MAIZE being the highest yielding cereal crop in the world is of significant importance for countries like Pakistan where rapidly increasing population has already out stripped the available food supplies. In our country, maize is the third important cereal after wheat and rice. It accounts for 4.8 per cent of the total cropped area and 3.5 per cent of the value of agricultural output. It is planted on an estimated area of 0.9 million hectare with an annual production of 1.3 million tonnes. The bulk of the production (97 per cent) comes from NWFP, accounting for 57 per cent of the total area and 68 per cent of total production. Punjab contributes 38 per cent acreage with 30 per cent of total grain production. Very little maize --2-3 per cent -- is produced in Sindh and Balochistan.

Though not included in Pakistan’s official statistics, maize is an important crop of Azad Jammu and Kashmir. It is planted over about 0.122 million hectare in AJK during kharif. Similarly, a very high yielding sector of maize, the spring maize area and production in Punjab is not accounted for in the statistics which covers around 0.070 million ha with about 050 million tonnes of the grain being produced.

It is grown almost all over Pakistan under varied soil and climatic conditions. It grows best on fertile, well-drained loamy soils. Management of inputs particularly irrigation water using modern technology is essential for maximising production and for providing high return to farmers. The most critical period of maize growth, during which water stress affects yield, is between two weeks before and 2–3 weeks after silking. Proper scheduling of irrigation to apply required quantities of water during the critical period, yet allowing moderate stress at vegetative and maturity stages is necessary for good growth and yield.

Rising cost of irrigation pumping, low commodity prices, inadequate irrigation system capacities and limited irrigation water supplies are among the reasons that prompt many irrigators to deliberately apply less water than is required to obtain maximum yield. The goal of effective management of irrigation water is to enhance economic returns with limited use of water and/or energy. Regulated deficit irrigation provides a means of reducing water consumption while minimising adverse effects on yield. By deficit irrigation, crops are deliberately under-irrigated during plant growth stages that are relatively insensitive to water stress. Identifying growth stages of a particular cultivar under local conditions of climate and soil fertility allows irrigation scheduling to maximise crop yield and most efficient use of scarce water resources, Therefore, irrigating a crop with required quantity of water during the moisture sensitive period of flowering and yield formation stages, yet allowing moderate stress at vegetative and maturity stages produce the optimum yield with maximum water use efficiency and water economy in most of the crops yields on marginal lands would reduce.

Fresh water is becoming scarce not only in arid and drought prone areas but also in regions where rainfall is abundant. Effective management of water for agricultural production in water scarcity regions therefore requires the use of innovative and sustainable approaches. Under normal condition the maize crop yield may be affected up to 10-13 per cent but during the severe years of drought the loss may increase many folds. The problem is more severe under barani conditions covering an area of 25-30 per cent of major crop planted in the country.

Planting date is a particularly important consideration for maize production in drier areas. When maize is planted under appropriate soil moisture and temperature conditions, the chances of complete germination and crop establishment increase greatly. Where the length of the growing season is limited by the duration of the rainy season, early planting reduces the probability of drought during the late grain–filling stage. Delayed planting exacerbates agronomic problems, often resulting in a crop that is tall, prone to lodging, and with relatively fewer kernels per plant. These effects, together with the increased possibility of terminal drought stress, can result in significant yield losses.

By reducing runoff or diverting runoff from other areas onto a plot, water harvesting can also contribute to increased crop yields in the semiarid tropics; however, water harvesting in maize, which is susceptible to water-logging, can provide too much water to the crop in some seasons.

In semi-arid areas, as much as 50 per cent of total evapo-transpiration from a crop can be lost through evaporation from the soil surface. Losses are highest during early crop growth. Mulch can play an important role in reducing soil evaporation and temperature. Crop residue mulches have been shown to increase maize yields significantly in semiarid at application rates as low as two t ha-1, and they have been closely associated with increased water capture compared with conventionally tilled plots. In a series of on-farm trials conducted in a semiarid tillage, chemical weed control, and mulch applied at two t ha-1 increased water capture by 65 per cent compared with a treatment that comprised two disking and mechanical weed control. The result was an increase in grain yield of up to 100 per cent.