PhD

The response of common rainfed intercrops of coconut to varying levels of shade and its nutrient requirement as intercrops in coconut garden were evaluated by conducting two field investigations at College of Agriculture, Vellayani during 2001 – 2002 and 2002 – 2003.
The first investigation entitled “Screening of crops under varying intensities of shade” was laid out in RBD with four treatments and five replications. The treatments included were 0, 25, 50 and 75 per cent shade. Shade significantly influenced all growth and yield parameters of the crops under study.
Among the fourteen crops cassava, sword bean, upland rice and sesamum were classified as ‘shade sensitive’ on the basis of their performance and yield under different shade levels. These crops showed significant increase in height of the plant and chlorophyll content under shaded situation but the parameters like LAI, DMP, NAR, CGR, RGR, LAD, SLW, stomatal index, root volume, root-shoot ratio, leaf proline content and nutrient uptake were decreased markedly with increasing shade intensity.
The yield and yield contributing characters of all these crops declined drastically even under low shade intensity. Hence these crops were included in the group of ‘shade sensitive’ crops.
The crops like chittaratha and stylo were classified as ‘shade tolerant’ based on their yield performance. The height of plant and chlorophyll content increased under shade, whereas the number of leaves, LAD, DMP, SLW, stomatal index, root volume, root-shoot ratio, leaf proline content and uptake of nutrients were decreased for both the crops. NAR, CGR, RGR and LAD were worked out only for chittaratha and all these parameters except RGR showed a reduction under shade which was maintained at 3.19 mg g-1 day-1 up to 25 per cent shade during later stages of growth.
The yield and yield contributing characters showed a decline with increase in shade intensity for both chittaratha and stylo. The reduction in yield was almost proportionate to the increase in shade intensity. Hence these crops were included in the group of ‘shade tolerant’ crops.
Chilli, tomato and ragi were classified as ‘shade intolerant’. The plant height and chlorophyll content of these crops increased under shade, while parameters like number of leaves, LAI, DMP, NAR, CGR, RGR, LAD, SLW, stomatal index, root volume, root-shoot ratio, leaf proline content and nutrient uptake were decreased. But tomato showed an exception with a significant increase in NAR, CGR and RGR up to 50 per cent shade in early stages and a decline in the later phase.
The yield and yield contributing characters decreased with increase in shade intensity for chilli, tomato and ragi. Even though the reduction in yield was significant it was not proportionate to the increase in the intensity of shade. Hence these crops are classified as ‘shade intolerant’ crops.
The crops viz., arrowroot, kacholam, patchouli, pineapple and thippali were classified as ‘shade loving’. The height of plant, number of leaves, LAI, DMP, LAD, root volume, root-shoot ratio, chlorophyll content and uptake of nutrients increased under shade for all these crops. Parameters like NAR, CGR, RGR and stomatal index decreased with increase in shade for arrowroot, kacholam and thippali. SLW of kacholam, patchouli and arrowroot were increased under shade, while that of thippali increased only during early stages and decreased during later stages.
The yield and yield contributing characters of all these crops increased under shade. These crops produced higher yield under shade compared to open, eventhough the response varied under different shade intensities. Hence arrowroot, kacholam, patchouli, pineapple and thippali are classified as ‘shade loving’.
The climatic parameters like canopy temperature, can evaporation and soil temperature were highest under open, whereas soil moisture content increased significantly with increasing shade intensities.
The absolute weed density as well as weed dry matter of grasses and sedges was highest under open, whereas both these parameters for broad-leaved weeds increased upto 50 per cent shade.
The second investigation “Field verification trial for nutrient management” was taken up after completion of the screening trial. One crop was selected from each group viz., shade sensitive, shade tolerant, shade intolerant and shade loving for this experiment. The crops selected were ginger (shade loving), colocasia (shade tolerant), tomato (shade intolerant) and cassava (shade sensitive). It was laid out in RBD with five treatments and four replications in coconut garden with 50 per cent shade. The treatments were fixed based on nutrient uptake as observed from previous experiment corrected to the soil test values taken as T1, T2 – 50 per cent higher level of correction, T3 – 50 per cent lower level of correction, T4 – POP for the crop tested and T5 control (without fertilizers).
The different fertilizer levels did not have any significant influence on plant height, number of tillers and DMP of ginger. All other observations including fresh and dry ginger yield varied appreciably due to the nutrient levels. The treatment receiving nutrients at 50 per cent above correction recorded significantly higher values for number of leaves, fresh and dry ginger yield, harvest index, uptake of nitrogen, phosphorus and potassium, BCR and net returns. This treatment was significantly superior to all other levels including POP recommendation for fresh and dry ginger yield and economic parameters. Hence for ginger the nutrients applied at 50 per cent above correction can be recommended as the most suited treatment under 50 per cent shade level.
The growth characters like plant height, number of tillers, number of leaves and nutrient uptake of colocasia were significantly influenced by the different fertilizer levels recording maximum values at 50 per cent above correction. The tuber yield and DMP of colocasia were highest at this nutrient level and on par with POP recommendation and correction level.
The harvest index, BCR and net returns were significantly superior at 50 per cent above correction. Hence for colocasia this level of nutrients could be recommended for similar conditions.
In cassava, the plant height, number of leaves and uptake of nitrogen phosphorus and potassium were highest at 50 per cent above correction. The tuber yield, DMP, BCR and net returns were also significantly superior at this treatment. Hence 50 per cent above correction could be recommended as the most suited treatment for cassava when grown under coconut gardens with 50 per cent shade level.
The different fertilizer treatment significantly influenced the plant height, number of branches, number of leaves, yield, uptake of nutrients, BCR and net returns of tomato recording maximum values at 50 per cent above correction.