Volcanic fertilization of Balinese rice paddies

Abstract Since the advent of high-yielding ''Green Revolution'' rice agriculture in the 1970s, Balinese farmers have been advised to supply all the potassium and phosphate needed by rice plants via chemical fertilizers. This policy neglects the contribution of minerals leached from the volcanic soil and transported via irrigation systems. We documented frequent deposition of volcanic ash deposits to rice producing watersheds. Concentrations of phosphorus in rivers were between 1 and 4 mg l − 1 PO 4 , increasing downstream. We measured extractable potassium and phosphate levels in the soils of unfertilized Balinese rice paddies, and found them to be indistinguishable from those in fertilized paddies, and sufficient for high grain yields. Field experiments varying phosphorus applications to rice fields from 0 to 100 kg superphosphate per hectare (7-26 kg P ha − 1 ) demonstrated small increases in harvest yields only with the smallest additions. Direct measurements of PO 4 in irrigation waters indicate that most of the added phosphate flows out of the paddies and into the river systems, accumulating to very high levels before reaching the coast

Optimizing Native and Landscape Plant Establishment Under Marginal Soil and Water conditions in Southwestern Deserts

Two aspects of salinity in arid land were investigated as part of the present dissertation: the first was the potential re-use of industrially generated brine for irrigating landscape plants, and the second was the ecological restoration of saline farmland. The following is a summary of the most important points. With water conservation efforts accelerating in arid environments, industrial wastewater is considered a candidate for re-use. We investigated the use of high EC (electrical conductivity) cooling-tower water to irrigate nine common landscape plants in an urban environment. Each plant (replicated in a block design) was irrigated according to water demand determined by the soil moisture deficit, with one of three water treatments: blowdown water (3.65 dS m⁻¹), well water (0.52 dS m⁻¹) and a 1:1 blend (2.09 dS m⁻¹). Results indicate the salinity of the irrigation water did not have a significant effect (P>0.05) on growth or water use but, soil salinities were higher in basins irrigated with blowdown water compared to those irrigated with well water. The overall feasibility of reusing industrial brines to irrigate urban landscapes is discussed in light of the results. Restoring abandoned arid farmland can be challenging because topographic, geomorphic and hydrologic features have been degraded and cannot support a diverse native plant community. Typical amelioration practices depend upon good quality water to restore the soil’s physiochemical properties, however the long-term availability of any water is rare. A mitigation banking project to return 432 hectares of farmland to an open-space designation involved the collaboration of scientists, landscape architects and engineers to achieve five main goals: water management, erosion control, decreasing soil salinity, and increasing species diversity and vegetation cover. Two strategies evolved in the planning process that work in tandem to achieve these goals: a water management system that redirects storm water and run-off to discrete areas of the site for subsurface storage as plant-available water, and the introduction of a diverse mix of native plants. Field trials tested the strategies and also investigated different soil surface treatments, seeding methods and irrigation regimes against the germination and establishment of a customized native seed mix. Results from vegetation data indicate a combination of soil ripping and imprinting leads to the highest germination and establishment rates and drip irrigation helped establish transplanted seedlings. The project was designed so the longterm outcome does not depend on continual inputs and maintenance