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Rice (Oryza sativa) is a staple food crop for over half of the world's population. However, drought as a result of climate change has led to increased soil salinity, thereby reducing agricultural potential, especially rice nutritional compositions and biochemical properties. Nevertheless, soil management by using suitable fertilizers might be able to improve rice quality even though these rice samples were grown in soil with a high degree of salinity. This study investigated nutritional compositions, phenolic contents, and antioxidant activities of twenty-five rainfed rice samples in Khao Dawk Mali 105 (KDML105) and Rice Department 15 (RD15) varieties grown in soil with different degrees of salinity. The soil, however, had been improved by the usage of fertilizer at the tillering and booting stages. Results indicated that all rice samples exhibited similar nutrients, total phenolic contents (TPCs), and antioxidant potentials, suggesting that appropriate fertilizer could improve rice qualities. Principle Component Analysis (PCA) and Pearson correlation results suggested that regardless of rice varieties, organic matter (OM) and soil potassium (Ks) showed a very strong positive correlation with protein and minerals (Ca, Na, K, and Fe), while opposite results were observed with soil pH. Moderate to very weak correlations were also observed between soil parameters and TPCs, as well as between soil parameters and antioxidant activities. The received information will be useful for the future development of appropriate fertilizer usage in salt-tolerant rice with particular nutritional quality. [ABSTRACT FROM AUTHOR]

The study was carried out at the Suphanburi Agricultural Research and Development Center, U-thong district, Suphanburi province during 2009-2011. The soils are classified as Kamphaeng Saen soil series. The objectives were to study appropriate management on slightly saline soil to increase the physic nut yield and to study the effect of soil amendments on changes to the soil's chemical properties. The experimental design was a randomized complete block design with 3 replications. The 10 treatments were: 1) control; 2) chemical fertilizer; 3) compost, 2 kg plant-1 year-1; 4) compost, 4 kg plant-1 year-1; 5) farmyard manure, 2 kg plant-1 year-1; 6) farmyard manure, 4 kg plant-1 year-1; 7) compost, 2 kg plant-1 year-1 + bio-extract; 8) compost, 4 kg plant-1 year-1 + bio-extract; 9) farmyard manure, 2 kg plant-1 year-1 + bio-extract; and 10) farmyard manure, 4 kg plant-1 year-1 + bio-extract. For treatments 2-10, chemical fertilizer (15-15-15) at a rate of 156.25 kg ha-1 was applied. The results showed that utilization of organic fertilizer plus chemical fertilizer resulted in increased growth of physic nut but this was not significantly different from the control treatment. Application of organic fertilizer had no effect on growth and yield of physic nut, however the use of organic fertilizer plus chemical fertilizer tended to give yields higher only than for chemical fertilizer and the control of 1906.25, 1421.69, and 1040.63 kg ha ', respectively, but these were not significantly different. After the experiment, the soil electrical conductivity (ECe) changed slightly. No effect of the organic fertilizer and chemical fertilizer was found, however, variation in the ECe was found. Soil organic matter tended to decrease while the available phosphorus tended to increase. Generally, the available potassium tended to increase except in the control treatment and the treatment with only chemical fertilizer. [ABSTRACT FROM AUTHOR]

Abst ract Rubber tree plantations ( Hevea brasiliensis ) are expanding into marginal areas with low soil fertility and long dry seasons with a high risk of soil erosion and drought damage to trees. Introducing an N 2 -fixing legume cover crop in rubber plantations may reduce runoff and soil erosion as well as increasing the availability of nutrients but may also increase competition for water. This study quantified the effect of the legume cover crop Pueraria phaseoloides on N, P and K nutrition, water status and growth of young rubber trees (three years old in 2007) over a four year period (2007–2010). The plantation was located on a toposequence with a range of soil depths and water storage capacities in northeast Thailand. The legume aboveground biomass production and its nutrient content and decomposition rate were measured and the N 2 fixation was estimated using the abundance of 15 N (δ 15 N) in the legume. Measurements were taken of the tree stem girth and height and tree leaf predawn water potential, nutrient content and greenness. The transfer of N 2 fixed by the cover crop to the trees was estimated using δ 15 N in the tree leaves. The annual biomass production of the legume was 8 Mg ha −1 year −1 and the N accumulation by the legume was 250 kg N ha −1 year −1 . The natural abundance method applied to the aboveground components of the legume gave N 2 fixation rates varying from 85 to 93% depending on the year. The leaf δ 15 N was similar in the three non-legumes ( H. brasiliensis , Vetiveria zizanioides and Praxelis clematidea ) used as reference plants for estimating the N 2 fixation. The higher level of N and the much lower leaf δ 15 N values for the rubber trees intercropped with P. phaseoloides , compared to rubber trees growing without a legume cover crop, showed that there was a relatively high transfer of fixed N from the legume to the trees, varying from 39% to 46% of tree leaf N depending on the year. Neither N 2 fixation nor N transfer varied significantly along the toposequence. At the bottom of the toposequence, both the nutrient (N, P and K) and water status of trees was significantly improved with the legume cover crop, doubling the tree girth at seven years of age (tree girth: 28 cm, tree height: 700 cm). However, at the top of the toposequence with low water storage capacity, the legume cover crop improved tree nutrition and growth but reduced the trees' ability to survive intense drought. These results raise concern about the resilience to drought of the rubber tree/ P. phaseoloides system, since the positive effect of the legume on rubber tree nutrition and growth may increase the risk of water stress and tree mortality. With future changes in climate, an increasing number of areas will be concerned by the question of optimizing the tradeoff between N inputs and water availability. [ABSTRACT FROM AUTHOR]