MAJOR PLANT NUTRIENT LEVELS IN SOME WELLS ALONG A SOFT CATENA UNDER INTENSIVE VEGETABLE CULTIVATION

Abstract

Well water could be loaded with plant nutrients by over applications of fertilisersand manure. This could be perilous to the environment. Over applications offertilisers and manure are very common in hill-country vegetable croppingsystems of Sri Lanka.

In this study, major plant nutrient levels in 7 wells along a soil catena in Pattipolaunder intensive vegetable cultivation were monitored. A well in the forest ofupper catena was selected in the control.

Water was sampled in weekly intervals for 3 months. pH of those was measuredin -situ, K, Ca, Mg, P04, P, NH4-N and NOrN were determined in preservedsamples. A quantification of the nutrients recycled through irrigation issues wasalso done.

pH-values of water in the cultivated segments were in moderately acidic range of4.4 - 4.9 compared to 5.2 of the control. Ca, P04-P and NH4-N levels were low inpar with the correct due to the considerable adsorption by the soil.

However, K, Mg and NOrN levels were contrastingly higher that that of thecontrol indicating the influence of fertiliser and manure applied. Some wells ofthe lower slope showed> 28 ppm NOrN compared to 2 ppm of the control.

4, 9, 1.5, 2 and 20 kg/ha of Ca, Mg, P04-P and N were brought back to cropsthrough an average irrigation issue showing a mild similarity to a foliar fertiliserapplications.