The pace of land degradation has almost doubled across the Western Ghats of India, one of the world's ‘hotspots’ for biodiversity, owing to soil erosion, mining, and rampant urbanization. The arising nutrient depletion leading to land degradation is thus a serious threat to agricultural sustainability in this region. Delineation of spatial soil property maps for nutrient management is an effective strategy for precision agriculture. The present investigation was carried out in North Goa District in Western Ghats, a seldom researched domain in the Indian coastal region. The study involved spatial array analysis of soil properties of 383 georeferenced soil samples and used fuzzy k‐means clustering for delineation of management zones (MZs). Soils were found highly acidic with low available N, P, and medium exchangeable K with a widespread Zn, Cu, and Fe deficiency and sporadic salinity. Soil properties exhibited low to high levels of skewness except for soil pH and Mn. Correlations between soil pH and K, Zn, and Mn, between EC and Fe, between soil organic carbon (SOC) and N, P, K, Cu, and Mn was positive and significant (P = 0.01). Geostatistical analysis revealed varied distribution pattern for soil properties with Gaussian (pH, P, and Cu), spherical (EC), stable (SOC), hole effect (N), K‐Bessel (K and Fe), exponential (Zn), and circular (Mn) as best fit semivariogram models with weak and strong spatial dependence. The spatial variability was mapped, and two MZs were delineated. The developed maps will be crucial in site‐specific nutrient management for agricultural and ecological sustainability in the Western Ghats of India.

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This review on Alternaria blight caused by singly or by mixed infection is one of the most widespread and destructive disease of oilseed brassicas in all the continents. These pathogens are necrotrophs. The disease appears as black spot but later on enlarge and develops into prominent round spots with concentric rings. Many spots coalesce to form large patches showing blight and cause defoliation in severe cases. The spots on the mid-ribs of the leaves are linear and sunken. Circular to linear lesions also develop on stem and pods, which elongate at later stages. Infected pods produce small, and shrivelled seeds. This disease causes substantial yield losses as a result of several factors including reduced photosynthetic potential, early defoliation, flower bud abortion, premature ripening, siliquae dehiscence, seed shrivelling and reduced seed size, impairs seed colour and reduced oil content. This paper reviews the research on the development of Alternaria blight, describes the pathogens of Alternaria blight on rapeseed-mustard, which includes geographical distribution, economic importance, symptoms, habitat and host range, pathogen taxonomy, survival, pathogenicity and disease development, epidemiology, host resistance, breeding for disease resistance, genotypic stock, and management.

Soils of Indian Konkan region, part of ecologically sensitive Western Ghats have been subjected to anthropogenic activities of late. This has endangered the ecological security through conspicuous losses in topsoil quality. The rationale of the present study was to map the soil properties and create management zones for ensuring food and nutritional security. The study was conducted in South Goa district of the state of Goa located in Konkan region. A total of 258 geo-referenced soil samples were collected and analyzed for pH, EC, SOC, available N, P, K and DTPA extractable micronutrients viz., Zn, Cu, Fe and Mn. Soil pH was found to be in acidic range. A wide variability existed in SOC content ranging from 0.12–5.85%. EC was mostly neutral with mean value 0.08±0.37 dSm-1, while available nitrogen (AN), available phosphorus (AP) and available potassium (AK) varied in range from 56.4–621.6 kg ha-1, 0.5–49.7 kg ha-1 and 31.5–786.2 kg ha-1 with mean values 211.2±76.9, 8.4±8.2 and 202.3±137.6 kg ha-1, respectively. A wide range was exhibited by cationic DTPA extractable Zn, Cu, Fe and Mn with mean values, 0.22±0.30, 0.44±0.60, 7.78±5.98 and 7.86±5.86 mg kg-1, respectively. Soil pH exhibited significant positive correlation with EC, AP AK and Zn and negative correlation with Fe and Cu. SOC exhibited significantly correlated with AN, AP, AK, Zn and Fe. Geo-statistical analysis revealed J-Bessel as best fit semivariogram model for pH, AP and AK; Rational Quadratic for EC, SOC, Zn and Mn; Hole effect for AN; Stable for Cu and K-Bessel for Fe for their spatial mapping. Four principal components showed eigenvalues more than one and cumulative variability of 59.38%. Three distinct soil management zones showing significant variation in soil properties were identified and delineated for wider scale management of soils. Precision nutrient management based on spatial variation and their mapping would enable refined agricultural and environmental management practices in the region.

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