Nitrogen replenishment using variable rate application technique in a small hand-harvested pear orchard

Anna Vatsanidou,Theofanis A Gemtos,Spyros Fountas,Anamaria Castrignano,John Baras,George D Nanos

doi:10.5424/sjar/2017154-10986

Abstract

Precision agriculture is a management approach for sustainable agriculture. It can be applied even in small fields. It aims to optimize inputs, improve profits, and reduce adverse environmental impacts. In this study, a series of measurements were conducted over three growing seasons to assess variability in a 0.55 ha pear orchard located in central Greece. Soil ECa was measured using EM38 sensor, while soil samples were taken from a grid 17 × 8 m and analysed for texture, pH, P, K, Mg, CaCO3, and organic matter content. Data analysis indicated that most of the nutrients were at sufficient levels. Soil and yield maps showed considerable variability while fruit quality presented small variations across the orchard. Yield fluctuations were observed, possibly due to climatic conditions. Prescription maps were developed for nitrogen variable rate application (VRA) for two years based on the replacement of the nutrients removed by the crop. VRA application resulted in 56% and 50% reduction of N fertiliser compared to uniform application.

Highlights

Site-specific crop management (SSCM) within management zones aims to match resource application and agronomic practices to soil and crop requirements (Whelan & McBratney, 2001)
A series of measurements were conducted over three growing seasons to assess variability in a 0.55 ha pear orchard located in central Greece
Prescription maps were developed for nitrogen variable rate application (VRA) for two years based on the replacement of the nutrients removed by the crop

Summary

Introduction

Site-specific crop management (SSCM) within management zones aims to match resource application and agronomic practices to soil and crop requirements (Whelan & McBratney, 2001). Two methods of implementing SSCM for variable rate application (VRA) of crop inputs are used: sensor-based and map-based management zones (Zhang et al, 2002). Developing management zones and prescription and application maps, based on historical data, can be the basis for variable rate inputs applications. A N prescription map based on nutrient removal by the fruit was created for an apple orchard by Aggelopoulou et al (2011). They claimed that if N was applied site-38% of N could be saved compared to uniform application. In a similar study Zaman et al (2005) found that N-VRA resulted in a 40% cost reduction for fertilisation in citrus orchards

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