Maize is highest yielding crop among cereals. It is growing on 4.8% of total cropped area of Pakistan.
According to an estimate, it is growing on 0.9 million hectares of land and production is 1.3 million tons per annum. The demand of food is increasing day by day with increasing the population. It is the need of hour to cultivate those crops that give high yield under climate change scenario. In this perspective
The major maize producing provinces in Pakistan are NWFP and Punjab. NWFP accounts for 57% and 68% total cropped area and production respectively. Punjab is contributing in total cropped area 38% and 30% in production. Today a major issue is failure of grain formation in maize. The production is badly affected due to poor gain formation which is due to failure in pollination and some other biotic and abiotic factors.
Cause of pollination failure in maize: The main causes of pollination failure in maize are lack of viable pollen, failure of silk to emerge or non receptive silks and kernel abortion.
Lack of viable pollen: It is possible that low night temperature in early July contributes in abnormal pollen maturation due to frost injury resulting reduction in total pollen numbers and their viability. Cold snap in late May or early June can interfere in poor development of tassels. Poor pollen maturation and poor tassels initiation makes the plant more sensitive against insects and pests resulting silk clipping in maize.
Failure of silk emergence: Drought stress is a major and common factor in proper emergence of silk. The major portion of water contents is present in silk portion of corn plant so, this portion is most sensitive to the moisture stress. It slows down the elongation of the silk, late silk emergence and complete failure of silk to emerge from the ear shoot.
Silk clipping: it is observed that delayed planting corn is more susceptible to silk clipping than earlier planting corn. It is severe where non-uniform plants development occurs.
Kernel abortion: It is usually occur during early kernel developmental stage. When the activity of photosynthesis is restricted due to cloudiness, nitrogen deficiency leaves related diseases and hail damage etc. Moisture deficit and Warm nights during silks development is also contributing in the kernel abortion. In some areas, cloudiness reduced the intensity of sunlight after fertilization of the ovary which decreased the photosynthate supply to young kernels resulting kernel abortion.
Factors affecting on grain formations
Varietal Issues: It is observed that hybrid varieties are more affected than our local varieties due to less tolerance against adverse environmental conditions.
Biotic stress: Corn Root Worm and Japanese beetle attack is prominent in early planted corn. CRW feeds on the root of the corn plant and cause injury which adversely affects the productivity of corn plant.
A-biotic stress: Grain formation is affected by temperature, drought, relative humidity, wind speed, distance and angle between tassel and cob. Among all these factors fluctuations in temperature has a critical role on pollen viability. The pollen are usually sterile at above 350C. Grain filling duration reduces with risen in atmospheric temperature. If the relative humidity is low then the temperature extremes becomes more vulnerable.
Affect of uneven plant density: Plant density is a main contributor in determination of grain yield. Plant density changes the developmental pattern and architecture of plants resulting a remarkable change in carbohydrates concentration and their partition. Among all the cereals maize is most sensitive to uneven plants distribution. Many maize hybrids at low plant densities do not produce tillers effectively and often give one ear each plant.
The high population density enhances the competition for water, nutrients and space resulting poor grain set. Early sowing varieties requires high plant population for better yield than late sowing varieties. Because early hybrid are usually smaller, produce less number of leaves, low leaf area per plant and ultimately poor grain formation and low yield
Genetically improved varieties: To overcome the above mention issues, it is imperative to introduce drought and heat tolerance varieties which have a great survival potential under adverse environmental conditions. It is the need to introduce those genotypes which produce more biomass by utilizing the light efficiently by changing their canopy development.
Agronomic practices: Day and night temperature difference is contributing as a major factor in failure of pollination resulting poor gain formation and ultimately low yield. We must modify our agronomic practices to compensate the temperature difference. We should change sowing time to minimize the temperature affect.
Reducing the climate change impacts: Increase in temperature and fluctuations in precipitation are contributing a lot in poor grain formation. Industrialization, burning of fossils fuel and deforestation, methane emission from rice fields and livestock wastes are a major contributor in climate change. We must minimize these factors by tree plantation and reducing carbon emission to ensure food security for growing world population. Hence, we can increase our agricultural productivity by providing favorable conditions for grain formation.