Input and output of major nutrients under monocropping sisal in Tanzania

✍ Scribed by A. E. Hartemink

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 122 KB
• Volume: 8
• Category: Article
• ISSN: 1085-3278
• DOI: 10.1002/(sici)1099-145x(199712)8:4<305::aid-ldr261>3.0.co;2-0

✦ Synopsis

A semiquantitative nutrient balance is presented for a ®eld monocropped with sisal on Ferralsols in Tanzania. Input of nutrients included wet deposition, non-symbiotic nitrogen ®xation and nutrients added with planting material. Nutrient output consisted of the harvested product. The average annual shortfall between 1966 to 1990 was 12 kg N ha À1 , 2 . 8 kg P ha À1 , 38 kg K ha À1 , 44 kg Ca ha À1 and 19 kg Mg ha À1 . The nutrient balance was compared to changes in topsoil (0±20 cm) nutrient contents of the sisal ®eld during the same period. Average annual decrease in soil nutrient contents was: 104 kg N ha À1 , 1 . 8 kg P ha À1 , 11 kg K ha À1 , 29 kg Ca ha À1 and 10 kg Mg ha À1 . Much more nitrogen was lost from the topsoil than can be explained by the nutrient balance, indicating signi®cant losses. Changes in soil phosphorus content are almost explained by the nutrient balance. More exchangeable cations were removed with the yield than were lost from the topsoil, which may imply that cations are extracted from the subsoil. Both the nutrient balance and the changes in soil nutrient contents showed that monocropping sisal is mining nutrients.