tons/ha/year requires 500 kg of KCl; for every 1 ton of coffee beans increasing or decreasing, the amount of fertilizer above can be increased or decreased by 10 to 15%. Multi-element fertilizer can be used with the amount of fertilizer from 1.5 to 2.0 tons of NPK/ha/year. The amount of KCl is divided into 3 fertilization times: 1st time (April to May), 160 kg of KCl; 2nd time (June to July), 170 kg of KCl; 3rd time (August).
to 9), apply 170 kg KCl [23].
The research results of Y Kanin H'Dơk and Trinh Cong Tu (2007) showed that: The amount of potassium fertilized for Robusta coffee gardens in the business stage on red-brown basalt soil in Dak Lak to achieve the highest productivity and economic efficiency is 400 kg K 2 O/ha/year, productivity increased by 62.5%, net profit was 16.32 million VND/ha/year [16].
According to author Nguyen Tien Si (2009): Fertilizing 350 kg K 2 O/ha/year for Robusta coffee in the commercial stage grown on red-brown basalt soil in Dak Nong province gave the highest yield of 3.76 tons of beans/ha/year; net profit reached 70 million VND/ha/year [43].
The recommendation of Lam Dong Provincial Agricultural Extension Center (2009) on the use of potassium fertilizer for coffee and tea plants in the commercial stage on red-brown basalt soil to achieve a yield of 2.5 to 3.0 tons is from 451 to 501 kg KCl/ha/year. KCl is divided into 3 fertilizations: 1st time (April to May), 30% fertilization; 2nd time (June to July), 30% fertilization; 3rd time
(September to October), apply 40% [103].
The Department of Crop Production, Ministry of Agriculture and Rural Development (2010) recommends the amount of potassium fertilizer at the yield levels achieved for replanted coffee gardens as follows: A yield of 3 tons/ha/year requires 230 kg K 2 O /ha/year; a yield of 4 tons/ha/year requires 300 kg K 2 O/ha/year; a yield of 5 tons/ha/year requires 370 kg K 2 O/ha/year [12].
The results of the study on intensive farming methods in commercial tea coffee production in the Northern mountainous region by author Vu Hong Trang (2011) showed that: The recommended dosage of potassium fertilizer for 1 hectare of tea coffee in the commercial stage in the Northern mountainous region is 300 kg K 2 O/ha/year. Potassium is divided into 2 fertilizations: The first time at the beginning of the rainy season (April), fertilizing 50% and the second time in the middle of the rainy season (August), fertilizing 50% [61].
Author Bui Van Hung (2011) recommends the amount of potassium fertilized for 1 hectare of tea coffee on hilly land in Phu Quy, Nghe An province is 120 kg K 2 O, the highest tea coffee yield is 15 tons of fresh ripe fruit/ha/year, the profit is 26 million/ha/year and higher than the control from 10 to 12 million VND/ha/year [21].
The results of the study on technical measures for fertilizing Robusta coffee in the business stage on red-brown basalt soil in Dak Lak province by author Nguyen Van Minh (2014) showed that: Applying potassium fertilizer at a dose of 336 kg K 2 O / ha / year increased the weight of fresh ripe fruit by 10%; reduced the fresh/kernel ratio by 7% compared to the control (according to the recommended process); gave the highest profit (83.11 million VND / ha / year). Applying potassium fertilizer twice a year (30% in the dry season and 70% in the rainy season) increased the ability of coffee trees to absorb N, P; increased chlorophyll a content by 17%; increased photosynthetic intensity by 23%; increased reserve branch length by 8%; reduced fruit drop rate (3.93%) compared to the control formula [27].
Tran Minh Tien's (2015) study on the effects of 6 doses of potassium chloride fertilizer (0; 400; 500; 600; 700 and 800 kg KCl/ha) on the yield and quality of Robusta coffee in Dak Lak and Kon Tum provinces from 2012-2014 showed that: Coffee trees grew well and gave the highest yield of 3.99 tons of beans/ha in Dak Lak province and 3.55 tons of beans/ha in Kon Tum province at the same dose of 600 kg KCl/ha, respectively increasing compared to the control formula without potassium chloride fertilizer by 47.3% and 49.7%, and the profit was also highest at this dose [90].
In another study by author Tran Minh Tien and colleagues (2015) on the use of potassium fertilizer in coffee farms in the Central Highlands, it was also shown that: To improve the effectiveness of potassium fertilizer for Robusta coffee trees in the Central Highlands, it is necessary to significantly reduce the amount of fertilizer during the rainy season because the ability to absorb potassium fertilizer is very limited and a significant part is washed away and lost [91].
Tassilo Tiemann and colleagues (2017) recommended the dosage of potassium fertilizer for Robusta coffee trees in the Central Highlands as follows: In the new planting year, 35 kg K 2 O/ha is needed; in the second year, 80 kg K 2 O/ha is needed ; in the third year, 105 kg K 2 O/ha is needed . During the commercial phase, coffee grown on red-brown basalt soil with a yield of > 3 tons of beans/ha needs to be fertilized from 180 to 210 kg K 2 O/ha; coffee grown on gray soil with a yield of > 2 tons of beans/ha needs to be fertilized from 155 to 180 kg K 2 O/ha. For every additional ton of beans, 60 kg K 2 O/ha needs to be fertilized [87].
According to author Nguyen Van Bo (2017), balanced and reasonable fertilization between nitrogen, phosphorus and potassium increases the efficiency of fertilizer use, fertilizing with NPK at a ratio of 200:75:250 on
On red-brown basalt soil, Robusta coffee yield reaches 2.7 tons of beans/ha/year and the efficiency of using 1 kg of NPK fertilizer is 5.14 kg of beans, increasing the efficiency of fertilizer use (23.4%). The coefficient of potassium fertilizer use (K 2 O) for coffee trees is 45 to 55%; the efficiency of using easily absorbed K 2 O from the soil is 19 to 42%. The recommended amount of potassium for commercial coffee on red-brown basalt soil in Lam Dong with a yield of 3 to 3.5 tons of beans requires 300 to 350 kg of K 2 O/ha/year. Potassium is divided into 3 fertilization times: 1st time (April to May), 30% fertilization, 2nd time (June to July), 40% fertilization; 3rd time (August to September), 30%. The balanced N:P2O5 : K2O ratio on red-brown basalt soil for Catimor variety is 2.5:1:2.5 [3] .
According to author Hoang Minh Chau (2017), each hectare of coffee needs to be fertilized with 150 to 300 kg of K2O every year , and potassium fertilizer is divided into 3 or 4 times. Potassium is essential for plants during the fruit growth and ripening stage [7].
The calculation result of the amount of K 2 O combined with N and P 2 O suitable for Robusta coffee trees on red-brown basalt soil in the Southeast and Central Highlands by author Le Minh Chau is 353 kg K 2 O + 376 kg N + 113 to 132 kg P 2 O 5 (ha/year). For every additional ton of coffee beans, 150 kg of urea + 100 kg of fused phosphate + 120 kg of potassium chloride should be added [8].
Authors Ton Nu Tuan Nam and Trinh Cong Tu (2018) recommended the dosage and form of potassium fertilizer for Robusta coffee in the business stage on red-brown basalt soil in Gia Lai province as 420 kg KCl/ha/year, KCl fertilizer is divided into 4 fertilization periods ((2nd irrigation (30 kg), early rainy season (120 kg), mid-rainy season (150 kg) and late rainy season (120 kg)) [34].
The recommendation of the Ministry of Agriculture and Rural Development (2018) on the dosage of potassium for coffee and tea gardens in the business stage after replanting in Vietnam is from 270 to 300 kg K 2 O / ha and is divided into 3 fertilization periods ((May (30% fertilization), July (30% fertilization) and September (40% fertilization)) [4].
The research results of Tran Minh Tien et al. (2020) on the effects of Polyhalite (a sedimentary mineral containing K, Ca, Mg and S) on the yield and quality of Robusta coffee in Kon Tum province from 2016-2018 showed that: Applying Polyhalite fertilizer to Robusta coffee plants gave similar results to KCl fertilizer, while Polyhalite improved the Ca, Mg, S content in plants and prevented the decline of Ca, Mg and S in coffee growing soil. The formula of Polyhalite fertilizer combined with KCl gave the best results, improved yield and quality of coffee beans, and the highest profit [92].
1.3.2. Research results on sulfur for coffee plants
1.3.2.1. In the world
The results of research on limiting factors in sandy soil for growing coffee by Lott (1960) showed that: The use of inorganic fertilizers that do not contain sulfur such as Ammonium nitrate (NH 4 NO 3 ) and Muriate of potash (KCl) on sandy soil will lead to sulfur deficiency symptoms in coffee plants [78].