ENVIRONMENTAL IMPACT OF FERTILIZERS IN THE WATER QUALITY OF RAWA PENING

Abstract

ABSTRACT One of the problems faced by Rawapening Lake was the vast presence of water hyacinth plant in the lake. It had covered around 30% of the lake’s surface. This contributed to the silting process in the lake, thus threatened its existence. The rapid growth of water hyacinth in the lake was because the plant absorbed nitrogen and phosphate substances that came into the lake from the chemical fertilizers used in rice fields in the upstream areas of the lake. The objectives of study are to measure the load of nitrate and phosphate in Rawa Pening Lake, three of its input rivers (Panjang, Rengas, Galeh) and output river (Tuntang) and to study the environment impact of nitrate and phosphate from fertilizers in Rawa Pening Lake. This quantitative research was conducted by taking water samples from Rawa Pening Lake, three of its input rivers, and the output river. Also taken was sample of water hyacinth from the lake. Samples were taken at five places in each location to be mixed later on to represent a single sampling point. River flow rate were also measured. The measurement of nitrate and phosphate concentration in the input and output rivers of the lake showed that the highest concentration of nitrate was found in Tuntang River at 0.21 mg/l, and phosphate in Galeh River at 0.153 mg/l. Also, output river (Tuntang) had a lower daily load of (N) and (P) than the load found in the input rivers (144.24 kg (N) and 21.93 kg (P) compared to 289.92 kg (N) and 144.2 kg (P) respectively). This means that there was accumulation of (N) and (P) in Rawa Pening Lake, which caused the rapid growth of water hyacinth plant. This study recommends that water in Rawa Pening Lake and its input rivers be used for irrigation in paddy fields to reduce the consumption of fertilizers needed. This is to minimize the amount of nitrogen (N) and phosphorus (P) that go into the river and the lake. Keywords: Rawapening, water hyacinth, nitrogen, phosphate. ABSTRAK Salah satu masalah yang dihadapi oleh danau Rawapening adalah keberadaan tanaman eceng gondok di danau. Tanaman ini telah menutupi sekitar 30% permukaan danau. Ini memberikan kontribusi terhadap proses pendangkalan di danau, sehingga mengancam keberadaannya. Pesatnya pertumbuhan eceng gondok di danau terjadi karena tanaman eceng gondok menyerap zat nitrogen dan fosfat yang masuk ke danau sebagai akibat dari penggunaan pupuk kimia yang digunakan di sawah-sawah di wilayah hulu danau. Penelitian ini bertujuan untuk mengkaji seberapa besar beban nitrat dan fosfat sisa yang terbuang ke 3 sungai (Panjang, Rengas, Galeh), dan yang ada di Rawa Pening, serta yang keluar dari Rawa Pening, serta seberapa besar dampaknya terhadap Rawa Pening tersebut. Penelitian kuantitatif ini dilakukan dengan mengambil sampel air di 3 sungai, di Rawa Pening serta di Sungai Tuntang, serta mengambil sampel eceng gondok. Masing-masing lokasi diambil di lima tempat, untuk kemudian di campur mewakili satu titik sampling. Laju alir sungai juga diukur. Pengukuran kadar konsentrasi nitrat dan fosfat menunjukkan konsentrasi nitrat tertinggi terdapat di Sungai Tuntang (0.21 mg/l), dan konsentrasi fosfat tertinggi di Sungai Galeh (0.153 mg/l). Sungai-sungai yang bermuara ke Rawapening memiliki kandungan (N) dan (P) yang lebih besar daripada sungai yang mengalir keluar dari Rawapening (144.24 kg (N) dan 21.93 kg (P) banding 289.92 kg (N) dan 144.2 kg (P). Ini berarti bahwa ada akumulasi nitrogen (N) dan fosfat (P) di danau Rawapening, yang menyebabkan pesatnya pertumbuhan eceng gondok. Penelitian ini merekomendasikan agar air danau dan sungai Panjang, Galeh dan Rengas digunakan kembali untuk irigasi di sawah untuk mengurangi konsumsi pupuk yang dibutuhkan. Hal ini untuk meminimalkan jumlah nitrogen (N) dan fosfat (P) yang masuk ke dalam sungai dan ke danau. Kata kunci: Rawapening, eceng gondok, nitrogen, fosfat.