CHAPTER INTRODUCTION 1.1 Rationale Sugarcane (Saccharum officinarum L.) is an annual crop producing the most biomass then it requires a large amount of nutrient inputs for its life cycle There are some methods to assess nutrient status of sugarcane in order to determine correct rate of fertilizer, such as: (i) the Critical Nutrient Concentration (CNC) method has developed table of critical nutrient value and optimum range of sugarcane leaf that is considered as standard for diagnosis; however, this way will be not precise when other nutrient concentrations vary in tissue (Walworth and Sumner, 1986; Bailey, 1989, 1991 and 1993); (ii) the Diagnosis and Recommendation Integrated System (DRIS) is suggested by using at least ratios (normally to 7) of nutrient concentration for diagnosis (Walworth and Sumner, 1987) The DRIS has been applied successfully to explain result of leaf analysis in many kinds of crops, including sugarcane (Beaufils and Sumner, 1976; Elwali and Gascho, 1984; Beverly, 1991; Reis, 1999 and Hundal et al., 2005) Nevertheless, it seems to be as a “qualitative method” by showing “lack or excess of nutrients” situation but not providing fertilizer application rates to crop; (iii) the Site-Specific Nutrient Management (SSNM) is based on crop yield at a particular plot gained from two main sources: soil nutrient-supplying capacity and fertilizer application Determining amount of fertilizer input will reduce nutrient loss on one hand and improve fertilizer use efficiency on the other hand The SSNM approach has been applied successfully for rice crop (Dobermann et al., 2002) and hybrid corn over the world (Pasuquin et al., 2014), but the application for sugarcane is limited Besides the need to determine fertilizer rate, timing of fertilization for increasing nutrient use efficiency by crops need to be considered as well Using leaf colour chart (LCC) to diagnose nitrogen content in crop was considered a simple, easy method and have been popularly applied to rice However, the study of LCC in sugarcane is still limited 1.2 Research objectives (i) To assess current sugarcane farming and use of NPK fertilizer in alluvial (Soc Trang province) and acid sulfate soils (Hau Giang province) (ii) To determine effect of NPK fertilizer inputs to the nutrient uptake, growth and yield of sugarcanes under the two soil types (iii) To determine recovery efficiency (RE) and agronomic efficiency (AE) in order to suggest NPK application for sugarcane cultivation (iv) To evaluate LCC application for nitrogen timing on sugarcanes in two soils 1.3 Object and scope of research • Object of research: NPK application for sugarcane (Saccharum officinarum L.) • Scopes of research:  Field experiments were carried out on sugarcane farmers in Cu Lao Dung district of Soc Trang province and Long My district of Hau Giang province  Research period: January 2011 to January 2013  Omission plot experiments were implemented to evaluate the omission of N, P, K nutrients  Study on growth and N, P, K uptake of sugarcane aims at improving scientific knowledge having a database for calculating “soil nutrient-supplying capacity” and fertilizers rate to achieve “target yield” based on SSNM principle 1.4 Limitations of research • About fertilizer: only study N, P, K nutrients by inorganic fertilizer for sugarcane; the sugarcane pressmud was introduced as “improved treatment” according to the SSNM recommendation • About location and experimental design: to minimize variation in statistical analysis, the experiments were designed as randomized completely block with replications at two soil conditions The research did not apply “on-farm research” in several locations as recommended by SSNM • About soils: limited in two soil types in the Mekong delta such as: (i) alluvial soil (Dystric Fluvisols) in Cu Lao DungSoc Trang and acid sulfate soil (Thionic Gleysols) in Long My-Hau Giang 1.5 Scientific and practical significances + Scientific significance This study is based on the principle of SSNM Fertilizer recommendation for small scale where soil, crop, climate, weather, cultural practice should be the same Therefore, recommendation based on crop need at specific field will get higher fertilizer use efficiency Principally, calculation of fertilizer rates based on the SSNM method comes from nutrient balance which is manifested by crop yield According to this approach, there are two sources of nutrient, such as soils and fertilizers to create optimum yield of crop In this research, NPK fertilizer rates have been extrapolated based on the difference between sugarcane nutrient requirements and the soils nutrient supplying capacity In addition, the database on growth and nutrient uptake of sugarcane in Mekong delta soils has been constructed in this study, which would be useful to assess crop growth and nutrient balance on the sugarcane soils + Practical significance The results can be applied for sugarcane farming in the Mekong delta By simple and easy practice, the study results help to reduce production costs then increase price competition in the region In the coming crops, determination of NPK fertilizers rates can be updated by extension workers or farmers through “omission plot technique” at some representative sugarcane fields in the Mekong delta The result from LCC application for sugarcane is important reference to help farmers estimate when to test leaf color and apply nitrogen exactly as crop need in the two soil types 1.6 Innovativeness - SSNM and LCC have been applied first time in the Mekong delta, the results showed that the method is helpful for determining NPK fertilizers rates and nitrogen application timing for sugarcane in the Mekong delta - Soil-supplying capacity of N, P, K for sugarcane have been determined Percent ratio of N, P, K from soils to total crop requirement in order to achieve target yield were recorded as 32.6%N, 46.2%P2O5, 56.1%K2O in Cu Lao Dung and 32.9%N, 59.6% P2O5 63.4% K2O in Long My - At the same NPK fertilizer application rates, response to sugarcane yield in Long My was about 89% compared to Cu Lao Dung Using “improved treatment” by using sugarcane pressmud at 10 tons/ha made sugarcane yield increased at both study sites - Farmers in the research areas almost have not applied K for sugarcane The application of potassium made Brix degree of sugarcane increased in both Cu Lao Dung and Long My CHAPTER LITERATURE REVIEW 2.1 Sugarcane farming in Soc Trang and Hau Giang Soc Trang and Hau Giang are located in the lower Mekong delta According to Hua Thanh Xuan (2008), Soc Trang is one of the largest sugarcane producers in the Mekong delta in term of planted areas Most sugarcanes are planted in the island of Cu Lao Dung and Long Phu formed by alluvial deposition Currently sugarcane yield in Cu Lao Dung is higher than average of the world Hau Giang has the highest ranks of sugarcane planted area as well as production in the Mekong delta, annual planted area of sugarcane in Hau Giang is situated after rice with 13,063 and yield of 82,60 tons per (Statistical Year Book, 2010) 2.2 Botanical requirement characteristics, growth and nutrient 2.2.1 Botanical characteristics of sugarcane 2.2.2 Periods of growth 2.2.3 Nutrient requirement Sugarcane is a long crop that belongs to C pathway creating big amount of production and needs high humidity, nutrients, sunshine to optimize its productivity It is estimated that one ton of sugarcane production requires 0.56-1.20 kgN, 0.38-0.82 kgP 2O5, 1.00-2.50 kgK2O, 0.25-0.60 kgCa, 0.20-0.35 kgMg, 0.02-0.20 kgNa and 2.0-2.7 kgS together with micronutrients (Zender, 1990) On average, one sugarcane crop takes away 208, 53, 280, 30, 3.4, 1.2 and 0.2 kg N, P, K, S, Fe, Mn and Cu respectively from soils to achieve yield of 100 tons per (Singh and Yadav, 1996) Nutrient requirements are different by soil conditions from place to place (Natesan et al., 2007) 2.2.4 Quality parameters of sugarcane 2.3 Characteristics of K88-92 sugarcane variety 2.4 Fertilizer 2.4.1 Fertilizer recommendation for sugarcane Fertilizer is the most important factor of nutrient supply for sugarcane, accounting for about 50% of yield increase Fertilizer recommendation is higher in the tropical than sub-tropical regions Saini et al (2006) recommended fertilizer for sugarcane production as 400 kgN, 170 kgP and 180-190 kgK depending on time and soil conditions 2.4.2 Role of N, P and K 2.4.2.1 Nitrogen (N) Nitrogen is a key nutrient affecting yield and quality of sugarcane Nitrogen increases sugarcane yield through increases of shoots, stalk height, diameter of internode (Abayomi, 1987) Seasonal nitrogen use efficiency is estimated at 0.841 tons sugarcane kg-1N (Chattopadhyay et al., 2004) Quantity of nitrogen fertilizer in the world ranges from 50 to 300 kgN -1 and kg of nitrogen can create 0,5-1,2 tons ha-1 (Hunsigi, 1993) 2.4.2.2 Phosphorous (P2O5) Phosphorus is an essential element to promote creation of roots and increase of branches but its availability depends on local soils and fertilizer application Increase of sugarcane yield after phosphorus use is results of sucker development, biomass, and density At optimum phosphorous level, sugar concentration and juice purity are also better (Elamin et al., 2007) 2.4.2.3 Potassium (K2O) Potassium nutrient plays important roles in plant growth and metabolism Potassium fertilizer application often increases sugar concentration and juice return, especially the case of late harvest (Hunsigi, 2011) 2.5 Site-specific Nutrient Management approach 2.5.1 Definition Site-specific nutrient management (SSNM) is an approach to feeding crop with nutrients as and when needed The application and management of nutrients are dynamically adjusted to crop needs of the location and season This method helps farmers adjust fertilizers to address lack of nutrients between required nutrients to maximize crop yield and nutrient reserve of the soils, organic materials, and irrigation water The SSNM approach aims to increase farmers profit through higher yield, application of nutrients (mainly N, P and K) locally and seasonally, and optimal use of existing indigenous nutrient source such as crop residues and organic fertilizers 2.5.2 Principles of SSNM 2.5.2.1 Principles of SSNM According to Witt et al (2006) the SSNM provides maize farmers knowledge to maximize fertilizer use and profit by balance of required nutrients for high yield and indigenous nutrient supply from soils, organic matters, crop residues, fertilizers and water This new method is based on model of QUEFTS (Quantitative Evaluation of the Fertility of Tropical Soils) developed in Africa for maize crop (Janssen et al., 1990; Smaling Janssen, 1993) and later for rice crop (Witt et al., 1999; Wang et al., 2001; Dobermann et al., 2002) Technology of omission plots is useful to determine fertilizers required to meet target yield (Witt and Doberman, 2002) In this method N, P and K fertilizers are applied in sufficient amounts to overcome deficiencies and ensure high yield The target yield can be determined from plots without limitation of NPK In other words, the SSNM is an approach based on the plant that utilizes the omission plot technique to determine the yield obtained with only the soil reserves (omission plots) compared to the attainable yield obtained when nutrients are not limiting 2.5.2.2 Steps of SSNM Step 1: Determine target yield Step 2: Estimate soil nutrient-supplying capacity Step 3: Calculate N, P and K nutrient inputs to meet deficiencies between crop need and soil supply 2.5.2.3 Parameters in the SSNM 2.5.3 Agronomic efficiency of N, P and K Agronomic efficiency of N, P or K (AEN, AEP or AEK) is the increase in yield per unit of fertilizer N, P2O5 or K2O applied Fertilizer recommendation based on yield response and agronomic efficiency is an alternative approach where soil testing is not used regularly This sounds good approach compared to other supportive decision making tools 2.5.4 Use of “improved treatment” in SSNM for sugarcane 2.5.5 Managemnet of nitrogen in sugarcane farming 2.5.5.1 Determine timing to apply nitrogen fertilizer 2.5.5.2 Manage nitrogen nutrient to balance supply and demand 2.5.5.3 Diagnose nitrogen by LCC technique Leaf color is considered as an indicator to diagnose requirement of nitrogen fertilizer for crop Previous studies show that rice genotype and nitrogen management based on LCC affected yield and yield components (Nagappa et al., 2002) Farmers believe that when the leaves shift from dark to light green or yellow, crop needs more nitrogen Similarly, LCC is applied for sugarcane too (Gaddanakeri et al., 2007) Chandrashekara (2009) reported that application of nitrogen at 50 and 60 kgN/ha with LCC=6, sugarcane yields were high (150.5 and 151.7 tons/ha in the first crop and 123.8 and 125.0 tons/ha in the second crop respectively), CCS, juice, Brix, Pol and fructose, total uptake of N, P, K less than traditional practice 2.6 Method of soil nutrient assessment in sugarcane 2.7 Nutrient interaction in sugarcane farming CHAPTER RESEARCH METHODOLOGY This study consists of four main activities: 3.1 Activity 1: Survey on current sugarcane farming and fertilizer application in the research areas Household survey was conducted in sugarcane areas of Cu Lao Dung (Soc Trang) and Long My (Hau Giang) districts to understand farming techniques such as veriety, quantity of fertilizer use, yield 3.2 Activity Study effects of fertilizers on sugarcane growth, NPK uptake, and yield This is a factorial experiment in a randomized complete block design with factors, replications, and treatments as NPK, NP, NK, PK and NPK, NP, NK, PK in combination with sugarcane pressmud in Cu Lao Dung (Soc Trang) and Long My (Hau Giang) to assess effects of nutrient omission application (N, P, K) and sugarcane pressmud to growth, nutrient uptake, and yield of sugarcane The experiment was carried out from January 2011 to January 2012 3.3 Activity Determine return efficiency (REX) and agronomic efficiency (AEX) to recommend fertilizer (N, P, K) application for sugarcane There were two field experiments including sugarcane cultivated by planting (January 2011 to January 2012) and by ratooning (January 2012 to December 2012) which is a practice of growing a crop from the stubbles of previous crop at the same field in Activity to determine AE and RE for NPK fertilizer recommendation of sugarcane at two research sites 3.4 Activity Diagnose for nitrogen application timing by LCC technique The experiment was randomized complete block design with replications and four treatments as PPB-1, PPB-2, PPB-3 and PPB-4 in Cu Lao Dung-Soc Trang and Long My-Hau Giang (Table 3.5) The experiment was carried out from January 2012 to January 2013 to diagnose timing for nitrogen application by LCC technique Table 3.5: Treatment of nitrogen application timing Treatment PPB-1 PPB-2 PPB-3 PPB-4 Nitrogen application timing (Day after cultivation) 10-20 60 90 120 150 1/5 1/5 1/5 1/5 1/5 1/5 1/5 2/5 LCC LCC 1/5 1/5 LCC Weekly measurement, applied N when LCCK (a) (b) Figure 4.13: Increase of sugarcane yield (tons/ha) when NPK application at level of 300-125-200 kg/ha in combination with sugarcane pressmud at 10 tons/ha: (a) Cu Lao Dung and (b) Long My, plant cane crop 2011-2012 and ratoon 2012 16 4.3.1.2 Determine agronomic efficiency (AE X) and return efficiency (REX) to recommend fertilizer (N, P, K) application for sugarcane at alluvial and acid sulfate soils a) Agronomic efficiency (AEX) of N, P, K fertilizers In Cu Lao Dung alluvial soils, agronomic efficiency of nitrogen (AEN) was 0.15; it means that increase kg of nitrogen will increase 150 kg of sugarcane Similarly, agronomic efficiency of phosphorus (AEP) was 0.14 and agronomic efficiency of potassium (AEK) was only 0.05 In Long My acid sulfate soils, the agronomic efficiency was lower with AEN, AEP, AEK was recorded as 130 kg sugarcane/kgN, 100 kg sugarcane/kgP2O5 and 50 kg sugarcane/kgK2O respectively Pressmud application did not increase AEx at both study sites b) Recovery efficiency (REX) of N, P and K In Cu Lao Dung, over the two crops the recovery efficiency of nitrogen (REN) was 49%, phosphorous (REP) 33% and potassium (REK) 93% In combination with pressmud, the recovery efficiencies of N, P, K were recorded as 37, 17 and 53% respectively In Long My, the recovery efficiency of nitrogen (RE N) was 48%, phosphorous (REP) 45% and potassium (REK) 77% In combination with pressmud, the recovery efficiencies of N, P, K were recorded as 43, 13 and 82% respectively 4.3.2 Estimate fertilizers for sugarcane in Cu Lao Dung alluvial soils and Long My acid sulfate soils Based on the household survey in Cu Lao Dung (Soc Trang) and Long My (Hau Giang) presented in Table 4.10, sugarcane yield in Cu Lao Dung (158 tons/ha) and Long My (135 tons/ha) were considered as target yield to estimate nutrient inputs for the two sites NPK fertilizer application were estimated according to Pasuquin et al (2014) with AEN, AEP, and AEK have been calculated above (section 4.3.1.2, part a) Thus, NPK application was recommended as 328N-156P2O5-279K2O (kg/ha) in Cu Lao Dung and 334N-168P2O5-296K2O (kg/ha) in Long My 17 4.4 Activity Diagnose nitrogen application timing for sugarcane by LCC application 4.4.1 Effect of nitrogen application timing on Brix degree Table 4.46 showed that nitrogen application methods affected Brix degree of sugarcane cultivated in Cu Lao Dung at 330 days after cultivation The highest Brix degree (21.5%) was recorded at PPB-4, used nitrogen when LCC