U. Schulthess
Corresponding author
CIMMYT (Centro International de Mejoramiento de Maíz y Trigo), Apdo. Postal 6-641, México, D.F., CP 06600, Mexico
J. Timsina
Melbourne School of Land and Environment, The University of Melbourne, Melbourne, Vic. 3010, Australia
J. M. Herreraa
CIMMYT (Centro International de Mejoramiento de Maíz y Trigo), Apdo. Postal 6-641, México, D.F., CP 06600, Mexico
A. Mc Donaldc
CIMMYT – South Asia Regional Office, P.O. Box 5186, Kathmandu, Nepal
Yield gap analysis, Remote sensing, Ground cover, On-farm research, Maize
Crop-Soil-Water Management
Remote sensing, Productivity, Management
Study area: The study was conducted in the Rangpur district, in northwestern Bangladesh. That area is intensively cropped with rice during the rainy season. Winter (Boro) rice, potato, wheat and increasingly maize, as well as lentils, mustard, jute and other crops are grown during the remainder of the year under irrigated as well as rainfed conditions. General crop production practices for maize: Maize in Rangpur is most commonly grown in the following cropping patterns: maize–fallow–transplanted monsoon (T. Aman) rice, potato–maize/relay maize–T. Aman rice, maize–relay jute/jute–T. Aman rice, or maize–pre-monsoon (Aus) rice–T. Aman rice. In most of the areas, however, T. Aman–maize–fallow and T. Aman–potato–maize are the predominant cropping patterns. In T. Aman–maize–fallow system, maize is generally planted during November and December (called Rabi maize) and harvested during April and May, thus the growth duration of Rabi maize is around 150 days. In the T. Aman–potato–maize system, maize is sown as a relay crop 20–35 days after planting potato in January or it is grown after the early harvest of potato in late February to early March (called Kharif-1 maize), thus the growth duration of kharif-1 maize is around 110–115 days. The long duration, and hence the late variety of Rabi maize results in delay in the planting of main Kharif season rice resulting in reduced rice yield while delay in the harvesting of Kharif-1 maize results in crop damage and poor grain quality due to storm and heavy rainfall at crop maturity (Ali et al., 2008; Timsina et al., 2011). Short-duration hybrids are required in NW Bangladesh to intensify the cropping systems but they must have high yield potential too. Most maize in Rangpur is grown on deep fertile alluvial soils supplemented by large amounts of NPK fertilizer. Maize farmers apply N fertilizer rates of around 200 kg N/ha in three splits: 1/3 N as a basal dressing during land preparation, 1/3 at the 8 leaf stage and the remaining 1/3 at tasseling. Maize is planted in rows at approximately 53,000–66,000 plants/ha on conventionally tilled land. Some farmers maintain a higher plant population of up to 80,000 plants/ha. Soil ridges are made after hand weeding. Almost 100% of the maize area is planted with hybrid maize seed each year, mainly with single cross and double-cross hybrids (Ali et al., 2008). Almost all the maize is sole cropped but farmers are interested to intercrop maize with very early harvested vegetables, including potato, red-amaranth, spinach, radish, coriander and French bean. Irrigation scheduling is well developed, with around 80–85% of farmers providing the optimal 2–4 irrigations at appropriate stages of crop development. Ground truth data: In a survey maize yield data from the 2010/2011 season were collected in June of 2012 for more than 40 farmers’ fields. Additionally, sowing and harvest dates, as well as the names of varieties/hybrids, were recorded. The coordinates of one point within a field were recorded with a GPS. The yield data set was first checked for plausibility. Some fields had to be eliminated due to geo-location inconsistencies that could not be resolved. All in all, yield data from 30 fields passed the quality control. Next, field boundaries were created using a RapidEye satellite image and GoogleEarth (http://www.google.com/earth/index.html; verified October 31, 2012) as a reference. Remote sensing: An optical remote sensing image was obtained from RapidEye AG. The image had been acquired on March 26, 2011, and covered 644 km2. The native resolution of the RapidEye images is 6.5 m, but during the geo-rectification process, they are resampled to 5.0 m. The RapidEye images have five bands: blue, green, red, red-edge and NIR. The actual yield of maize for the entire study area was then calculated by applying the regression line to all the maize pixels in the image.
Field Crops Research 143 (2013) 151–156
Journal