Sugar-palm (Arenga pinnata (Wurmb.) Merr.) grows naturally under the shade of tree canopies and therefore, shading levels have a main role for its optimal growth. This study was conducted in order to examine the effects of shading on the seedlings growth for up to 11 months under four shading levels: S0 (100% of full sunlight or non-shading), S1 (32% shading level), S2 (56% shading level), and S3 (64% shading level). Sugar-palm seedlings grown under the shade (i.e. 32, 56, and 64%) showed better plant height, stem diameter, leaf size, petiole and rachis lengths, chlorophyll content, fresh and dry root weights, root volume, and total biomass than those grown in direct sunlight. Although there were no significant different responses among the shading treatments on plant height, biomass dry weight, leaf morphological characteristics, chlorophyll content, and SPAD value, the S2 treatment had a significant effect on a better root characteristics. Therefore, it can be concluded that this treatment, i.e. 56% shading level, is the optimal condition for sugar-palm seedlings.
This study examined how slope-related soil physicochemical properties affect the growth and yield of upland rice subjected to slash-and-burn. The yield survey and soil analysis were performed at a hillside farm in Southeast Sulawesi Province, Indonesia. Organic-C, total-N, available-P and exchangeable-Ca, Mg, and K tended to increase further down the slope, leading to greater rice growth and yield. The resultant yield increase was mainly attributable to higher spikelet number per square meter. Total-N explained variation in spikelet number per panicle, but not variation in grain yield. Among the tested soil physicochemical parameters, only organic-C was significantly and positively correlated with rice growth and yield. In addition, most other parameters increased with soil organic-C. These findings indicate that organic-C in the soil is important to the growth and yield of upland rice cultivated with slash-and-burn systems, although other complex relationships may exist between rice productivity, the environment, and agricultural management factors. Moreover, our results imply that position on a slope affect rice growth and yield.
Jatropha curcas L. has attracted worldwide recognitions in recent years, because its seed oil is suitable to substitute for fossil fuels, and it can grow in semi-arid lands. It has been traditionally planted in tropical and subtropical regions, but recent mass cultivation as a biofuel crop is still severally restricted by its low seed production, showing that it is necessary to develop high-yielding varieties. In this paper, to reveal genes or genomic regions underlying yield-related traits, the maker-trait association analysis was conducted in a wide collection of Mexican J. curcas accessions, on the basis of 67 simple sequence repeat (SSR) markers and eight retrotransposon-based insertion polymorphisms (RBIP) markers, by using mixed linear model method (MLM). As a result, eight significant marker-trait associations (MTAs) were found within six traits and six markers. Mean phenotypic variation explained by the markers was 0.24, as indicated by R2 value. Among them, the marker JCG0061, that showed significant associations with fruit weight (R2 = 0.4391) and seed yield per plant (R2 = 0.3151), was identified in a previously-reported interspecific quantitative trait loci (QTL) for the female flower number. This suggests that the genomic region linked to JCG0061 is critical for yield-related traits. Our study would contribute to breeding program for biofuel production and development of J. curcas in tropical and subtropical areas with the semi-arid climate.
Data on four yield components obtained from a long-term experiment, in which NERICA 4 was continuously planted under upland conditions for 17 seasons, were analyzed together with rainfall data. Results showed that rainfalls gave significant positive effects on the number of spikelets panicle-1 (Spikelets), the rate of grain filling (Gf), and 1000-grain weight (Gwt), and yield, but no significant effect on the number of panicles m-2 (Panicles). Of three equally-divided growth periods, the effect of rainfalls during the second period, including the meiosis-anthesis stage, was more pronounced. An increase in rainfall by 1 mm in this stage increased rice yield by 10 kg ha-1, with Gf as the largest contributor to this yield increase, followed by Spikelets and Gwt. The adverse effect of continuous mono cropping on yield was not large, 0.6%, or 14 kg ha-1, per an additional planting. This observed yield decline due to additional planting every season was brought about wholly by the decline in Gwt, and not by other yield components. The application of N-fertilizer mitigated the adverse effect of continuous cropping for Panicles and Spikelets but aggravated it for Gf and Gwt. The P-deficient soil at the experimental site made the effects of N-application very low if used without P-application. When applied with P-fertilizer, N-application significantly increased Panicles and Spikelets, but significantly decreased Gf and Gwt, resulting in the marginal effect of N on yield of 13 kg ha-1 per 1 kg N.
This study investigates the impact of agriculture on the water quality of the Cisadane River system in West Java, Indonesia by focusing on one stream flowing from an upland area through an intensive agricultural area before merging with the rest of the river system downstream. In total, 25 water samples were collected from this river system over a straight-line distance of ~70 km and an altitudinal difference of 750 m during the dry season of 2015 and the rainy season of 2016. The samples were analyzed to measure the pH, EC, and concentrations of NO3-N, NH4-N, and PO4-P. The average contamination in the water samples during the dry and rainy seasons was 0.61 and 0.45 mg NO3-N L-1, respectively, 0.56 and 0.28 mg NH4-N L-1, respectively, and 0.64 and 0.55 mg PO4-P L-1, respectively. The results revealed that water was contaminated by inorganic P even in the upper stream. Moreover, the spring water in the agriculture-intensive areas of a rural community, which is believed by the locals to be sufficiently clean for use, was found to more be contaminated by nitrogen than the water in the lower part of the river. As the flow of contaminated water can cause eutrophication in estuaries, it is important to characterize the contamination of water systems to encourage the implementation of sustainable water management strategies.