Tuesday, November 14, 2006

Spinach growth and yield response to reduced fertilizer application and irrigation.

Konanani B. Liphadzi, Martin Maboko, and Jan Viljoen. Agricultural Research Council-Roodeplaat, Vegetable and Ornamental Plant Institute, Private Bag x293, Pretoria, South Africa

Both soil fertility depletion and drought are major causes of declining food production on resource poor farmer’s holdings in sub-Saharan Africa. Due to the high cost of agricultural inputs, low input production systems may be more suited for resource poor farmers. A field experiment was conducted at the Agricultural Research Council-Roodeplaat Institute (South Africa) to determine the effect of reduced fertilizer application and irrigation on growth and yield of spinach (Spinacia oleracea L.). Spinach seedlings were planted into rows spaced 40 cm apart while within row spacing of 15 cm was used. Six fertilizer treatments applied were: nitrogen only, applied at 110 kg ha-1 (N1x), NPK applied at a recommended rate of 110, 30 and 100 kg ha-1 for N,P and K , respectively (F1x), NPK applied at half the recommended rate (F½x), NPK applied at a quarter of the recommend rate plus compost applied at half recommended rate (FC), compost applied at the recommended rate (C1x) and a control where no fertilizer was applied (0x). Using a drip irrigation system, irrigation treatments were (1) the amount of water need by soil to reach field capacity (100%) and (2) 70% of the field capacity. A hand held soil moisture probe was used to monitor soil moisture. Preliminary results showed that the number of leaves, leaf area and plant biomass were higher in the N1x and F1x treatments than in other treatments. Highest cumulative spinach yield was obtained in the N1x treatment followed by the F1x and C1x treatments while yields were comparable between the F½x, FC and the control treatments. Spinach yield was higher when 100% moisture was applied than when 70% was applied. Spinach nutritional quality was not affected by either fertilizer or irrigation treatments.