Effects of Different Plough Depths on Growth and Yield of Tomatoes (Solunum Lycopersicon)

CHAPTER 1: INTRODUCTION
1.0 INTRODUCTION
Tomatoes (Solanum lycopersicon) belong to the Solananceae family and are widely grown in Zimbabwe as a vegetable. It is a perennial crop but is grown as an annual both at commercial and smallholder level of production in Zimbabwe. Tomatoes originated in Peru, Bolivia and Ecuador area of the Andes mountains and spread throughout the world during the Spanish colonisation of the Americas in the 17th century and were regarded as food around 1835 according to Perelta, 2007. Tomatoes are consumed in many ways which include eating them raw as a fruit in salads, in soups, as fruit juice and can be breaded fried as green tomatoes. Jose (2012) highlighted that tomatoes are an excellent source of Vitamin C, potassium, calcium, folate and lycoperne. With lycoperne, tomatoes reduce the risk of breast cancer, head and neck cancers and is strongly protective against neurodegenerative diseases.
The tomato plant has the potential of yielding up to 300 tonnes/ha depending on variety as stated by Oslom (2012). However, farmers are not attaining this potential yield due to several factors which include pest and diseases, inadequate rainfall or irrigation water, exterme temperature and shallow plough depth or small pot size.   NeSmith et al (2002) pointed out that yield of most crops and vegetables is affected by plough depth in Zimbabwe.
Farmers are establishing their crops in shallowly tilled land resulting in restricted root penetration into the soil thereby resulting in reduced root volume, Saoirse et al (2012). Reduced root development results in reduced nutrient and water uptake hence affecting growth and development. Root restriction can result in reduced formation of aerial dry matter which lowers the photosynthetic capacity of the crop and ultimately lowers yields.
Bangerth et al, 2000 expressed that there is interdependence between shoots and roots. Roots rely upon plant aerial portions for photoassimilates and various hormones while...