An experiment was conducted on BARI Central Research Station, Gazipur during rabi season of 2019-2020. The initial soil samples at a depth of 0-15 cm from the experimental fields were collected and analyzed following standard methods. The experiment was laid out in a randomized complete block design with three replications in each treatment. Four different treatments viz. T1: N-control, T2: RD of nitrogen (225 kg ha-1) in the form of Prilled urea, T3: Application of 200 kg nitrogenha-1 in the form of urea super granule (USG), T4: Application of 205 kg nitrogenha-1 in the form of neem coated urea were selected for different plots randomly. Properties of different form of urea are presented.
For prilled urea, 1/3rdof urea is applied before sowing as basal. Remaining 2/3rd urea is applied in two installments as broadcast; one at 40 days after sowing another at 75 days at sowing. For neem coated urea, ½ of urea is applied before sowing as basal. Remaining ½ urea is applied as broadcast at 40 days after sowing. For USG, whole urea are applied as band placement during sowing in between two maize rows at 10 cm apart. P, K, S, Zn & B were applied @ 60, 110, 40, 4 & 1.4 kg ha-1. P-K-S-Zn-B was supplied from TSP, MoP, gypsum, zinc sulphate and boric acid, respectively. All PKSZnB were applied at the time of final land preparation. The unit plot size was 4m x 3m. The tested crop was BARI Hybrid Maize-9. Maize was sown 60 cm line to line and 20 cm plant to plant. Maize seeds were sown first week of December, 2019. All the intercultural operations such as irrigation, weeding, insect control etc. were done as and when necessary.
Harvesting of maize was done on April 2019.Ten plants from each plot were tagged at random to take records on different agronomic parameters of maize. Data on yield and yield contributing parameters were recorded and statistically analyzed with the help of statistical package Crop-Stat and mean separation was tested by Least Significance Difference (LSD) (Steel and Torrie, 1960). Post harvest soil and plant samples were also collected and analyzed.
Nutrient use efficiency :
A. Agronomic use efficiency (AE) :
Agronomic efficiency refers to the increase in crop yield per unit of an applied nutrient. It can be calculated as follows:
AE = (YNA-YN0)/NRN
Where,
AE : Agronomic efficiency
YNA : Yield (kg ha-1) due to nutrient addition
YNO : Yield (kg ha-1) due to nutrient omission
YRN : Rate of nutrient addition (kg ha-1)
B. Recovery Efficiency (RE) :
Recovery Efficiency (RE) refers to the increase in nutrient uptake by plants per unit of an applied nutrient. It can be calculated as follows:
RE = (NUNA-NUN0)/NRN
Where,
RE : Recovery efficiency
NUNA : Nutrient uptake (kg ha-1) due to nutrient addition
NUNO : Nutrient uptake (kg ha-1) due to nutrient omission
YRN : Rate of nutrient addition (kg ha-1)
Methods of chemical analyses:
Soil pH was measured by a combined glass calomel electrode (Jakson, 1958). Organic carbon was determined by wet oxidation method (Walkley and Black, 1934). Total N was determined by modified Kjeldahl method. Ca and Mg were determined by NH4OAc extraction method. K, Cu, Fe, Mn and Zn were determined by DTPA extraction followed by AAS reading. Boron was determined by CaCl2 extraction method. Phosphorus was determined by Bray and Kurtz method (Acid soils). S was determined by CaH4 (PO4)2.H2O extraction followed by turbidimetric method with BaCl2.