Debtanu Maiti

Management of nitrogen through the use of Leaf Colour Chart (LCC) and Soil Plant Analysis Development (SPAD) in wheat under irrigated ecosystem

Abstract A field experiment was conducted in a farmers field in the district of Nadia in West Bengal, India, to study the management of nitrogen (N) through leaf colour chart (LCC) and soil plant analysis development (SPAD), based on chlorophyll meter in wheat (cv. UP-262). During the dry seasons of 2001 – 2002 and 2002 – 2003. Treatment combinations were taken based on different levels of N at fixed-schedule and through LCC and SPAD. The experimental soil (0 – 15 cm) had pH, 7.33; organic C, 0.43%; available N, 408.70 kg ha−1; available P, 6.92 kg ha−1 and available K, 66.31 kg ha−1. The results of LCC and SPAD or chlorophyll meter for the nitrogen management in wheat show that values of both LCC and SPAD significantly increased with an increasing level of N. The mean values of LCC and SPAD varied from 3.14 – 5.14 and 26.52 – 37.00, respectively in wheat. The results show that the amount of N can be preserved as 40 – 67.5 and 57.5 – 72.5 kg ha−1 through the use of LCC and SPAD in wheat over the fixed timing N treatment T7 where 150 kg N ha−1 was applied in three splits without reduction in the yield. The SPAD and LCC-treated N plot showed higher N-use efficiency over fixed-scheduling N treatment in wheat. The results further show that the SPAD value of 37 and LCC value of 5 are better than SPAD (35) and LCC (4) for the best management of N in wheat in an Inceptisol.

Simulation of fertilizer requirement for irrigated wheat in eastern India using the QUEFTS model

Abstract Crop modelling can provide us with a vast amount of real-time information about fertilizer dose to achieve the target yield, crop conditions, etc. Nutrient-use efficiency in wheat is low because of conventional blanket and imbalanced fertilizer use. Estimation of fertilizer requirements based on quantitative approaches can assist in improving yields and nutrient-use efficiency. Field experiments were conducted in 20 sites in eastern India to assess the soil supply, requirement and internal efficiency of nitrogen (N), phosphorous (P), potassium (K) and zinc (Zn) in wheat. The data were used to calibrate the QUEFTS (QUantitative Evaluation of the Fertility of Tropical Soils) model for site-specific, balanced fertilizer recommendations. The parameters of maximum accumulation (a) and maximum dilution (d) in wheat were calculated for N (35 and 100 kg), P (129 and 738 kg), K (17 and 56 kg), and Zn (21502 and 140244 mg). Grain yield of wheat showed good correlation with N (R2 = 0.937**), P (R2 = 0.901**) and K uptake (R2 = 0.801**). The NPK ratio to produce 1 ton grain yield of wheat was derived to be 4.9:1.0:8.9. The relationships between chemical properties and nutrient supplying capacity of soils were also established. The model was validated using the data of four other experiments. Observed yields with different amounts of N, P, K and Zn were in good agreement with the predicted values suggesting that the validated QUEFTS model can be used for site-specific nutrient management in wheat.

Influence of pH on Soil Charge Characteristics and Cadmium Sorption in Some Noncontaminated Soils of Indian Subtropics

Concentrations of total dissolved cadmium (Cd) and activity of its free ions in soil solution are suggested to be influenced by soil pH, organic matter (OM) content, cation exchange capacity (CEC), and clay mineralogy. We investigated the sorption of Cd by taking 25-, 50-, and 100-µM Cd solutions in five noncontaminated soils of West Bengal, India, having differing chemical properties with batch sorption experiments. The charge characteristics and point of zero salt effect (PZSE) of all experimental soils were calculated by the potentiometric titration method measuring the adsorption of H+ and OH– on amphoteric surfaces in solutions of varying ionic strength (I). Sorption of Cd was more pronounced at pH levels greater than PZSE for all experimental soils. The CEC, OM content, clay mineralogy, and specific surface area (SSA) also had a great influence on the sorption of Cd from soil solution to soils. The relationships of Cd with those parameters were found to be consistent and the results concluded that Cd sorption in soils is strongly affected by the soil characteristics.

Evaluation of different analytical methods for the estimation of available N, P, K and Zn in soil

Abstract Different chemical methods were tested to measure the available nitrogen (N), phosphorous (P), potassium (K), and zinc (Zn) in rice-wheat soils. The results show that the available N extracted by alkaline KMnO4 was highest (429.24 kg ha−1) followed by 4 M KCl (233.35 kg ha−1) and aerobic incubation (with a mean value of 83.63 kg ha−1). The Mehlich-3 extracted P on an average 12% more than Olsens P and 98.92% more than Bray-I method. The available K extracted by Mehlich-3 method was highest (86.81 kg ha−1) followed by NH4OAC (83.93 kg ha−1) and CaCl2 (76.59 kg ha−1). The results also record that the Mehlich-3 extracted on average 114.04% more Zn than 0.005 M DTPA and 31.18% more than 0.1 N HCl extraction methods. The results highlight that the 0.1 N HCl extracted on average 63.16% more Zn than 0.005 M DTPA extraction method. The highest correlation of coefficient (r) for the estimation of available N, P, K and Zn were alkaline KMnO4 vs. aerobic incubation (0.972**); Mehlich-3 vs. Olsens P (0.994**); Mehlich-3 vs. NH4OAC (0.995**) and Mehlich-3 vs. 0.1 N HCl (0.615**).The results suggest that alkaline KMnO4 and Mehlich-3 method of extraction are superior for the estimation of mineralisable N and available P, K and Zn from soils as shown by the ‘r’ values.

Simulation of fertilizer requirement for irrigated wheat in Eastern India using the QUEFTS model

Crop modeling can provide us with information about fertilizer dose to achieve the target yield, crop conditions, etc. Due to conventional and imbalanced fertilizer application, nutrient use efficiency in wheat is low. Estimation of fertilizer requirements based on quantitative approaches can assist in improving yields and nutrient use efficiency. Field experiments were conducted at 20 sites in eastern India (Nadia district of West Bengal) to assess the soil supply, requirement, and internal efficiency of N, P, K, and Zn in wheat. The data were used to calibrate the QUEFTS (Quantitative Evaluation of the Fertility of Tropical Soils) model for site-specific, balanced fertilizer recommendations. The parameters of maximum accumulation (a) and maximum dilution (d) in wheat were calculated for N (35, 100), P (129, 738), K (17, 56), and Zn (21502, 140244). Grain yield of wheat showed statistically significant correlation with N (R2 = 0.937**), P (R2 = 0.901**), and K uptake (R2 = 0.801**). The NPK ratio to produce 1 tonne grain yield of wheat was calculated to be 4.9:1.0:8.9. The relationships between chemical properties and nutrient-supplying capacity of soils were also established. The model was validated using the data from four other experiments. Observed yields with different amounts of N, P, K, and Zn were in good agreement with the predicted values, suggesting that the validated QUEFTS model can be used for site-specific nutrient management of wheat.