Sixty five surface soil samples were collected in the flower crops grown soils of Horticultural College and Research Institute, Periyakulam, Tamil Nadu. The geo-coordinates were recorded for each sample using GPS. Field maps were digitized for its field number-wise boundary and other features. Soil samples were collected, processed and anlaysed for soil physico-chemical and soil fertility properties. Analytical results of flower-grown soil samples indicated that samples were acidic to alkaline in reaction, non-saline and slightly calcareous to non-calcareous in nature. Soil fertility groupings under percent category indicated the dominance of medium organic carbon, low available nitrogen, medium to high available phosphorus, high available potassium and low available sulphur categories. In the case of available micronutrients, the dominance of low DTPA-Fe, medium DTPA-Zn, high DTPA-Mn, medium DTPA-Cu and high HWS-B were observed. The nutrient index values of the samples indicated that low status for organic carbon and available N, medium for available P and K while very low for available sulphur. Regarding to micro nutrients, the order of nutrient index values were B>Mn>Cu>Fe>Zn. Nutrient index values found to indicate for very low DTPA-Fe, Zn and Cu while marginal for DTPA-Mn and HWS-B. Thematic maps generated on the individual soil parameters clearly indicated the spatial variability of individual parameters in the flower grown soils of Eastern farm of Horticultural College and Research Institute, Periyakulam. The low fertile areas have to be improved by the conjoint application of organic and /or inorganic sources for enhanced flower production and sustainable soil fertility.
Assessment of soil properties in flower grown soils.
Nutrient Indexing of soils.
Soil fertility mapping using GIS.
Crop productivity in the semi-arid tropic region is low with an average of less than 1600 kg ha-1 (
Modern tools like Global Positioning System (GPS) and Geographic Information System (GIS) are highly useful in generating spatial variability maps of nutrients (
Sixty five surface soil samples were collected from the fields of Eastern Farm of Horticultural College and Research Institute, Periyakulam, Tamil Nadu. The geo-coordinates were recorded for each sample using GPS (
Collected soil samples were air-dried, sieved through a 2 mm sieve, labeled, and stored for analysis. Soil samples were sieved with a 0.5 mm sieve for the estimation of organic carbon. The soil samples were analyzed with standard procedures. Soil pH and EC were estimated as per
The analytical results of each soil sample was categorized into low, medium and high based on the critical limits as followed in Tamil Nadu (
Critical levels of nutrients for low, medium and high categories
Using the number of samples in each category, the per cent sample category and Nutrient Index Values (NIV) were calculated using the formulae furnished below.
Geocordiantes for the locations of soil sampling
Percent sample category =
Nutrient index value was calculated from the proportion of soils under low, medium and high available nutrient categories, as represented by,
Where,
The nutrient index values were rated into various categories
Database on soil analytical parameters was generated in Microsoft Excel and the thematic maps were created at the Department of Remote sensing and GIS, TNAU, Coimbatore by using Arc-GIS software. The thematic maps on physicochemical properties and available nutrient status were generated by categorizing the fertility status such as ‘Low’, ‘Medium’ and ‘High’ by showing appropriate legend for soil fertility parameters by krigging.
The overall data (65 Nos) indicated that pH of the soil varied from 5.09 to 8.33 with a mean value of 6.82. The electrical conductivity of the soil samples ranged from 0.01 to 0.21 dSm-1 with a mean value of 0.06 dSm-1 and soils were non saline. The organic carbon content of the soil samples ranged from 2.40 to 9.84 g kg-1 with a mean of 6.56 g kg-1. The free CaCO3 content in the soil samples ranged from non-calcareous to slightly calcareous in nature (3.95 to 5.65 %) with a mean value of 4.85% (
Range and mean values of various soil analytical parameters (n = 65)
The available N, P and K status of the soils varied from 165 to 322; 11.4 to 33.0 and 220 to 620 kg ha-1 with a mean of 291, 26.0 and 405 kg ha-1 respectively. The available sulphur content varied from 4.57 to 24.22 mg kg-1 with a mean of 7.26 mg kg-1 (
The DTPA extractable Fe, Zn, Mn, and Cu content ranged from 0.69 to 16.65; 0.77 to 3.59; 2.01 to 11.96; 0.84 to 2.54 mg kg-1 with a mean of 6.53, 1.29, 6.85 and 1.48 mg kg-1 respectively. The hot water soluble boron content of the soils ranged from 2.54 to 7.34 mg kg-1 with a mean of 4.91 mg kg-1.
Number of samples in each fertility category were worked out and the results are furnished in
Number samples under each category of fertility groups
Percent category samples for soil physic-chemical properties and available nutrients was worked out and the results are given in
Percent category of samples for available nutrients
Soil pH values indicated that out of total samples, 26.2 per cent were acidic, 49.2 per cent were neutral and 24.6 per cent were alkaline. All the soil samples were categorized under non saline. Among the 65 soil samples, 20.0, 70.8 and 92.3 per cent of samples are grouped under the low status for O.C, available N and S respectively. In the case of micronutrients, 44.6, 43.1 and 13.8 per cent of samples were grouped under low status for available Fe, Zn and Cu respectively.
Among the 65 soil samples, 46.2, 29.2, 30.8, 16.9 and 6.2 per cent of samples are with medium status for O.C, available N, P, K, and S respectively. Among the micronutrients, 23.1, 55.4, 29.2, and 72.3 cents of samples were classified under medium status for available Fe, Zn, Mn, and Cu respectively.
High category found to be with 33.8, 69.2, 83.1 and 1.5 per cent of samples in O.C, available P, K and S respectively. Micronutrients viz., Fe, Zn, Mn, Cu and B recorded 32.3, 1.5, 70.8, 13.8, and 100 percent of samples under high category.
Nutrient index values were worked out and the values are furnished in
Nutrient index value and fertility status
Among the major nutrients, nitrogen registered the lowest nutrient index value of 0.84 followed by phosphorus (1.75) and potassium (1.84). Among the micronutrients, the order of nutrient index values was B>Mn>Cu>Fe>Zn. Nutrient index values for organic carbon and available N were low while for available P and K, the nutrient index values were medium. Nutrient index values for available sulphur found to be very low. With respect to micronutrients, DTPA-Fe, Zn and Cu were classified under very low while DTPA-Mn and HWS-B were marginal. Similar results were reported by
Spatial variability maps for soil pH, O.C, available-P, S and Fe
Thematic maps were generated for soil pH, EC, organic carbon and available nutrient status by showing appropriate legend for the respective parameters (
Soils of flower-grown soils of Eastern farm of Horticultural College and Research Institute, Periyakulam were acidic to alkaline in reaction, non saline and slightly calcareous to non calcareous in nature. Soil fertility groupings with per cent sample in each category revealed the dominance of medium in organic carbon, low in available nitrogen, medium to high in available phosphorus, high in available potassium and low in available sulphur. With respect to soil available micronutrients, dominance of low category in DTPA-Fe, medium in DTPA-Zn, high in DTPA-Mn, medium in DTPACu and high in HWS-B were observed. GIS found to be an essential tool in converting the numerical values of soil parameters into visual images for better understanding of soil properties, soil constraints and to generate site specific management strategies for sustaining soil fertility. Application of organic manures, green or green leaf manures or any other natural organic sources is essential for improving the productivity of soil. Identified deficient nutrients in soils have to be reinstated through chemical fertilizers and/or natural means. Soil test based fertilizer recommendations along with micronutrients is advocated for enhanced crop production and sustained soil fertility.