Seed Health Management for Better Productivity - Govind Ballabh ...

(Seed Health Management for Better Productivity)3. Isolation: The seed production plot must be isolated from various sources of contamination bya certain minimum distance known as isolation distance. Isolation is more important in crosspollinatedcrops to avoid genetic contamination through cross-pollination whereas in a strictlyself pollinated crop, it is mainly to avoid mechanical mixture from adjoining fields. Isolationrequirement varies from 3 metres in self pollinated crops like wheat and paddy to hundreds ofmetres in cross-pollinated crops (1600m in case of cabbage, cauliflower etc.).4. Seed rate/row spacing: Planting density may influence quality of produce due to completionbetween plants for resources like nutrients, water, light etc. Limited literature available does notindicate significant differences in seed quality probably because of compensatory mechanismof crop plants.5. Method of sowing: The seed crop must be sown in lines. It should be sown in such a way thatit facilitates movement of personnel for effective roguing. This can be achieved by skipping arerow after every eight to ten row in wheat seed crop. Paired row planting can be adapted incase of paddy, green gram and chickpea. The seed drill (cups, pipes and box) must be cleanedbefore and after sowing of one variety.In hybrid seed production, male and female parents must be planted in the recommendedratio. The row direction is very important in wind pollinated crops and it should be kept nearlyperpendicular to the prevalent wind direction at the time of flowering.6. Mineral nutrition: Application of nutrients especially in soils which are deficient in one or moreelements may affect seed quality parameters. Nitrogen application increases seed protein contentwhich influences seed quality probably by influencing enzymes as all enzymes are proteins. Loweand Ries (1973) found an increase in seed protein content with increase in nitrogen application.More than 86% of seed protein was found in endosperm of wheat seed. Nandisha andMahadevappan (1984) found increase in seed vigour parameters with increases in NPK level andattributed it to increase in seed size and seed protein content.7. Irrigation: Irrigation is related to supply of soil moisture. Soil moisture stress at critical growthstages will adversely affect the seed set and seed filling. For most of the crops flowering is mostcritical stage. Withdrawal of irrigation during flower bud initiation stage will adversely affect thenumber of seeds to be formed. Similarly, moisture stress during grain filling stage will reduce seedsize which will have low vigour. In case of rice, panicle emergence has been found to be mostcritical stage. If drought occurs at this stage, whole inflorescence will become sterile.8. Weed management: Weed control is an important aspect of seed production. Weeds present incrop not only compete with crop plants for resources but also affect seed quality by reducing thesize of seeds and yield. Presence of weed seeds especially those which are inseparable from cropseed may lead to rejection of the seed lot. The seed lot must meet minimum seed certificationstandards. The total number of weed seeds present in the field/seed sample should not exceed thelimit which is zero in some cases. Similar is the case with diseased seeds. Therefore, due careshould be taken for control of diseases especially those in which seed is carrier of pathogen.- 68 -