MSc

A major constraint in the production of vegetables in the humid tropics is heavy infestation of weeds. The extent of damage due to weeds varies with the crop and the nature of weeds. Okra [Abelmoschus esculentus (L.) Moench.] is an important vegetable crop grown throughout India in summer and rainy seasons. Being a widely spaced crop, weeds are always a problem for the successful cultivation of okra. Because of the high cost and drudgery involved, traditional methods especially hand weeding is on the decline. Chemical weed control is a cost effective option to manage this situation. However, depending only on chemicals is not advisable considering the ill effects due to continued use of chemicals.

Mulching, a non chemical method of covering the land surface with organic or inorganic materials is commonly followed in many crops especially vegetables for managing weeds, conserving moisture and for many other benefits.

The present experiment entitled “Efficacy of mulches for weed management in okra [Abelmoschus esculentus (L.) Moench.]” was conducted in the Department of Agronomy, College of Horticulture, Vellanikkara in the summer season of 2014 to compare the efficiency of different organic mulches for managing weeds of okra and to assess the effect of mulching on soil-plant micro site variations. Treatments included mulching with five organic mulches (mango leaves, coconut fronds, fresh weeds, paddy straw and newspaper), mulching with black polythene sheet, weed management by herbicide, hand weeding and unweeded control.

Mulching with black polythene sheet greatly increased the plant height, while organic mulches did not show any significant effect. Organic mulches of newspaper, mango leaves and paddy straw facilitated higher uptake of nutrients by crops. Mulching with black polythene sheet, paddy straw and mango leaves favoured earliness in flowering. The number of fruits per plant was higher in plots mulched with black polythene sheet followed by hand weeding. Black polythene sheet mulching recorded highest fruit yield of 15.63 t/ha followed by hand weeding (12.02 t/ha). Among organic mulches, mango leaves recorded 10.06 t/ha yield which was higher than the yield in herbicide sprayed plot (9.56 t/ha). Mulching with newspaper resulted in a yield of 9.37 t/ ha.

Mulching with paddy straw, mango leaves and newspaper resulted in 70 to 95 percent control of weeds at 30 DAS. The efficiency of organic mulches reduced to 30 to 50 percent at 60 and 90 DAS. Mulching with fresh weeds and coconut fronds failed to check weed emergence. Black polythene sheet was superior among the mulches throughout the crop period. Weed index of the treatments mulched with mango leaves and newspaper were found almost similar to that of pre emergent spray of pendimethalin. Nutrient removal by weeds was lower under organic mulches of newspaper and mango leaves.

An increase in the soil pH was observed towards the harvest of the crop. The soil organic carbon content was also found to be increased due to use of organic mulches. Higher contents of available N and K were observed in mulched plots compared to bare soils of hand weeded and herbicide sprayed plots. However, available P status was not influenced by treatments.

Organic mulches helped to reduce the soil temperature throughout the crop growth period. Higher moisture content was noticed in mulched plots compared to bare soil. Among them, paddy straw and coconut fronds exhibited greater influence. There was no significant difference in relative humidity at canopy level due to mulching. The treatments greatly influenced the population of bacteria, fungi and actinomycetes. In general, organic mulches, especially paddy straw favoured microbial population.

The highest benefit-cost ratio of 2.77 was recorded in black polythene sheet mulching. The B:C ratio of mango leaf mulching and pre emergent spray of pendimethalin were almost same (2.73 and 2.72 respectively). Mulching with newspaper resulted in a B: C ratio of 2.49. From the experiment, it can be concluded that organic mulches of mango leaves and newspaper can be effectively utilized for weed management in okra. The results also suggest the possibility of replacing herbicides with organic mulches without affecting yield or benefit-cost ratio.