Termite prevalence and crop lodging under CA in semi-arid Zimbabwe. Eleanor Mutsamba
Termite Prevalence and Crop Lodging underConservation Agriculture in Semi-arid Zimbabwe By Eleanor F Mutsamba, Nyagumbo, I, and Mafongoya, P.M Dpt of SSAE-UZ CIRAD
IntroductionBenefits of termites: food, improve soil propertiesBenefits of crop residues: Opinions on retention of crop residues• retention of crop residues contribute to increased termite prevalence thus lodging in semi-arid regions.• the presence of dry crop residues may actually reduce termite attack on growing crops Q. At what residue application rate can they reduce termite attack on crop if applied at the start of the season? This study therefore sought to establish the linkage between termite prevalence, crop residues, crop lodging and crop yields.
Specific objectives• To establish the influence of surface applied crop residues on termite prevalence in CA systems• To determine the contribution of crop residues applied as a surface mulch to crop damage by termites in CA systems.
Materials and Methodsproject site: Kadoma (NRIII) Field lay out:• A Complete Randomised Block Design (CRBD) experiment• 5 treatments of (0, 2, 4 and 6 t ha-1 of crop residues under CA) and a control (conventional mouldboard ploughing treatment), 4 replicates per treatment per farmer.• Maize residues used
Methodology cont….. Sampling procedures• soil monoliths measuring 20 cm x 20 cm x 20 cm depth were used sample termites• Crop damage was assessed by counting number of lodged plants by termites in each plot. Result expressed as % of total plants
Table 1: Effects of different residue amounts under CA on termite abundance (per m2 of soil) compared to under CMP a 2008/9 2009/10 Treatments CA- 0t/ha residue cover 300 a 283 a CA- 2t/ha residue cover 2100 b 263 a CA -4t/ha residue cover 3050 b 1179 b CA- 6t/ha residue cover 2662 b 1121 b CMP 25 a 358 a LSD 1724 612 Means followed by the same letters in a column do not significantly differ at 5% level, LSD test
Table 2: Percentages of lodged crops under CA at different residue amounts compared to CMP. a Means followed by the same letters in a column do not significantly differ at 5% level, LSD test
Table 3: Crop yield (kg/ha) under CA with different residue amounts compared to CMP 2008/09 2009/10TreatmentsCA- 0t/ha 2900 a 2348 aCA- 2t/ha 3055 a 2814 cCA- 4t/ha 3034 a 2693 bcCA- 6t/ha 3348 a 2756 bcCMP 2117 b 2570 abLSD 750 222Means followed by the same letters in a column and within site do not significantly differ at 5% level, LSD test
DiscussionSignificance at 4t/ha to CMP wrt termite numbers:• residues attract termites and act as food source• Tillage disturbs termites’ channels and nesting sites
Discussion• No trend in crop lodging as residue amount increases: by time of harvest all termites were already finished.• Lower lodging on CMP compared to CA could confirm that tillage disturbs termites channels• Lodging in maize reached about 40 % which is too high• The inconsistence of yield under CA as crop residues app. rate increases was also observed by CIMMYT, Zim•
Conclusion• Increasing crop residues under CA increased termite numbers with highest peak at 4t/ha.• Addition of crop residues did not necessarily reduce crop lodging in a notable pattern. This is so because by the time of physiological maturity, all the residues would have been finished.• Increasing crop residues had no sign. effect on yield at least in the short term
Recommendations• there is need for termite control and early harvesting in t.i.a.• Need for long term (>2 years) local studies