Effect of organic management methods on yield and quality of carrot and on weeds


On December 17th starting at 10:15 doctoral student Ingrid Bender​ will be defending her thesis „Effect of organic management methods on yield and quality of carrot and on weeds​."

The thesis covers two organic studies. The first one aimed to estimate organic carrot yield and quality in comparison of conventional production. Comparison of vegetable production systems has often provided inconsistent results as fertilization rates have been higher in conventional production. This thesis deals with two different fertilization regimes: (1) optimal level of nitrogen (N) fertilization in both systems (TP1); (2) below optimal N fertilization only in organic production (TP2).

Quality studies consisted of the determination of the content of total sugars (TS), vitamin C, dry matter (DM), N, nitrate (NO3) and pesticide residues in carrots. The second research aimed to study the effect of rolling-crimping technology (RC) on weed density, weed species richness and weed community in organic vegetable no-till cultivation. For the first time in Estonia, RC technology was used and compared with green manure technology (GM). RC technology crushed or crimped the stems of agroecological service crops (ASC) and retained the residues as mulch on the soil surface thereby suppressing weeds during the cultivation period of the cash crop (cabbage).

The results showed that significantly higher marketable yield and lower discarded yield in organic management in TP1 was produced. Despite below optimal N fertilization level in TP2, the marketable yield was on the same level and discarded yield was lower in organic treatment compared to these in conventional treatment. These advantages of organic production over conventional can be explained by the influence of compost on the soil properties compared to the synthetic fertilizer.

The content of vitamin C was higher in organically produced carrots in TP1. No significant differences in content of TS, vitamin C and DM were found between organic and conventional treatment in TP2. Conventionally produced carrots had a higher N content only in TP2 and a higher content of NO3 than organic carrots in both trials. Pesticide residues were found in conventional carrots of both trials. RC technology reduced weed density and weed species richness but increased the share of perennial weeds compared to GM.

Supervisors are  prof. Emeritus Anne Luik, associate professor Evelin Loit and Ilmar Tamm (Estonian Crop Research Institute), opponent is Dr.Terhi Suojala-Ahlfors (Natural Resources Institute Finland). Abstract is available in Library of Estonian University of Life Sciences DSpace archive