Site-specific management promotes the identification and management of areas within the field, which represent subfield regions with homogeneous characteristics (management zones). However, determination of subfield areas is difficult because of the complex combination of factors which could affect crop yield. One possibility to capture yield variability is the use of soil physical properties to define the management zones as they are related to plant available water. With the aim of characterizing the spatial variability of the main soil physical variables and using this information to determine potential management zones, soil samples were taken from 70 locations in a 33-ha field in Badajoz, southwestern Spain. Firstly, accurate spatial distribution maps of the soil attributes were generated by using regression kriging as the most suitable algorithm in which exhaustive secondary information on soil apparent electrical conductivity (ECa) was incorporated. ECa measurements were carried out with a Veris 3100 operating in both shallow (0–30 cm), ECs, and deep (0–90 cm), ECd, mode. Clay, coarse sand and fine sand were the soil physical properties which exhibited higher correlation with ECa (positively correlated with the finer texture component, clay, and negatively correlated with the coarser ones, coarse and fine sands), particularly with ECs. Thus, this was the secondary variable used to obtain the kriged maps. Later, principal component analysis and fuzzy cluster classification were performed to delineate management zones, resulting in two subfields to be managed separately. This number of subfields was determined using the fuzzy performance index and normalized classification entropy as the way to optimize the classification algorithm.

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Delineation of management zones using mobile measurements of soil apparent electrical conductivity and multivariate geostatistical techniques

Delineation of site specific nutrient management zones for a paddy cultivated area based on soil fertility using fuzzy clustering

Sustainable soil nutrient management with proper understanding of spatial variability of soil properties helps in enhancement of crop productivity and avoiding soil degradation. It has more importance in oil palm plantations, since the area under oil palm cultivation is on rise globally. Moreover, the crop is a nutrient-requiring one and effective nutrient management contributes about 50% of fresh fruit bunch (FFB) production. Therefore, the present study was carried out to assess spatial distribution of soil properties and to delineate soil management zones (MZs) in oil palm plantations of a hot and humid tropical region of India for efficient soil nutrient management. A total of 180 geo-referenced representative soil samples (from 0 to 0.20 m depth) were collected from oil palm plantations of Pedavegi and Denduluru mandals of west Godavari district of Andhra Pradesh, India. Collected soil samples were processed and analysed for soil properties like pH, electrical conductivity (EC), soil organic carbon (SOC), available phosphorus (P), available potassium (K), exchangeable calcium (Ca), exchangeable magnesium (Mg), available sulphur (S) and available boron (B). The values of soil properties varied widely with low (7.7%) to moderate (29.0 to 77.4%) coefficient of variations. Semivariogram analysis and ordinary kriging revealed varied spatial distribution pattern with moderate to strong spatial dependence for most of the soil properties. Development of the MZs was carried out by principal component (PC) analysis and fuzzy c-means clustering. Three PCs with eigen values >1 and accounting 60.31% of total variance were used for further analysis. On the basis of fuzzy performance index and normalized classification entropy, three MZs were identified. The MZs differed significantly with respect to studied soil properties. Thus, the study emphasized that the methodology for delineating MZs could be effectively used for site-specific soil nutrient management in oil palm plantations and other crops for maximizing crop production in the study area.

Spatial variability of soil properties and delineation of soil management zones of oil palm plantations grown in a hot and humid tropical region of southern India

Efficient, cost effective and easy to use tools are needed for site specific management of soils for increasing the crop productivity. Currently nutrient management recommendations for rice in the study are typically uniform without consideration of spatial heterogeneity of nutrient content in soil. This study has emphasized the use of management zones (MZs) as an efficient method for variable application of fertilizers. Rajnagar Block of Kendrapada District in India was selected as the study area for the present study and 225 soil samples were collected on 1.5 kilometer grids. Soil samples were analyzed for pH, electrical conductivity, soil organic carbon, available nitrogen, available phosphorous, available potassium DTPA extractable micronutrients i.e., iron, zinc, copper, and manganese. Spatial variability of these soil properties was analyzed and spatial distribution maps were generated using geostatistics and ordinary kriging technique. Further, principal component analysis and fuzzy c-means clustering algorithm were performed to delineate the management zones based on optimum clusters identified using fuzzy performance index (FPI) and normalized classification entropy (NCE). The results revealed that the optimum number of MZs for this study area was three and there was heterogeneity in soil nutrients in three MZs. The delineated MZs provide a basis of information for site-specific fertilizer management in the rice cultivated fields in the study area.

Wang Zhen-Hai <

Papers

Determination of management zones for a tobacco field based on soil fertility