Pattern of N Mineralization and Nutrient Uptake of Tithonia diversifolia and Saccharum officinarum Leaves in Sandy Loam Soil

Bambang village is one of 13 villages in Wajak Subdistrict, Malang Regency, which known as a food crops area including maize (150 ha) and sugarcane (51 ha) (Central Bureau of Statistics, 2019). Bambang village is faced with the problem of decreasing agricultural productivity due to generally dominated by sandy soil texture and have a low soil organic C, water retention capacity, water and nutrients (Ro, 2016). The use of inorganic fertilizers continuously with an unbalanced dose will cause soil damage and environmental pollution especially on sandy soils.
       
A suitable cropping system is needed to increase the stability of crop production (Ali et al., 2021). The application of organic matter is a common practice in sustainable agriculture because soil organic matter is essential to maintain ecosystem productivity (Zhao et al., 2016). Organic matter is also one of the keys that determines soil fertility and productivity, which is the primary source of several plant nutrients, especially nitrogen (N), Phosphorus (P), sulfur (S) and most kalium (K) (Vasileva and Dinev, 2021; Dutta and Tamuly, 2021).
       
Tithonia (Tithonia diversifolia) have a fast growth cycle, high nitrogen fixation capacity and P content (Scrase et al., 2019). T. diversifolia is used as green manure because this plant contains macro and micronutrients that can improve soil fertility (Dayo-Olagbende et al., 2019). T. diversifolia can increase growth and yields of sweet corn (Hidayat et al., 2017). The use of green Tithonia fertilizer 10 t/ha gives the same results as NPK fertilization on radishes (Aboyeji et al., 2019). The use of Tithonia biomass, either alone or in combination with phosphorus fertilizers, significantly increases the efficiency of phosphorus, grain yield and maize yield components (Endris, 2019). The most widely available organic material in Bambang Village is sugarcane leaf litter, which classified as low-quality organic material, including low nutrient content, high C/N and Si ratios. Therefore, the current research aimed to analyze the pattern of N mineralization from T. diversifolia leaves and sugarcane leaves on sandyloam soils and to assess the uptake of N nutrients in maize by giving T. diversifolia leaves and S. officinarum leaves with different qualities on sandy loam soil texture.

This research was conducted at the Laboratory of Biology, Soil Chemistry and Soil Physics, Faculty of Agriculture, Universitas Brawijaya from January to May 2019 and the Greenhouse of Balitkabi Malang. T. diversifolia leaves, sugarcane leaves and soil samples for experiments were obtained around the land located in Bambang Village, Wajak District, East Java.
 
Experimental design
 
The incubation experiment carried out using non-leaching incubation method. Treatments was randomly divided into 6 group (n=4): 100% T. diversifolia leaves (T1); 100% sugarcane leaves (T2); 75% T. diversifolia leaves and 25% S. officinarum leaves (T3), 50% T. diversifolia leaves and 50% S. officinarum (T4), 25% T. diversifolia and 75% S. officinarum leaves (T5) and control (T6). Each treatment was mixed with 100 g of soil (sandy loam texture, diameter<2 mm, air dry) and added with water until 70% of the soil’s water holding capacity. All bottles are covered with aluminium foil and given a small hole to reduce evaporation and keep aeration at ± 26°C. During the incubation period, the water content is maintained at 70% of the capacity of the soil to hold water by weighing the bottles periodically.
 
Greenhouse research
 
Sandy loam texture soil weighing 10 kg (top layer 0-20 cm, dry wind, passing 2 mm sieve) is mixed evenly with each treatment then put in a plastic bucket and incubated for 2 weeks while maintaining soil moisture at field capacity. After incubation, 3 pertiwi maize seeds were planted in a plastic bucket. Each pot was given a basic fertilizer of 300 kg urea/ha, 100 SP-36 kg/ha and 75 kg KCl/ha. During the experiment, water was given every day and N nutrient uptake of corn plants was observed by harvesting corn at its maximum vegetative growth.
       
The characteristics of soil and organic matter used in this experiment are as follows: pH H₂O=5.1, pH KCl=4.9, organic C=1.89%, N-total=0.19%, C/N=10, total P (/Bray) =5.87 mg/kg, K=0.16 me/100 g, Na=0.05 me/100 g, Ca=3.80 me/100 g, Mg=1.37 me/100 g, CEC=23.06 me/100 g, base saturation (KB)= 3%, N-NH₄=2.10 mg/kg, N-NO₃=14.31 mg/kg body weight, BI=1.07 g/cm³, specific gravity=2.25 g/cm³, porosity=52.4%, moisture content pF 2.5=26%, KA pF 4.2=7%, soil texture sandy loam with content sand=70%, dust=20% and clay=10%.
       
The characteristics of the organic material used were as follows: C-organic T. diversifolia leaves=28.08%, N-total =4.17%, C/N ratio=7.02, P=0.41%, K=3.62%, polyphenols =7.82%, lignin=8.89%, Ash=1,8%, Cellulose= 15.92%, L/N=2.14, L+P/N=4,03. The characteristics of S. officinarum leaves are C-organic=35.01%, N-total= 1%, C/N ratio=39.35, P=0.15%, K=1.23%, polyphenols=6.69%, lignin=24.26%, cellulose=34.14%, L/N=27.18, L+P/N=34.69%.
 
Data collection
 
Data were collected at 1, 2, 4, 6, 8, 10 and 12 weeks destructively on 168 sample bottles. Soil samples for NH₄⁺ and NO₃^- analysis were immediately analyzed under humid conditions, chemical analysis of soil was carried out by freeze drying and weighing. Determination of NH₄⁺ and NO₃^- levels was carried out by extracting the soil with the distillation method using KCl 1N+HCl 0.1N; then the extract was analyzed by the Distillation method. Soil pH consisting of pH H₂O and pH KCl (1:1) was analyzed using a pH meter, organic C, total N used the Kjeldahl method. Total P was measured using a spectrophotometer, K was measured using atomic absorption spectrophotometry, cation exchange capacity (NH₄OAC pH 7.0) (Indonesian Soil Research Institute, 2012).
 
Statistical analysis
 
Observation data were analyzed for variance at the confidence level of 95% (α=5%) and if there was a significant effect, Duncan’s continued test was carried out at the 5% level. All analyzes were performed with the Genstat program.

Mineral N-cumulative released
 
The combination of tithonia and sugarcane leaves had a significant effect on the cumulative N release in sandy loam soils. In general, T1 treatment released the highest cumulative N at each observation time. The cumulative N-release from the T3 and T4 treatments showed the same pattern until the 4^th week (Fig 1). The amount of Mineral N released in each treatment was 54.58-529.7 mg/kg (T1), 41.80-381 mg/kg (T2), 47.69-473.6 mg/kg (T3), 46.70-424.0 mg/kg (T4), 70.69-378.9 mg/kg (T5) and 47.14-303.6 9 mg/kg (T6). The amount of N released into the soil increased after treatment with large amounts of tithonia. This indicates that mixing organic matter derived from tithonia with a low C/N ratio with organic matter from sugarcane leaves which has a high C/N ratio can increase the rate of soil mineralization compared to organic matter from sugarcane leaves alone, due to the reduced C/N ratio.
 

       
The decomposition and release of N from organic matter were partly related to the biochemical composition of the material, in addition to the residual N concentration, the C/N ratio and the lignin content of the material (Sholihah et al., 2012). The N content of tithonia (4.17%) higher than sugarcane leaves (1 %) was one of the factors that cause the fast release of N from tithonia and the amount was more than with sugar cane leaves alone. Vahdat et al., (2011) states that the level of N mineralization is positively correlated with the residual concentration of N. N mineralization was influenced by the C/N ratio, organic matter that has a low C/N ratio results in a higher mineralization rate compared toorganic matter with a high C/N ratio (Abera et al., 2012). Organic matter which had a high C/N ratio will inhibit N mineralization due to a large amount of carbon and higher levels of N decomposition, causing nitrogen to be suppressed in the amended soil.
 
N mineralization rate
 
The constant rate of N mineralization at all observation times indicated that the application of tithonia and sugarcane leaves had a significant effect on the rate of mineralization. The highest mineralization speed at all observation times was found in T1 and the lowest in control. Tithonia undergoes mineralization faster than sugarcane leaves (T2) and the higher the amount of tithonia in the mixture, the faster the mineralization occurs compared to only sugarcane leaves (Fig 2).
       

 
The amount and rate of N mineralized depend on environmental factors, particularly humidity and temperature. This temperature and humidity affect the growth of soil microorganisms which are responsible for the breakdown of organic matter. The decomposition of organic matter will be faster at high temperatures (Yuan et al., 2016). Optimal mineralization occurs at higher temperatures (24-30°C) and water content of 100% field capacity. The incubation was set at the same temperature and humidity; it was assumed that the mineralization rate constant (k) was more influenced by the chemical composition of the added organic matter. The highest k value was found in the treatment of 100% tithonia/T1 (0.02623) and the lowest in control/T6 (0.02162) in each week. In general, the control treatment for mineralization constants was lower than that with the addition of organic matter. This was due to the absence of the addition of organic matter which performed as an energy source for soil microorganisms. The number of microbes in the soil with a low, low organic matter content would inhibit the rate of N mineralization (Abera et al., 2012).
       
In general, the pattern of NH₄⁺ and NO₃^- released in the combination treatment of tithonia and sugarcane leaves fluctuated every week (Fig 3). The amount of NH₄⁺ in each treatment is: T1 = 18.32 -118.0 mg/kg, T2 = 16-155.4 mg/kg, T3 = 14.25-124.9 mg/kg, T4 = 16.42-126.0 mg/kg, T5 = 25.49-143.7 mg/kg and T6 = 12.48- 104.1 mg/kg. The administration of tithonia and sugarcane leaves could increase NH₄⁺ compared to the control for 12 weeks. The largest increases in NH₄⁺ was found in T2 group. The combination of tithonia leaves and sugarcane leaves withthe same proportion (T4) gave the same effect a combination of 75% tithonia leaves; 25% sugarcane leaves (T3).
 

       
Based on Fig 3, the highest NO₃- release was found in 100% tithonia (T1) treatment and the lowest was in 100% sugarcane leaf treatment and control treatment. The amount of NO₃- released in each treatment was T1=36.26-411.7 mg/kg, T2=25.81-226.4 mg/kg, T3=33.44-348.7 mg/kg, T4=30.28-298.1 mg/kg, T5=39.42-234.8 mg/kg and T6=34.46-199.5 mg/kg. Treatment with a higher amount of tithonia releases N faster than the other combinations. The amount of N released to plants depends on the organic chemical composition such as N content, C/N ratio, cellulose and hemicellulose content, polyphenols (Mohanty et al., 2011) and also depends on pH, moisture and soil temperature (Biswas et al., 2016).
       
The application of T. diversifolia leaves and its combination with sugarcane leaves significantly affected N nutrient uptake in corn (Fig 4). T1 group significantly increased N uptake compared to T2, T6 and control group (T7). The increase in N uptake due to giving 100% tithonia leaves was 81.51%, 83.12% and 144.54% compared to T2, T6 and control. T4 group significantly increased the N uptake by 78.29%, 76.86% and 140.18% compared to T2, T6 and control. 75% combination of tithonia leaves; sugarcane leaves 25% significantly increased N nutrient uptake by 67.74%, 69.22% and 125.98% compared to T2, T6 and T7 group, while the combination of tithonia leaves 25%; sugarcane leaves 75% significantly increased N uptake by 73.74%, 75.27% and 134.06% compared to T2, T6 and T7. T2, T6 and T7 groups gave the same effect on N nutrient uptake in corn plants.
 

       
The increase in N nutrient uptake due to administration of 100% tithonia leaves and a combination of tithonia leaves and sugarcane leaves compared to controls was 125% to 144.54%. Based on the N content in the organic material used, it shows that tithonia has the highest N compared to sugarcane leaves and the combination of tithonia leaves and sugarcane leaves, the N content in tithonia is (4.17%), sugarcane leaves (1.00%), T3 (3.37%), T4 (2.53% and T5 (1.42%). This may be one of the causes of the high N uptake in the 100% tithonia leaf treatment compared to other treatments. The application of tithonia leaves and sugarcane leaves had a significant effect on the cumulative N release compared to the control, as well as the N uptake in plantsmaize, which showed that the highest N uptake was found in T1 treatment which also released the highest N nutrient.

The cumulative N mineral release pattern was significantly influenced by the organic matter of tithonia (T. diversifolia) and sugarcane (S. officinarum) leaves and the combination of both. Application of tithonia leaves and sugarcane leaves on sandy loam soil texture significantly affected N nutrient uptake in maize. N uptake in maize increased by 125.98% to 144.54% compared to control.

This study financially supported by BUDI-DN LPDP Indonesia. The gratitude is also addressed to the technicians from the Laboratory of Soil Chemistry, Laboratory of Soil Physics, Faculty of Agriculture, Universitas Brawijaya. Highest appreciation to the Promoter Team for their guidance in writing this article.