The impact of modern agriculture on natural resources has become a major global concern. Population growth and expanding demand for agricultural products constantly increase the pressure on land and water resources. A major point of concern for many intensively managed agricultural systems with high external inputs is the low resource-use efficiency, especially for nitrogen. A high input combined with a low efficiency ultimately results in environmental problems such as soil degradation, eutrophication, pollution of groundwater, and emission of ammonia and greenhouse gases. Evidently, there is a need for a transition of current agricultural systems into highly resource-use efficient systems that are profitable, but at the same time ecologically safe and socially acceptable. Here, opportunities to improve nitrogen-use efficiency in cropping and farming systems are analyzed and discussed. In the past and present, increased productivity of the major plant production systems has been derived from genetic improvement, and from greater use of external inputs such as energy, fertilizers, pesticides and irrigation water. Aiming at improving resource-use efficiencies, in high-input systems the focus should be on more yield with less fertilizer N. In low-input systems additional use of N fertilizer may be required to increase yield level and yield stability. Developing production systems that meet the goals of sustainable agriculture requires research on different scales, from single crops to diverse cropping and farming systems. It is concluded that N supply should match N demand in time and space, not only for single crops but for a crop rotation as an integrated system, in order to achieve a higher agronomic N-use efficiency. A combination of quantitative systems research, development of best practices and legislation will be needed to develop more environmentally-friendly agricultural systems. The growing complexity of managing N in sustainable agricultural systems calls for problem-oriented, interdisciplinary research

Nitrogen, sustainable agriculture and food security: A review

The impact of modern agriculture on natural resources has become a major global concern. Population growth and expanding demand for agricultural products constantly increase the pressure on land and water resources. A major point of concern for many intensively managed agricultural systems with high external inputs is the low resource-use efficiency, especially for nitrogen. A high input combined with a low efficiency ultimately results in environmental problems such as soil degradation, eutrophication, pollution of groundwater, and emission of ammonia and greenhouse gases. Evidently, there is a need for a transition of current agricultural systems into highly resource-use efficient systems that are profitable, but at the same time ecologically safe and socially acceptable. Here, opportunities to improve nitrogen-use efficiency in cropping and farming systems are analyzed and discussed. In the past and present, increased productivity of the major plant production systems has been derived from genetic improvement, and from greater use of external inputs such as energy, fertilizers, pesticides and irrigation water. Aiming at improving resource-use efficiencies, in high-input systems the focus should be on more yield with less fertilizer N. In low-input systems additional use of N fertilizer may be required to increase yield level and yield stability. Developing production systems that meet the goals of sustainable agriculture requires research on different scales, from single crops to diverse cropping and farming systems. It is concluded that N supply should match N demand in time and space, not only for single crops but for a crop rotation as an integrated system, in order to achieve a higher agronomic N-use efficiency. A combination of quantitative systems research, development of best practices and legislation will be needed to develop more environmentally-friendly agricultural systems. The growing complexity of managing N in sustainable agricultural systems calls for problem-oriented, interdisciplinary research.

/pdf/nitrogen-sustainable-agriculture-and-food-security-a-review-xhcgelnx5y.pdf

Nitrogen, sustainable agriculture and food security. A review.

Effect of regulated deficit irrigation on alfalfa performance under two irrigation systems in the inland arid area of midwestern China

Relevance of sprinkler irrigation time of the day on alfalfa forage production

Understanding the effects of seeding rate and cutting intervals on dry matter yield and nutritive value may help to optimize of alfalfa production. The objective of this study was to investigate the optimum cutting interval and seeding rate of two cultivars of alfalfa (cv. Alsancak and cv. Nimet). Field experiments were carried out for 3 years in Mediterranean ecological conditions. The treatments were comprised of three cutting programs at 20, 30 and 40 days interval and two seeding rates (15 and 30 kg ha-1). The experiment was designed a split–split plot in a randomized complete block with 3 repetitions. The main plots were cutting intervals, sub-plots were seeding rates and sub –subplots were assigned as alfalfa cultivars. The results of the research showed that all properties inspected were significantly affected from the cutting intervals, the effect of the seeding rate and the cultivars were found to be not significant (except fresh forage yield). While the extended cutting intervals increased the forage yield, it reduced the forage quality. In terms of satisfactory forage yield and quality for similar ecological conditions, 30 days cutting interval and 15 kg ha-1 seeding rate have been advisable.

/pdf/the-effects-of-cutting-intervals-and-seeding-rates-on-forage-307jjvbul4.pdf

The effects of cutting intervals and seeding rates on forage yield and quality of alfalfa

Persistence is a critical component of alfalfa (Medicago sativa L.) crop yield. Our objective was to determine the effect of seeding rate on alfalfa persistence, yield, and yield components and how they evolved over time in irrigated areas with long growing seasons. Two alfalfa cultivars were seeded at four seeding rates (10, 20, 30, and 40 kg ha -1 ), in three consecutive experiments, and evaluated over a 3-yr period to provide total data for nine location years. Seed rates of 10 kg ha -1 [8.75 kg ha -1 of pure live seed (PLS)] produced total 3-yr dry matter (DM) yields of between 50.8 and 58.9 Mg ha -1 . Seed rates only affected total 3-yr DM yields in one of the three experiments. The mean number of shoots per m -2 was 488 and this was not affected by seed rates. The effect of seed density on mean shoot weight depended on the experiment. The annual average crude protein (CP) concentration varied from 159 g kg -1 to 224 g kg -1 while the leaf to stem ratio varied from 0.87 to 1.17. The results suggest that CP and leaf to stem ratios (LSR) were either little influenced or not influenced by seed density. The DM yields and yield components indicate that 8.75 kg ha -1 of PLS could be sufficient to ensure adequate DM production. Results also suggest that in a Mediterranean climate in which sprinkler irrigation is applied, there is little justification for high seeding rates under good establishment conditions.

Yield, Yield Components, and Forage Nutritive Value of Alfalfa as Affected by Seeding Rate under Irrigated Conditions

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Yield, Yield Components, and Forage Nutritive Value of Alfalfa as Affected by Seeding Rate under Irrigated Conditions