Exploration of agro-ecological options for improving maize-based

215 Pages·2013·2.65 MB·English

Exploration of agro-ecological options for improving
maize-based farming systems in Costa Chica, Guerrero,
Mexico

Diego Flores Sánchez
Thesis committee

Promotor
Prof. dr. M.J. Kropff
Professor of Crop and Weed Ecology
Wageningen University

Co-promotors
Dr. ir. W.A.H. Rossing
Associate professor, Farming Systems Ecology Group, Wageningen University

Dr. ir. E.A. Lantinga
Associate professor, Farming Systems Ecology Group, Wageningen University

Other members
Prof. dr. ir. R. Rabbinge, Wageningen University
Prof. dr. E. Hoffland, Wageningen University
Prof. dr. S. de Neve,Ghent University, Belgium
Prof. dr. ir. O. Oenema, Wageningen University

This research was conducted under the auspices of the C.T. de Wit Graduate School for
Production Ecology and Resource Conservation
Exploration of agro-ecological options for improving
maize-based farming systems in Costa Chica, Guerrero,
Mexico

Diego Flores Sánchez

Thesis
submitted in fulfillment of the requirements for the degree of doctor
at Wageningen University
by the authority of the Rector Magnificus
Prof.dr. M.J. Kropff,
in the presence of the
Thesis Committee appointed by the Academic Board
to be defended in public
on Tuesday 10 September 2013
at 11 a.m. in the Aula.
Diego Flores Sánchez
Exploration of agro-ecological options for improving maize-based farming systems in
Costa Chica, Guerrero, Mexico
215 pages

PhD thesis,Wageningen University, Wageningen, NL (2013)
With summaries in English, Dutch and Spanish

ISBN: 978-94-6173-675-8
To my dear wife Lupita
and my handsome son Diego André
To the memory of my parents

Abstract

In the Costa Chica, a region of Southwest Mexico, farming systems are organized in
smallholder units. The dominant cropping systems are based on maize (Zea mays L.),
either as monocrop or intercropped with roselle (Hibiscus sabdariffa L.). Continuous
cropping, and unbalanced fertilizer management systems with an inadequate
replenishment of organic matter stocks have caused depletion of soil fertility and low
crop yields. This thesis aimed to evaluate alternative cropping systems in terms of their
contribution to on-farm productivity and to regeneration of the soil resource base. A
set of approaches including farm surveys, on-farm experiments and model-based
calculations was applied to characterize farming systems, identify main livelihood
constraints and evaluate alternative cropping and farming systems. Main constraints
identified were low yields of the major crops maize and roselle, low levels of nitrogen,
potassium and soil organic matter, low resource use efficiencies, high production
costs, limited marketing opportunities and low prices of products. To address
prevailing production constraints, farmer-managed experiments were established in
two communities within the region. In on-farm experiments the legumes Canavalia
(Canavalia brasiliensis Mart. Ex Benth) and Mucuna (Mucuna pruriens L.var. utilis
(Wall ex Wight) Burk) were intercropped in (added to) maize monocrops and maize-
roselle mixtures. Intercropping did not decrease maize and roselle yields, and resulted
in major reductions of the weed biomass, as well as an increased N uptake by both the
food crops and the cropping system as a whole. In nutrient management trials different
sources of macro-nutrients were evaluated in maize monocrops and maize-roselle
intercrops. The results showed that improvements at field scale are feasible in the short
term. Partial replacement of mineral NPK by organic NPK in the form of
vermicompost, leading to 10-20% lower total N and K inputs, did not result in lower
maize yields or a reduced uptake of N and K. This suggests that the N and K from the
vermicompost were utilized better by the maize crop than from the inorganic fertilizers
due to lower leaching losses. An experiment on decomposition of and N release from
aboveground biomass residues, crop root residues and vermicompost demonstrated
that, although the pattern of decomposition varied depending on the type of organic
material, most of the N was released within the cropping season. Particularly for
vermicompost, only one third of its initial dry mass was decomposed, thus leaving
significant amounts of residues for soil organic matter build-up. Model-based
explorations were developed to assess the consequences of the experimental results at
the field level for whole-farm performance. Results for eight case study farms
demonstrated that changes in crop nutrition and animal husbandry can increase farm
family income and improve organic matter balances. However, strategies to achieve
these goals most effectively were distinct. To maximize family income required
Abstract

fertilizer-based cropping strategies, while rebuilding soil organic matter required
investment in retaining, obtaining and applying sources of organic matter. Farms
responded differently to the explored options, highlighting the need for crop nutrition
strategies that are adjusted to the soil fertility status of individual fields to be most
efficient. The explorations also showed that for six out of the eight farms the minimum
family income standard could not be attained. The results imply that the current
emphasis in policies to support smallholders by fertilizer subsidies requires adjustment
to include promotion of technology development aimed at regeneration of the
degraded resource base and to offer off-farm economic options.

Keywords: farm diagnosis, farming systems, soil degradation, intercropping, maize,
roselle, legumes, nutrient management, vermicompost, crop residues, decomposition,
explorations.
Table of Contents

Chapter 1 General introduction 1

Chapter 2 Diagnosis for ecological intensification of maize-based 21
smallholder farming systems in the Costa Chica, Mexico

Chapter 3 Exploring maize-legume intercropping systems in Southwest
Mexico 61

Chapter 4 Comparison of organic and inorganic nutrient inputs for
productivity enhancement in smallholder maize-based systems
in Southwest Mexico 85

Chapter 5 Decomposition and N contribution of aboveground crop
residues, crop root residues and vermicompost in maize-based
cropping systems in Southwest Mexico 121

Chapter 6 Soil fertility management and crop-livestock interactions as a
way out of poverty? Exploration of farm-specific options for a
region in Southwest Mexico 139

Chapter 7 General discussion 171

Summary / Samenvatting / Resumen 189

Acknowledgements 200

Curriculum Vitae 203

List of publications 204

Educational certificate of the Graduate School PE&RC 205