CA RESEARCH HIGHLIGHTS ICRISAT

Esther N. Masvaya and Kizito Mazvimavi

Research

• Crop yield and weed growth under conservation agriculture in semi-arid Zimbabwe

• Effect of hand-hoe based conservation agriculture on soil fertility and maize yield in selected smallholder areas in Zimbabwe

• Effect of tillage method and fertiliser application rate on maize growth and yield

• Disaggregating the effects of conservation agriculture : impact on soil moisture crop growth and yield

…research

• Meta Analysis: Effect of conservation agriculture on maize yield in the semi-arid areas of Zimbabwe.

• Effect of planting basin size on maize growth and yields

• The potential of maize-cowpea intercrops to increase crop productivity under reduced tillage in the semi-arid areas of Zimbabwe

Main Research Findings

Effect of hand-hoe based conservation agriculture on soil fertility and maize yield in selected smallholder areas in Zimbabwe

NR IIa

pH

3.0

3.5

4.0

4.5

5.0

5.5

6.0

6.5

7.0

NR IIb NR III NR IV

Organic C

(g kg-1

)

0

5

10

15

20

25

Total P (g kg

-1)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

n = 30 n = 43 n = 37 n = 75

Figure 1. Box plots presenting ranges in soil pH, organic C and total P in planting basin-based CA and conventionally tilled plots across contrasting agro-ecological natural regions in Zimbabwe. The mean lines present the agro-ecological average of the respective soil property

The high variability in soil pH, organic C, total N and P across tillage treatments and natural regions was attributed to high variability in the soil types over short distances.

Figure 2: Infiltration rates of sandy soils under conventional tillage and different CA practices in sub humid smallholder areas in Zimbabwe.

Effect of hand-hoe based conservation agriculture on soil fertility and maize yield in selected smallholder areas in Zimbabwe

• Planting basins alone had no effect on infiltration rate compared to conventional tillage; in fact steady state infiltration rate was higher under the latter.

• Combining planting basins with mulching only increased initial infiltration rate but combining the basins with legume rotation increased both initial and steady state infiltration rate when compared with conventional tillage.

• However, the largest increase in both initial and steady state infiltration rate occurred when all the three CA principles were practised

Crop yield and weed growth under conservation agriculture in semi-arid Zimbabwe

Weed Biomass Kg ha-1

Tillage -1WAP 1WAP 4WAP 9WAP 13WAP Total

Plough 8.9 1.8 20.0 13.6 5.0 29.9

RIP 10.2 5.8 22.3 14.5 6.0 34.8

PB 14.4 7.3 26.0 14.7 7.1 40.3

Mulch

0 t ha-1 12.3 5.6 24.9 11.5 16.4 34.2

4 t ha-1 11.4 4.2 21.8 14.2 21.3 35.3

8 t ha-1 9.7 5.0 21.6 17.1 18.6 35.7

Weeding intensity

Low (~2 times)

10.6 5.2 31.6 16.8 9 47.7

High (~4times)

11.6 4.6 14.0 11.8 3 22.3

Crop yield and weed growth under conservation agriculture in semi-arid Zimbabwe

Grain yield kg ha-1 Stover yield kg ha-1

Tillage

Plough 4159 4801

RIP 3662 3180

PB 2602 2168

Mulch level

0 tha-1 3871 3072

4 tha-1 3282 3525

8 tha-1 3271 3552

Weeding intensity

Low (~2 times) 3113 2937

High (~4 times) 3836 3829

• A positive correlation between weed growth and number of years fields have been under planting basins as currently practiced by farmers implies that there is no reduction in weed pressure as expected.

• There is need to explore the use of herbicides, mulch and or cover crops as part of an integrated weed management package in order to reduce labor demand and enable farmers to benefit from higher crop yields and labor investment under planting basins.

Crop yield and weed growth under conservation agriculture in semi-arid Zimbabwe

Disaggregating the effects of conservation agriculture : impact on sorghum grain yields (2012/13 season)

Mulch Level (t ha-1) 0 2 4 Mean

PLOUGH 3028 2833 2778 2880

RIP 2766 2932 2639 2779

PB 2968 2918 2802 2896

P Value Tillage 0.939      

P Value Tillage & Mulch 0.994      

LSD Tillage 0.05 979.2      

LSD Tillage and Mulch0.05 1258.8      

Grain yield (kg ha-1) under different tillage and mulch levels

Meta-analysis of conservation agriculture trials by ICRISAT

Number of Experiments

Weighted mean differences in maize grain yield between CA and CONV, planting basins left and ripper right, experiments are arranged in chronological order (2005-2010) along the horizontal axis

Planting basinsn=81

Weigh

ted

mea

n di

ffer

ence

s (t

ha-1

)

-2

-1

0

1

2

Rippern=44

-2

-1

0

1

2 Yield performance under CA is influenced by soil type, rainfall amount and distribution, inorganic fertiliser and manure application

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