Legume Cover Crop Effects on Temperate Sugarcane Yields and Their Decomposition in Soil

Paul M White,Howard P Viator,Gregory Williams,Charles L Webber,Ryan P Viator

doi:10.3390/agronomy10050703

Paul M White, Howard P Viator + Show 3 more

Open Access

https://doi.org/10.3390/agronomy10050703

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Abstract

Sugarcane is commercially produced on 340,000 ha in the US and is valued at over $1 billion US annually. Cultural practices that improve sugarcane sustainability are needed to maintain yields in fields with degraded soils. Historically, leguminous rotation crops provided organic matter and biologically fixed nitrogen (N) for subsequent sugarcane crops. Currently, sugarcane is usually grown as a monoculture with only a short, 6-month fallow period. The objective of these field studies was to determine how growing cowpea (Vigna unguiculata (L.) Walp.) and sunn hemp (Crotalaria juncea L.) as cover crops during fallow affected the yield of subsequent sugarcane crops. A companion laboratory study investigated the decomposition rate of cover crops in soil at different temperatures. Cowpea and sunn hemp production produced 12.8 t/ha dry matter and 250 kg N/ha. Cowpea generally improved plant cane yields, but the effects of sunn hemp varied. However, neither cowpea nor sunn hemp reduced cane or sucrose yields consistently, and mineral N additions may have a role in mitigating yield gains or losses. Based on laboratory data, the average half-life for cowpea and sunn hemp would be 3 months. Overall, using legume cover crops should be viewed as an important component of sustainable sugarcane practices.

Highlights

Cultural practices that improve the sustainable production of regionally specific crops are needed to ensure the economic viability of rural areas and to protect natural resources
The cultivation of soybean in rotation with sugarcane for use as a hay and/or green manure was a standard practice in Louisiana nearly a century ago, partially to take advantage of the N fixed by legume [3]
Data indicated sucrose yield of up to 7% higher by average, over nine sugarcane crops, by growing soybeans, which were incorporated as a green manure, compared to soybean that was removed for hay

Summary

Introduction

Cultural practices that improve the sustainable production of regionally specific crops are needed to ensure the economic viability of rural areas and to protect natural resources. In Louisiana, the perennial crop is usually grown on a five-year cycle that includes an 8-month fallow period followed by at least 6-months of crop establishment with limited ground cover. Soil left bare is highly erodible due to intensive tillage required to terminate the old ratoons and plant the new seed cane, as well as annual rainfall amounts exceeding 1650 mm [2]. Many farmers in the US grow sugarcane as a monoculture, a practice that may limit profitable and sustainable productivity. Soil is degraded by the monoculture practice; it is more compacted [4], contains less organic matter [5], and abundant root pathogens that are harmful to crop health, including

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