Employing Phenology to Delineate Wheat Agro-Climatic Zones in Afghanistan

Afghanistan grows wheat on about 2.5 million hectares with an average annual production of about five million tonnes. The local research and development efforts make use of country wide research results to recommend varieties and other technologies. Afghanistan has wide ranging climatic variability and its wheat acreage therefore needs to be delineated into wheat climatic zones. A set of 10 different types of wheat varieties were scored for average number of days to 50% flowering (ADF) at 10 locations to delineate Afghan wheat acreage into homogeneous wheat climatic zones based on ADF values. The results obtained hinted at creating eastern, northern, south western and a highland zone for conducting research and recommending wheat technologies.


Introduction
Afghanistan is a wheat eating country where per capita wheat consumption stands at over 200 kg/annum.Wheat is a staple food as it provides over 60% of daily caloric requirement of an average Afghan (Persaud, 2012).Decades of war have inhibited growth of both research and development in all fields and more so in agriculture sector as intervention involves moving physically into insecure country side.However, this has not prevented work of CG canters including CIMMYT, and its germplasm introductions led to development and release of several wheat varieties in the country in recent past (Obaidi et al., 2011(Obaidi et al., , 2014(Obaidi et al., , 2015)).Afghanistan grows wheat at over 2.5 million hectares with an average annual production of around five million tonnes (Obaidi et al., 2015).Though adequate number of wheat varieties are available, however their dissemination to farmer fields is severely hampered on account of inefficient seed production providing for a less than five per cent seed replacement rate for wheat.The Afghan agricultural research is spearheaded by Agricultural Research Institute of Afghanistan (ARIA) which constitutes Afghanistan's national agricultural research system (NARS).ARIA has over ten functional wheat research stations spread across length and breadth of the country.Current practice of releasing new wheat varieties makes use of yield evaluation trials conducted throughout the country.Afghanistan has wide range of agro-ecologies characterized by cold winters and hot summers.Though eastern Afghanistan does receive monsoon rains, most of the Afghanistan is semi-arid or arid (Saidajan, 2012).It is therefore imperative that country is categorized into all possible wheat climatic zones to not only fine-tune production management but also identify best adapted varieties for each zone.Phenological traits mainly days to flowering is a reflection of agro climatic features of any location and can be aptly employed to characterize different agro climatic zones (Diaz et al., 2012;Pearce et al., 2016).

Material & Methods
A total of ten wheat varieties released in Afghanistan and representing different growth habits viz., winter and spring wheat were used to constitute a phenological nursery.The nursery was grown at several locations viz., Balkh, Baghlan, Bamyan, Nangarhar, Kabul, Takhar, Kunduz, Herat, Badakhshan and Kandhar during 2010-11 to 2015-16 crop seasons.Various geological attributes of these locations viz., longitude, latitude and altitude etc., are presented in Table 1 and their geographical locations are shown in Figure 1.The nursery was sown in an unreplicated experiment and each genotype was sown in two rows of two meters each.Standard recommended

Discussion
Flowering is the development stage signalling transition from vegetative to reproductive stage.Climatic factors like temperature and day length are integrated to regulate flowering time (Nitcher et al., 2014) and are thus critical parameters determining climatic homogeneity in respect of the species in question.Since optimal time of development transition is necessary for reproductive success (Diaz et al., 2012) and to maximize grain yield (Pearce et al., 2016), climatic zonation on the basis of this transition would aid identification of best adapted varieties for a zone.Though, Himani et al. (2013) reported agro climatic zonation of Uttarakhand using remote sensing and GIS, and Jatzold and Kutsch (1982) employed temperature, water supply and length of growing period for zonation of Kenya, Rezaei et al. (2016) distinguished various regions of Iran on the basis of several weather parameters.Additionally, range of weather parameters have been made use of for computing evapotranspiration (Valipour, 2015;Valipour, 2014aValipour, , 2014b)).However, it will take some time before adequate information on these aspects of Afghanistan is generated to attempt such a zonation.Moreover, we are attempting delineation of Afghan wheat acreage only with respect to a single species.Flowering time (FT) is such an adaptive trait and is the net result of interaction of environmental factors with the species concerned.Therefore, FT can be used to determine climatic homogeneity and thus create zones for the purpose of maximising species performance within the zone.The ADF varied from 95 for Nangarhar in East to a high of 161 in Badakhshan in North East.Interestingly the across location variation is echoed equally by all the genotypes studied.For example, the ADF value ranged between 155 and 169 at Badakhshan, and between 93 and 97 at Nangarhar indicating a much greater role of location in determining ADF.The wheat climatic zones proposed herein viz., East, North, South, West, North-East and Central Highlands are only a tentative working solution based on flowering stage observed among a set of wheat varieties adapted to Afghanistan.However, owing to similar ADF and lack of adequate number of testing sites South-West will be only one zone for the time being.Similarly, North-East is clubbed with Central highlands for same reasons.Wart et al. (2013) suggested an effective balance between zone size and number of zones required to adequately cover the harvested area of major food crop.Afghanistan on the other hand suffers from lack of adequate number of regional research stations to serve as testing sites for new varieties and is therefore constrained to manage only with the available functioning research sites.The regions especially in East, South, West and North East should have more number of research stations to better judge varietal adaptability and to optimize factors of production.The currently proposed wheat climatic zones should be changed to better delineate Afghan wheat area as and when more number of research stations are added in South, West, East and North East.

Table 2 .
region also with an ADF of 161.Though Badakhshan is not geographical contiguous region, however because of similar ADF, a zone comprising of CH and Badakhshan is proposed with the name of Highlands.Average number of days to 50% of flowering of different varieties at several locations over2010-11 to  2015-16

Table 3 .
Regions falling under different categories based on average number of days to 50% flowering (ADF)