Fertilizer input

F or NjO, estimates of soil emissions are perhaps slightly more straightforward, simply because so much more information on soil NjO emissions is available. For agricultural soils, estimates as a percentage of fertilizer input have been published " and, for the remaining land use classes listed in Table 5, mean annual emissions from a series of long-term flux measurements are available. The total annual soil NjO emissions for the ElK (27 kt N) are very similar to the annual soil NO emissions. Soils, however, have by far a greater impact on the... 

These results clearly indicate that fruit growers should not lower fertility inputs below the level required for satisfactory tree performance and intrinsic fruit quality, and also content of polyphenols. Thus, balanced nutrition without over or under supply of nutrients should be targeted in organic fruit production. 

Kwabiah AB, Stoskopf NC, Palm CA, Voroney RP, Rao MR, Gacheru E (2003) Phosphorus availability and maize response to organic and inorganic fertilizer inputs in a short term study in western Kenya. Agric Ecosyst Environ 95 49-59... 

Dobermann A, Santa Cruz PC, Cassman KG. 1996. Fertilizer inputs, nutrient balance, and soil nutrient-supplying power in intensive, irrigated rice systems. I. Potassium uptake and K balance. Nutrient Cycling in Agroecosystems 46 1-10. 

Because of the low P content (usually < 0.2 %) of forage plants, P supplementation is commonly practiced in most ranches throughout the Amazon basin, particularly in Brazilian Amazonia. Assuming a stocking rate of 0.8 animal units per hectare per year, the annual input of P to the system through animal consumption of mineral supplementation would be around 2.0 kg, which is close to the amount expected to be exported annually by animal products (2.5 kg). The amount thus needed to balance the cycle would be only 0.5 kg. In the absence of phosphate fertilizer inputs, this P must come from the soil pool reserves, through forage consumption. 

In summary, in high-yield, short-rotation plantation forestry in rain forest sites such as Jari, and other locations with similar ecological conditions, nutrients are likely to become limiting after the second or third rotation therefore, yields will not be maintained without extra fertilizer inputs. Repeated fertilization can upset soil nutrient balances and alter microbial populations, and it would also pose problems for the economics of producing low-value commodity timbers (see also Jordan, this volume). 

In 1982, Science reported that technology had been developed which permitted continuous production of annual crops in acid, infertile soils of the Amazon basin (Sanchez et al. 1982), The studies in Yurimaguas Peru showed that three grain crops can be produced annually with appropriate fertilizer inputs. Twenty-one crops were harvested from one field in 8 1/2 years, with an average yield of 7.8 tons of grain per hectare. Soil properties were said to improve with continuous cultivation. 

The general way for the estimation of fertilizer input is the statistical data on national and regional application of fertilizers under different crops. The national statistic yearbooks and international FAO statistic is of usefulness. 

Figure 5. Application of nitrogen in fertilizer and by atmospheric deposition ofFiOy to 13 of the watershed regions. Values are in kg N/km /year. Fertilizer inputs dominate net anthropogenic nitrogen inputs in most, but not all, regions of the North Atlantic basin (Howarth, 1996).

Figure 6a. Plot of river nitrogen export versus net human-derived nitrogen inputs to each of the temperate regions (all European and North American region, except the Western Gulf of Mexico) net inputs are equal to the sum of anthropogenic NOy deposition, fertilizer inputs, nitrogen fixation by crops, and the net import or export of nitrogen in food and feed. (Howarth, 1996).

Nitrogen deposition enters the ecosystem as a slow, steady input rather than in one or a few large doses - this is especially the case with fertilizer input - which is important with respect to nitrification and nitrate leaching (Diese and Wright 1995). 

Reddy et al. (1999). In this study, the amount of total phosphorus lost during 4 years was similar to the amount of phosphorus exported with harvest products. Loss of total phosphorus in the Tanzanian trial after 3 years of cultivation translated into an annual loss of 83 kg P/ha, whereas after 15 years an additional phosphorus loss of only 44 kg P/ha was observed (Solomon and Lehmann, 2000). Clearly, other pathways of phosphorus loss, such as erosion of phosphorus-enriched topsoil after woodland clearing, must have been relevant. Likewise, annual phosphorus losses of 17—19 kg P/ha in a study from Ethiopia (Solomon et al., 2002) appear to be at the high end for phosphorus exports from unfertilized maize. In addition, significant reductions in total phosphorus under plantations of tea and Cupressus, despite low mineral fertilizer inputs, suggest that phosphorus loss through erosion and/or leaching occurred. 

The projections of inputs growth rate are made by the scenairio method the most probable dynamics of the growth are selected. By comparing the ratio of the fertilizer input contribution to the crops (in particular cereals), the yield growth of the fertilizer input or its efficiency at a given intensity could be analyzed. 

Breeding for yield is a complex task, because the final measure is the dry seed, the raw cacao after complex postharvest treatment. Before harvesting ripe pods, there are many steps which depend on the interaction of the plant with environmental factors. This field is still under intensive evaluation, especially under management aspects for the decision if a cacao plantation shall be run under shade trees or in direct stm. Directly combined with these decisions is the shorter lifetime of plantations in direct sun, the high investment costs for high fertilizer input, and the potential need for irrigation [5, 17]. 

Microbial activity is important for the conversion of ammonium, resulting from mineralization of organic-N or from fertilizer input, into nitrite and then nitrate. These ions are reactive chemical species which can combine with soil organic matter to produce "fixed" N which may be unavailable to plants. 

Adaptive salt tolerance by plants or salt stress itself (Table 1) has been noted to give rise to changes in the proportions of membrane lipid classes as well as to their acyl composition. Some stresses are due to ionic effects which could be caused by almost any salt while others are due to specific toxicology as a result of particular ions [see 3]. Often agricultural practices will lead to sufficient fertilizers inputs to cause changes in plant lipid metabolism or to interact with other environmental factors (see below for the Greenhouse Effect). 

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