Effects of fertigation on sugarcane yield, agronomic traits and soil fertility in sugarcane fields

TO SYSTEMATICALLY QUANTIFY THE EFFECTS OF FERTIGATION ON SUGARCANE YIELD FORMATION AND SOIL FERTILITY AND TO IDENTIFY THE OPTIMAL DRIP-FERTIGATION REGIME FOR SUGARCANE GROWN ON TYPICAL RED-SOIL SLOPING LAND IN SOUTHERN CHINA, THREE CONTROLS (CK₀, RAIN-FED; CK₁, CONVENTIONAL BROADCASTING; CK₂, BROADCASTING + DRIP IRRIGATION) AND 9 FERTIGATION TREATMENTS WERE ESTABLISHED. THE TREATMENTS COMBINED 3 IRRIGATION RATES I₅₀ (800 M³·HM^-2), I₇₅ (1200 M³·HM^-2), I₁₀₀ (1800 M³·HM^-2) WITH 3 FERTILIZATION RATES: F₅₀ (180 kg·hm^-2 N + 90 kg·hm^-2 P₂O₅ + 60 kg·hm^-2 K₂O kg·hm^-2), F₇₅ (270 kg·hm^-2 N + 135 kg·hm^-2 P₂O₅ + 90 kg·hm^-2 K₂O HA⁻¹), F₁₀₀ (360 kg·hm^-2 N + 180 kg·hm^-2 P₂O₅ + 120 kg·hm^-2 K₂O kg·hm^-2). SUGARCANE YIELD, AGRONOMIC TRAITS, AND TOPSOIL AND RHIZOSPHERE SOIL FERTILITY WERE DETERMINED. COMPARED WITH CONVENTIONAL BROADCASTING AT THE SAME FERTILISATION RATE, FERTIGATION AT F₁₀₀ SIGNIFICANTLY INCREASED CANE YIELD, SINGLE-STEM WEIGHT AND PLANT HEIGHT BY 11.32%~11.55 %, 6.22%~15.91 % AND 5.23%~6.93 %, RESPECTIVELY, AND MARKEDLY RAISED TOPSOIL AND RHIZOSPHERE CONTENTS OF AVAILABLE P, AVAILABLE K, TOTAL ORGANIC CARBON, LABILE ORGANIC CARBON AND MINERAL-ASSOCIATED ORGANIC CARBON. YIELD, AGRONOMIC CHARACTERS, SOIL NUTRIENT CONCENTRATIONS, ENZYME ACTIVITIES, ORGANIC CARBON FRACTIONS AND THE CARBON MANAGEMENT INDEX ALL ROSE WITH INCREASING FERTILISATION. GREY-WEIGHTED RELATIONAL ANALYSIS SHOWED THAT FERTILIZATION RATE WAS THE PRINCIPAL FACTOR GOVERNING INTEGRATED SOIL FERTILITY, WHEREAS IRRIGATION RATE HAD NO SIGNIFICANT EFFECT; THE I₇₅F₁₀₀ TREATMENT PERFORMED BEST. PRINCIPAL-COMPONENT REGRESSION REVEALED THAT LABILE ORGANIC CARBON, MINERAL N AND AVAILABLE P IN THE TOPSOIL, TOTAL ORGANIC CARBON, MINERAL-ASSOCIATED ORGANIC CARBON AND PARTICULATE ORGANIC CARBON IN THE RHIZOSPHERE, AND PLANT HEIGHT AND STALK NUMBER WERE THE DOMINANT DRIVERS OF CANE YIELD. THESE INDICATORS SHOULD RECEIVE PRIORITY ATTENTION WHEN DESIGNING DRIP-FERTIGATION STRATEGIES FOR SUGARCANE PRODUCTION.