Crop response to soil water content under fertilized and non-fertilized conditions
Gachene, C.K.K.(University of Nairobi, Department of Soil Science, Nairobi, Kenya) | Mbuvi, J.P.(University of Nairobi, Department of Soil Science, Nairobi, Kenya) | Linner, J.(Swedish University of Agricultural Sciences, Department of soil sciences, Sweden) | Jarvis, N.(Swedish University of Agricultural Sciences, Department of soil sciences, Sweden)
Observations on crop response to soil water content were made over a 2-year period from 1991 to 1992 on 3m by 10m plots at Kabete, Kel1ya. The total anmial rainfall was 948 and 1125mm in 1991 aind 1992 respectively with 101 and 90 rainy days respectively. Two plots, each replicat¬ed two times were cropped to continu~us maize (Zea mays L.) for four seasons ahd were either fertilized or non-fertilized' Due to the more vigorous crop growth] in the fertilized plots, a higher rate of soil water depletion was noted than in non-fer¬tilized plots at both 20cm and 50cm depth. Crop water stress index values also confirmed this observation. The CWSI taken on 3.4.92 were 630 and 813 for fertilized and non-fertilized crop respectively. The difference in soil water content between fertilized and non-fertilized crops was more pronounced at 50cm depth indicating that the former crop had a well developed root system in the subsoil. In particular, most of the available water was left unuti¬lized during the growing period of 1992 short-rains in the non-fertilized plots. During the four seasons, the fertilized crop generally reached tasselling two to two and a half weeks earlier than the non-fertilized crop. Average maximum crop height, LAI and maize grain and above-ground dry matter yields during the four seasons were 245cm, 5.08, 5555.6 kg and 12,110.7 respec¬tively for fertilized crop. The correspond¬ing figures for non-fertilized crop were 191 em, 3.44, 3305.6 kg ha-l and 6,623.4 kg ha-l.
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