Study of soil moisture on dryland for three crop plantations in Malang regency East Java means of neutron probe

English. The objective of the work was to assess changes of stored-soil water content in the rooting zones of coffee, cocoa and clove trees. The experiment was carried out at the Research Centre Sumber Asin, Malang. No specific experimental design was adopted. Alluminium access tubes were simply installed at randomly selected sites and measured changes of soil water content using a neutron moisture gauge, at different soil depths over a one year period, to cover rainy and dry seasons. During the dry season from July to September, although the water content within the surface layer (00-45 cm) nearly reached the wilting point, the trees did not show any sign of water stress. The results indicated that the tree roots were more active below 60 cm depth where the stored water content was near to the field capacity year-around, and therefore water-uptake by the trees was not interrupted. During the dry season, drying soil surface acted as a self-mulching layer and presented further evaporation from the surface. Water flow from the deeper wet regions was negligibly small.

Indonesian. Tujuan penelitian ini adalah untuk mengetahui perubahan kandungan lengas tanah di mintakat perakaran tanaman kopi, cacao, dan cengkeh. Percobaan dilakukan di Kebun Percobaan Sumber Asin, Malang, dengan tanpa rancangan percobaan khusus. Tabung aluminium dipasang secara acak pada lokasi percobaan dan perubahan kandungan lengas tanah diukur dengan neutron probe pada berbagai kedalaman selama setahun. Saat musim kering dari bulan Juli sampai September meskipun kandungan lengas tanah di lapisan atas (00 - 45 cm) mendekati titik layu, tetapi tanaman tidak menunjukkan gejala stress. Akar tanaman aktif dalam lapisan di bawah 60 cm di mana lengas tersimpan tetap kondisi kapasitas lapang sepanjang tahun sehingga serapan air oleh tanaman tidak terganggu. Selama musim kering lapisan permukaan tanah yang kering bisa bekerja sebagai lapisan self-mulching dan menahan laju evaporasi. Aliran air dari lapisan bawah lambat sekali dan bisa diabaikan.