Mapping rice-fallow cropland areas for shortseason grain legumes intensification in South Asia using MODIS 250 m time-series data
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Murali Krishna Gumma, Prasad Thenkabail, Pardhasaradhi Teluguntla, Mahesh Rao, Mohammed Ahmed, Anthony Whitbread. (4/5/2016). Mapping rice-fallow cropland areas for shortseason grain legumes intensification in South Asia using MODIS 250 m time-series data. INTERNATIONAL JOURNAL OF DIGITAL EARTH, 9 (10), pp. 981-1003.
Abstract
The goal of this study was to map rainfed and irrigated rice-fallow cropland
areas across South Asia, using MODIS 250 m time-series data and identify
where the farming system may be intensified by the inclusion of a shortseason
crop during the fallow period. Rice-fallow cropland areas are those
areas where rice is grown during the kharif growing season (June–October),
followed by a fallow during the rabi season (November–February). These
cropland areas are not suitable for growing rabi-season rice due to their
high water needs, but are suitable for a short -season (≤3 months), low
water-consuming grain legumes such as chickpea (Cicer arietinum L.), black
gram, green gram, and lentils. Intensification (double-cropping) in this
manner can improve smallholder farmer’s incomes and soil health via rich
nitrogen-fixation legume crops as well as address food security challenges
of ballooning populations without having to expand croplands. Several
grain legumes, primarily chickpea, are increasingly grown across Asia as a
source of income for smallholder farmers and at the same time providing
rich and cheap source of protein that can improve the nutritional quality of
diets in the region. The suitability of rainfed and irrigated rice-fallow
croplands for grain legume cultivation across South Asia were defined by
these identifiers: (a) rice crop is grown during the primary (kharif) crop
growing season or during the north-west monsoon season (June–October);
(b) same croplands are left fallow during the second (rabi) season or during
the south-east monsoon season (November–February); and (c) ability to
support low water-consuming, short-growing season (≤3 months) grain
legumes (chickpea, black gram, green gram, and lentils) during rabi season.
Existing irrigated or rainfed crops such as rice or wheat that were grown
during kharif were not considered suitable for growing during the rabi
season, because the moisture/water demand of these crops is too high. The
study established cropland classes based on the every 16-day 250 m
normalized difference vegetation index (NDVI) time series for one year (June
2010–May 2011) of Moderate Resolution Imaging Spectroradiometer
(MODIS) data, using spectral matching techniques (SMTs), and extensive
field knowledge. Map accuracy was evaluated based on independent
ground survey data as well as compared with available sub-national level
statistics. The producers’ and users’ accuracies of the cropland fallow classes
were between 75% and 82%. The overall accuracy and the kappa coefficient
estimated for rice classes were 82% and 0.79, respectively. The analysis
estimated approximately 22.3 Mha of suitable rice-fallow areas in South Asia,
with 88.3% in India, 0.5% in Pakistan, 1.1% in Sri Lanka, 8.7% in Bangladesh,
1.4% in Nepal, and 0.02% in Bhutan. Decision-makers can target these areas
for sustainable intensification of short-duration grain legumes.
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Whitbread, Anthony https://orcid.org/0000-0003-4840-7670