Varying Effects of Organic Waste Products on Yields of Market Garden Crops in a 4-Year Field Experiment under Tropical Conditions

Falilou Diallo,Karamoko Diarra,Samuel Legros,Frédéric Feder

doi:10.3390/agronomy12010032

Abstract

Controlling organic and mineral fertilisation is a major concern in tropical environments. An experiment was conducted on an arenosol in the Dakar region, the main market gardening area of Senegal, to evaluate treatments commonly used by farmers. Seven treatments were repeated three times: A mineral fertilisation (MF) treatment based on N-P2O5-K2O (10-10-20), and three organic treatments at two doses (dried sewage sludge (SS), poultry litter (PL) and a digestate from an anaerobic digestion (AD) of cow manures). Each of the organic treatments were supplemented with a normal dose (1) and a double dose (2) of mineral N and K fertiliser. A lettuce, carrot and tomato rotation was grown in four campaigns (2016–2020) on all of the plots. Yields of all three crops in all of the organic treatments were statistically similar (p > 0.05) to the MF in all four campaigns, except for the yield of the lettuce crop under treatment PL-2 in campaigns 2 and 3. The tomato yields were statistically similar under all of the organic treatments in all four campaigns. In contrast, the yields of the lettuce and carrot crops differed statistically from each other and under the different organic treatments in all four campaigns. The yields of all three crops differed in the campaigns with the fertilisation treatment. In each campaign, the yields of each crop were not correlated with the total amounts of N, P and K applied. These differences or similarities in yields are explained by the nature of the organic waste products, the accumulation of nutrients after several applications, the type of crop and interannual differences in temperature.

Highlights

Recycling organic waste products (OWPs) in agriculture sustains the ecosystem services provided by soils and achieves yields at least equivalent to those obtained with mineral fertilisers [1]
Our results show that they can carry out different organic fertilisation treatments that will enable them to obtain yields equivalent to those obtained with an entirely mineral fertilisation
For the lettuce and carrot crops, better yields were measured with high doses of poultry litter

Summary

Introduction

Recycling organic waste products (OWPs) in agriculture sustains the ecosystem services provided by soils and achieves yields at least equivalent to those obtained with mineral fertilisers [1]. Crop yields obtained with OWPs are frequently compared to those obtained with mineral fertilisers [2,3]. Most authors studied the immediate effects of OWPs and their residual effects on yields by adding them only once at the start of the experiment in (i) trials with unbalanced N, P and K, compared to mineral fertiliser (ii) tests with balanced N or P, (iii) tests with balanced N and P or balanced P and K and tests with balanced N, P and K [2,4,5]. Other authors demonstrated the effects of the repeated application of OWPs on yield usually with one or two applications per year, most often on field crops in monoculture or in rotation with two or three plant species [6,7,8,9]. Few studies have evaluated the effects of OWPs in intensive systems with regular applications, vegetable crops over a period of several years.

Methods

Results

Discussion

Conclusion