This was how my relatives in Ah Nang Chong prepare their vegetable beds. Once the seeds were sown, they would cut grass like lalang especially and spread them on top of the seeds in the bed . This was basically for two reasons - to prevent birds from eating the seeds, and to cool down the soil (ie. to prevent the soil from drying up under the hot tropical sun).
Hope this helps you to remember how our elders provided us with organic vegetables in those long ago days.