Humic acid (HA) has been reported to increase plant growth and crop yields, as well as improve soil fertility. However, the potential utilization of HA extracted from various organic waste composts as organic amendment in suboptimal soils has not been studied in depth. The experiment used a two-factor Completely Randomized Design (CRD) with three replications. Four types of HA were used, namely bagasse HA (BHA), water hyacinth HA (WHA), market waste HA (MHA), and commercial HA (CHA). It also comprised of four doses HA i.e., 0.05, 0.10, 0.15 and 0.20% (of soil on w/w base). The results revealed that fluctuations in soil pH and nutrient release with the HA application had a variable quadratic response pattern. Organic carbon increased by 17%, while total N and available P decreased by 5% and 38.6% during the last weeks of incubation. The HA application could improve the growth response and nutrient uptake of maize significantly. CHA0.20% was the best interaction treatment which had the highest average value on dry weight and NPK uptake, which were 98.0 g pot-1, 178.8 mg plant-1, 27.4 mg plant-1 and 216.9 mg plant-1, respectively. The scanning electron microscopic (SEM) showed that HA could increase in the length and density of maize root hairs. Furthermore, the HA application significantly increased pH, CEC, C-organic content and availability of soil nutrients.

<p class="Abstract">This research aimed to determine the effect of various organic fertilizer and watering intervals on plant growth and tomato yield, also soil nutrient content. The method used was factorial completely randomized design with a combination of organic fertilizer types (kaliandra compost, water hyacinth and Mexican sunflower compost, cow manure and straw compost, and vermicompost) and watering intervals (1, 3 and 7 days). Mycorrhizal dose used was 2 grams/plant, while organic fertilizer used was 160 g/plant. The results showed that the interaction between organic fertilizer and watering intervals did not affected significantly on tomato plant height, stem diameter, root length, initial flowering, fruit diameter, number of fruits and fresh fruit weight and soil nutrient content. Watering interval affected significantly to all parameters of the observation. Addition of organic fertilizer can increase soil C-organic content by 6.58% and P-available by 170.51% compared to controls. In general, the highest tomato production was obtained in the combination of treatments water hyacinth and Mexican sunflower compost and watering interval of 1 day, which was 231 g/plant or equivalent 7.22 tons/ha.</p>

Pemanfaatan lahan rawa di Indonesia memiliki peranan penting dan strategis bagi pengembangan pertanian terutama mendukung ketahanan pangan Nasional. Hal ini disebabkan oleh luas lahan rawa yang berpotensi untuk dijadikan lahan pertanian khususnya tanaman padi masih tersedia cukup luas. Lahan rawa merupakan salah satu lahan suboptimal yang memiliki kendala secara alami kesuburan tanahnya tergolong rendah. Oleh karena itu penting dilakukan pengkajian untuk mengetahui potensi pemanfaatan lahan rawa di Kab. Lingga, Kepulauan Riau untuk digunakan sebagai lahan pertanian padi sawah. Kajian ini merupakan action research menggunakan lahan seluas tiga hektar sebagai demplot pertanaman padi yang terletak di tiga kecamatan utama di Pulau Lingga. Berdasarkan hasil kajian, diketahui bahwa: (1) kendala utama pengembangan lahan rawa lebak adalah genangan maupun kekeringan yang belum dapat diprediksi dan reaksi tanah yang bersifat sangat masam-masam, serta status hara yang tergolong rendah-sedang dan (2) hasil panen menggunakan varietas INPARA 5 masih tergolong rendah, sekitar 0.5-2.5 ton/ha. Produksi padi pada lahan rawa lebak masih berpeluang untuk dikembangkan dan ditingkatkan dengan melalui penerapan teknologi spesifik lokasi, terutama inovasi pengelolaan air, hara dan tanaman secara terpadu, serta dilakukan pembentukan kelembagaan petani.