This document summarizes a multi-phase study on weed competition and conservation agriculture for smallholder maize farmers in Nepal. A farmer survey found labor constraints and heavy weed pressures. On-farm trials showed weed populations were much higher than recommended thresholds and that maintaining the recommended maize crop population density increased yields by over 160% compared to farmer practices. Ongoing on-station trials are evaluating no-till and residue retention practices with fertilizer amendments on maize-rice rotations.
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Importance of Conservation Agriculture in Nepal
1. Weed competition and conservation
agriculture for smallholders: Insights from
maize systems in the hills of Nepal
Tika Karki1
, Andrew McDonald2
and Adam Davis*3
1
Tribhuvan University, Kathmandu; 2
CIMMYT, South Asia Regional
Office; 3
USDA-ARS Global Change and Photosynthesis Research Unit
20. BMP: 52,000 plants +/- 150 ha-1
Farmer: 36,900 +/- 500 plants ha-1
BMP Farmer
Crop population (practice)
0
1
2
3
4
Yield(Mg/ha)
Maintaining maize crop
at recommended population
density resulted in a yield
increase of over 160%
compared to the farmer
practice of heavy thinning.
21.
22.
23. On-station trial (2009-present)
• Maize-rice crop rotation
• Split plot design with full factorial of:
– Tillage (main): no-till, conventional (ox-drawn
plow)
– Residue Retention (split): removed, 40 cm
– Soil fertility (split-split): farmer practice (FYM),
BMP: FYM + Urea (110 kg N ha-1
)
Notes de l'éditeur
This slide basically says it all: topography, climate, socioeconomic trends, technology
Crops should be planted in March to take full advantage of rains. Out-migration of labor has made timely planting difficult, and it is often delayed by as much as a month.
The survey sites in the mid-hills of Nepal are located at 1100-1500 m above sea level.
This is a typical village in the mid-hills of Nepal. It looks idyllic, but the lush fields hide a grim reality: food security is tenuous in the region. Most of the surveyed households had less than 6 months food self-sufficiency, and little income to purchase additional food. This has led to a large outmigration of labor from the villages to the cities, compounding the difficulty of completing agronomic operations in a timely way.
This farmer is standing in a maize-fingermillet relay cropping system, which was the dominant cropping system in the surveyed villages. Everyone here knows what maize looks like. Fingermillet is less common to us.
This is a finger millet nursery. Finger millet seedlings are transplanted into maize after ‘earthing up’, or inter-row cultivation (done by bullock or hand).
“Once harvested, the seeds keep extremely well and are seldom attacked by insects or moulds. The long storage capacity makes finger millet an important crop in risk-avoidance strategies for poorer farming communities.” Wikipedia
Lower right: dosas made from finger millet flour
An important point of sampling in the study was to make sure to include women respondents, as they contribute much of the on-farm labor, including fertility management (through gathering of farmyard manure) and hand weeding.
These results are over the past 5 years
The weed pressure in this field is typical of what we observed in farmers fields:
The story is similar for finger millet.
Villagers start off with high crop stands, but these taper off over the course of the growing season as maize is thinned for fodder.
Much of what we’re doing on the system is still basic agronomy. But we’re trying to do this within the context of a conservation agriculture system to determine whether the increased water savings from such a system are compatible with acceptable weed management.
The data are still coming in for the field trial, but as you can see from this picture, maize in the CA system continues to have good access to soil moisture even when rainfall is limited. In contrast, the maize in the conventional system appears drought-stressed.
In summary, the low yields of the current cropping system stem from difficult environmental conditions, outmigration of labor and low mechanization levels. Moving in the direction of conservation agriculture may help by easing water shortages, but appropriate technology, including improved cultivars and scale-appropriate mechanization will be critical to increasing food stability. Here is a simple two-row planter that can be easily transported among the terraces. A simple change, such as creating regular crop geometries, will enable a host of other efficiencies.
