To successfully address the challenge of drought, researchers and agriculturists must first understand this complex phenomenon. That’s where agroclimatologists can help. The following are the answers to six frequently asked questions about drought to better understand the work being done by ICARDA to improve nutrition and income of the people who live in drought-prone areas.

Drought Solutions: Elimination or Adaptation

In considering the causes of drought, we first think of rainfall insufficient to sustain crop growth, or insufficient irrigation water to grow crops in areas where rainfall is normally inadequate. The picture is, in reality, more complicated than that. We need to ask the question, can we change the causes of drought, or is it something we have to live with. Unfortunately, humans have little influence on rainfall. Cloud seeding to induce rain holds little hope of making dry areas less dry. Indeed, if we are to believe climatologists and environmentalists, we are facing a future in which much of the world will have less, rather than more, rain.
One of the obvious means of mitigating drought and making up for shortfalls in rain is through irrigation, a strategy that has been used for millennia. While there have been spectacular increases in crop yields with irrigation, and there have been developments in irrigation technology in order to improve the efficiency of water use, grim reality is that water for irrigation is not likely to increase in the future. Limits in many cases have been reached. Declining groundwater levels due to over-pumping is a cause for alarm, and while surface waters, mainly rivers, have reached their capacity, agriculture will have to share a static or diminishing water supply, strained by ever-growing urban, industrial, and recreational demand.
     Thus, the only viable alternative is to cope with drought, and come to terms with the reality of a limited water supply and rising human needs. But there is hope. The more we know about drought, the better we can predict its occurrence, and better deal with its consequences. But the main source of optimism stems from the observation that some plant species are able to survive low-rainfall conditions and periods of severe drought. Plant breeders and biotechnologists have achieved considerable success in exploiting this genetic potential in developing drought resistant and tolerant crop varieties. Associated with this “war on drought,” is a more basic strategy – one that does not attract headlines – that involves maintaining optimum conditions for crop production through adequate nutrition and appropriate soil and crop management. Borrowing an analogy from medicine, the objective is to provide good nutrition to ward off diseases and ensure health and well-being.

Soil is the main source of nutrients for crop growth. Prior to the chemical fertilizer age, soil was virtually the only nutrient source, except where manures were available. Apart from nutrients, soil also provides additional physiological benefits in terms of drought, cold, and disease resistance. The soil also dictates crop quality and provides nutrients that are not needed for plant growth but nevertheless impact the end-users, i.e., humans and animals. The soil is rarely the perfect medium to meet all of the plant’s nutritional needs. Fertilization is modern science’s attempt to supplement the deficiencies of nature.

     Phosphorus (P), the second of the major elements required by plants, is widely deficient in the soils of WANA. Unlike N, use efficiency of P is low because of adverse soil reactions. Banding of P—placing the fertilizer in the soil at the base of each plant—has improved efficiency greatly, but it remains low, with 10–15 % of applied P used by the crop in any one season. While P deficiency was more severe in the past, as illustrated by field response from Pakistan with the application of superphosphate, routine fertilization has resulted in a buildup of available P in soils to the extent that responses are lower than before, and now less P fertilizer is needed in many places.
     While potassium (K) is the third major element required by crops, soils in West Asia, and in drylands

in general, are well supplied with this element, and only limited K fertilization is needed, except on sandy soils and with high K-demanding crops, such as sugarbeet and potatoes.
While little is known about other possible growth-limiting nutrients in WANA soils, such as micronutrients iron and zinc, there are indications of severe constraints in some areas. When deficiencies are identified and rectified, the impact of drought can be reduced. Another micronutrient, boron, can reduce yield when deficient, or become toxic under drought conditions.

Physiology and Water-Use Efficiency

While the soil and the added fertilizer might provide adequate nutrition for the physiological functioning and growth of plants, nutrients can confer additional indirect benefits to crops, enabling them to cope with their environment. There is evidence that K not only improves water relations in plants and thus resistance to drought, but also increases disease resistance. Boron has a similar additional effect on physiological processes. Research at ICARDA and elsewhere has shown that P fertilizer, especially when banded, has a stimulating effect on root growth, and helps the plants to exploit subsoil moisture reserves leading to better crop establishment, earlier maturity, and higher yield even in moisture-stressed environments.
    In rainfed semi-arid conditions, the goal of soil fertility and agronomic management is to optimize the efficient use of water and thus mitigate drought effects, which in WANA invariably occur at the end of the growing period in the late spring, so-called terminal drought. Fertilization, apart from increasing crop yield, also ensures higher water-use efficiency.

Agronomic Practices

Agronomy is the science of managing a growing crop in the field, and as such is complementary to the science of soil fertility and plant nutrition. Though arguably less glamorous than other areas of plant science, agronomy has contributed enormously to crop and food production worldwide. Simple, inexpensive practices have made positive impact at the farmer’s level, particularly in developing countries.
    Success of any agronomic research/technology transfer process begins with assessing improved varieties produced by breeders and matching them with management practices. Despite the vagaries of weather in the early part of the crop season (October–December), early sowing invariably produces good stand establishment and yield, regardless of the moisture stress. A key factor in agronomy has been the balancing of plants’ needs with available moisture. Thus, optimum planting densities (along with row spacing) have been established for the various crops in WANA. Similarly, as weeds compete with crops for available moisture – and thus exacerbate drought – the importance of weed control, whether chemical or mechanical, is obvious. Other practices that impact directly or indirectly on water use include legume-based rotations as a substitute for fallow and cereal monoculture and conservation tillage, as opposed to conventional tillage.

Much has been written about the role of greenhouse gases, especially carbon dioxide, in contributing to global warming and drought. Relatively little has been said, however, about agronomy’s role in providing at least a partial solution to the problem. Research at ICARDA, unique in Mediterranean-type regions, has shown that cereal rotations with legumes, such as vetch and medic, could lead to a substantial increase in soil organic matter,thus leading to the “sequestering” of carbon dioxide and its incorporation into the soil, where it benefits soil physical properties and improves soil moisture relations and soil biological conditions.

Early indications suggest that conservation tillage could also help reduce levels of atmospheric carbon dioxide. In short, good agronomic practices equate to good environmental sense.

Fundamental Contribution

Soil fertility and agronomic management are fundamental factors in the agriculture of developing and developed countries alike, and research in these fields has been instrumental in feeding the world’s growing population. Drought has been a scourge of mankind in the past and will continue to be so in the future. Science will continue to work to mitigate its effects, with due consideration to the important role played by adequate plant nutrition and sound agronomic management.

Dr John Ryan (J.Ryan@cgiar.org) is a Soil Fertility Specialist and Dr Mustafa Pala (M.Pala@cgiar.org) is a Wheat-based-Systems Agronomist at ICARDA