There are many reasons, most notable are:
1. Soil moisture limitations and poor ground water level
2. Poor organic matter and microbial population
3. High temperature and wind velocity
4. High diurnal variation
5. Difficult to conserve moisture and reduce evapo-transpiration
6. Lack of irrigation facilities and little scope to improve it
7. Poor soil nutrient status
8. Poor availability of residues
9. Little scope for multi-crop cultivation and aggregate stability
10. Very difficult to change mindset of local farmers
Dr. Tarafdar has summarised the reasons for why different kinds of technological packages are required for crop cultivation . Most important technology which we requires for dry land crop cultivation is short duration varieties of all the crops grown in different rain - fed situations. Early maturing short duration crop varieties can solve 50% of the problems . More over system diversification by using different agroforestry technologies can solve rest 50% problems of rain-fed agriculture.We can not bring even a of fraction dry lands under irrigation , in this situation appropriate location specific agroforestry technologies are only alternative.Regards.
In dry-land crop production, we are dealing with water limitations which affect the plant physiology across a dynamic season. So the soil water availability AND the aerial environment are often variable across the season and between seasons. There are many interactions; for example what happens early in the season can interact with the genetics (early and later maturity, and plant population and inter and intra row configuration (crop management). There are biomass and leaf area development variation, and the particular soil water availability which affect the actual use of water. Root systems may be shallow or grow and can gradually extract water from depth (sorghum can extract from down to 2 meters) . Finally high temperatures affect the crop development (phenology) ( Think time and temperature as degree days,) and the high temperature stress can also affect grain sterility and grain fill, and hence yield
By contrast irrigated crops are often under optimum or more optimum conditions than dryland and tailored water management can avoid some of the drought effects. The micro-climate around the plant can ameliorate some of the severe effects of high temperature. However one benefit of a drier atmosphere can be the reduced diseases (fungal pathogens like humidity).
Interestingly the pearl millet can grow as a hill planted crop, ( hill planting = several plant is a hole and widely spaced in dryland situations) and the large number of tillers can provide a slight improvement in the localised microclimate around the plants.
Let me add my bit also , since question is so tempting to be responded. We surely need a different strategy for dryland vis-a-vis irriagted land , simply because of entirely different dynamics of water, nutrients, insectpests and diseases, in addition to difference in productivity level . Likewise , we also need to differentiate dryland areas of hill versus plain land , from technology development point of view...
Technology per se will remain the same, but the issues, potentials, problems and solutions and applicability pertaining to dry land agriculture will be specific and totally different from that of general/irrigated agriculture
Each environment has a different carrying capacity for each agricultural commodity. Such carrying capacity as mentioned above. Therefore, the method of cultivation must be different.
I am also of the opinion that each production zone/climatic zone to be treated differently owing to their potentials and limitations, taking into consideration those technologies, which have more applicability in those zones. Sharpening of the technology available also help after doing extensive adaptive research trials and front line demonstrations
There is one basic difference between irrigated farming and dryland farming is assured water availability ( irrigation) and unassured water availability through rainfall only( drylands). Now there are three possibility for drylands 1. Harvest rainwater and use it efficiently 2. No rainwater harvesting but risk minimisation with multi-component system (annual+ perennial +animal/fish/bird/economic fauna) 3. Integration of both 1 and 2. This can be basic approach.
However , since the advent of green revolution that was basically made for irrigated areas , the whole technological package of green revolution has been trying to introduce in drylands,one or the other way by scientist or extension functionaries as they taught during their education that without intensive monocropping + use of fertilizers+ pesticide+ hybrids, yield increase is very difficult and same they apply in drylands that caused a devastating effect -as we all see cotton growing rainfed areas of central India. If this heavily invested crop is failed there is no option to survive. Otherwise farmer can easily sustain their life as we can still see in the multi- component default organic areas of northwestern India. In drylands the major issue is sustainability rather than productivity or profitability. Efficient use of local resources contributes more to sustainability than the use of external inputs in drylands. This need to be imbibed in the mental setup of scientists and extension workers. Even the ground water irrigated areas need to adopt this approach as later or sooner they become part of drylands due to meager efforts for ground water recharge.
The second aspect is to respect/restore/revisit the time tested traditional wisdom/knowledge that has taken centuries for refinement and reached to present status. These technologies have been continuously tested in all the climatic variations that is impossible to test by a scientist in his 10-15 year service at one place and era of fast changing targets and achievements . This is rich wealth of knowledge that is fortunately available with most of the old civilisations.
Third aspect is -unlike irrigated areas ,in drylands not even two farmers is having same set of socio-economical and agro-ecological conditions, therefore , a single technology cannot be recommended even for one village and every farmer need to be empowered with customized information according to his conditions.
The forth aspect is technology need to be simple , locally available and adoptable in low investment so that it can be reached to the majority of resource poor farmers of drylands. Please see one such model at http://www.cazri.res.in/publications/AKSharma1.pdf
With incorporation of some high value crops like spices in production system and local value addition can add to income of drylands farmers to a great extent.
We have succeeded in input management particularly fertilizer, only under irrigated conditions. Our irrigated area technology fails many times under dryland farming. We need to generate technology under moisture stress conditions in the near future to sustain crop production, and in this direction drought tolerant/resistant varieties of crops and their PoPs need to the major research agenda of our institutions. Once this becomes the major research agenda, definitely new technologies will start pouring in with in a short spell of years.
Many times we talk about the technology for water storage under dryland agriculture. This is known to us for over 2-3 decades. Again this facilitates, limited irrigation agriculture, where water-nutrient interaction shows the success. Why don't we think of crops varieties which can withstand extreme drought! I may think the extreme example of Opuntia spp. If there is any breakthrough in transferring genes for drought tolerance from this species to our cultivated varieties, this may do wonders. I am optimistic. The day may come!
Not only genetical screening of varieties, there are some micronutrient elements like chlorine, which can impart drought resistance to some extent in coconut palm and chlorine in coconut palms of coastal areas is the most absorbed ion after potassium ions
Thank you very much. Perhaps more integrated planning is required for rainfed drylands as cultivation is done under uncertainties, unlike irrigated conditions where systems are under controlled to maximum extent.
EXPERIENCE OF DRY FARMING IS A MUST IN THESE SYSTEMS
I do agree we should also grow drought tolerant crops and even use species that are not in the top ten. Tepary bean is a bean under drought . Millet and sorghum are useful . Unfortunately it is even harder to get resources to work on some crops compared to the big five supported by seed companies. There is an appetite for novel and super foods- which may assist in the funding of the less grown species.
We have to gather more information on sodicity (of surface as well as sub-soil), acidity (of surface as well as sub-soil), salinity (of surface as well as sub-soil) and calcareousness (of surface as well as sub-soil), Fe/Al toxicity tolerant crop species/variety apart from hot/cold/dry/submergence tolerant ones to counter this and other related issues
There is merit in they being separate. One involves using natural (rainwater) and the other involves using water stored in a reservoir or ground. There can be differences in the way water is applied to soil, transmitted through it and its interaction with salts in soil and their movement. However, the technology developed in both should aim at improved crop water productivity with least bad effect on soil.
Thank you very much for response. Besides water, ecosystem features like slope etc are important for technology implementation
Minimum or no tillage mulching and return of crop residues also be in place to reduce water and nutrient losses and conservation
thanks for message.
Some times in rainfed drylands minimum tillage is resulting in problem of surface crusting also
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