Silvia Pampana

The Response of Durum Wheat to the Preceding Crop in a Mediterranean Environment

Crop sequence is an important management practice that may affect durum wheat (Triticum durum Desf.) production. Field research was conducted in 2007-2008 and 2008-2009 seasons in a rain-fed cold Mediterranean environment to examine the impact of the preceding crops alfalfa (Medicago sativa L.), maize (Zea mays L.), sunflower (Helianthus annuus L.), and bread wheat (Triticum aestivum L.) on yield and N uptake of four durum wheat varieties. The response of grain yield of durum wheat to the preceding crop was high in 2007-2008 and was absent in the 2008-2009 season, because of the heavy rainfall that negatively impacted establishment, vegetative growth, and grain yield of durum wheat due to waterlogging. In the first season, durum wheat grain yield was highest following alfalfa, and was 33% lower following wheat. The yield increase of durum wheat following alfalfa was mainly due to an increased number of spikes per unit area and number of kernels per spike, while the yield decrease following wheat was mainly due to a reduction of spike number per unit area. Variety growth habit and performance did not affect the response to preceding crop and varieties ranked in the order Levante > Saragolla = Svevo > Normanno.

Grain legumes differ in nitrogen accumulation and remobilisation during seed filling.

ABSTRACT In grain legumes, the N requirements of growing seeds are generally greater than biological nitrogen fixation (BNF) and soil N uptake during seed filling, so that the N previously accumulated in the vegetative tissues needs to be redistributed in order to provide N to the seeds. Chickpea, field bean, pea, and white lupin were harvested at flowering and maturity to compare the relative contribution of BNF, soil N uptake, and N remobilisation to seed N. From flowering to maturity, shoot dry weight increased in all crops by approximately 50%, root did not appreciably change, and nodule decreased by 18%. The amount of plant N increased in all crops, however in field bean (17 g m−2) it was about twice that in chickpea, pea, and lupin. The increase was entirely due to seeds, whose N content at maturity was 26 g m−2 in field bean and 16 g m−2 in chickpea, pea, and lupin. The seed N content at maturity was higher than total N accumulation during grain filling in all crops, and endogenous N previously accumulated in vegetative parts was remobilised to fulfil the N demand of filling seeds. Nitrogen remobilisation ranged from 7 g m−2 in chickpea to 9 g m−2 in field bean, and was crucial in providing N to the seeds of chickpea, pea, and lupin (half of seed N content) but it was less important in field bean (one-third). All the vegetative organs of the plants underwent N remobilisation: shoots contributed to the N supply of seeds from 58% to 85%, roots from 11% to 37%, and nodules less than 8%. Improving grain legume yield requires either reduced N remobilisation or enhanced N supply, thus, a useful strategy is to select cultivars with high post-anthesis N2 fixation or add mineral N at flowering.

Waterlogging at tillering affects spike and spikelet formation in wheat

Abstract. Waterlogging stress is one of the limiting factors influencing wheat (Triticum aestivum L.) production. Wheat tolerance to waterlogging is related to the duration of the waterlogging event, the crop development stage in which waterlogging occurs, and the sensitivity of genotype. In this paper we investigated the impact of eight waterlogging durations (from 0 to 60 days) imposed at 3-leaf and 4-leaf growth stages (∼30 and 40 days after sowing) on grain yield, grain yield components, straw and root dry weight and nitrogen concentration of grain, straw, and roots of two cultivars of wheat. The results showed that of the two cultivars, one (cv. Blasco) was tolerant to waterlogging and the other (cv. Aquilante) was sensitive, thus confirming that there are high genotypic differences in terms of tolerance to waterlogging in wheat. The sensitive cultivar showed a significant reduction in grain yield and straw and root dry weight only when waterlogging was prolonged for more than 20 days. Waterlogging depressed the grain yield of the sensitive cultivar, slowing tiller formation and consequently preventing many culms from producing spikes. It slowed down spikelet formation, consequently reducing the number of spikelets per spike, and reduced floret formation per spikelet, thus reducing the number of kernels per spike.

Response of cool-season grain legumes to waterlogging at flowering

Abstract: Soil flooding and submergence, collectively termed waterlogging, are major abiotic stresses that severely constrain crop growth and productivity in many regions. Cool-season grain legumes can be exposed to submersion both at the vegetative and reproductive stages. Limited research has been carried out on these crops with waterlogging imposed at flowering. We evaluated how waterlogging periods of 0, 5, 10, 15, and 20 d at flowering affected seed yield, biomass of shoots, roots and nodules, and N uptake of faba bean (Vicia faba L. var. minor), pea (Pisum sativum L.), and white lupin (Lupinus albus L.). Faba bean tolerated submersion better than pea and white lupin. Pea and white lupin plants did not survive 10 d of submersion, and after 5 d the seed yield, shoot and root biomass, and N uptake had more than halved. Faba bean survived 20 d of waterlogging, although seed and biomass production and total N uptake were severely reduced. Shoot dry weight and seed yield decreased linearly with the duration of waterlogging, which negatively affected seed more than the vegetative plant part weight. In all three crops waterlogging at flowering led to damage, which could not be recovered during seed filling.

Effects of nitrogen splitting and source on durum wheat

Optimum nitrogen fertilizer management for wheat production is important for maximum economic yield and minimum pollution of the environment. A lysimetric trial was conducted in Central Italy during 2008–2009 and 2009–2010 on durum wheat varieties Latinur and Svevo to evaluate effects of ammonium sulphate and Entec 46 at sowing, of ammonium sulphate and urea at topdressing and of three split applications (0–90–90, 30–75–75 and 60–60–60 kg N ha−1) of the same amount of nitrogen on grain yield and yield components, N uptake and N leaching. Grain yield was higher in Latinur than in Svevo. The highest production was achieved in 2009 with the 60–60–60 splitting, and in 2010 with 0–90–90. In both years, the highest total N uptake was recorded with the 30–75–75 splitting, regardless of N source. Nitrogen leaching increased with the increasing amount of N rate at sowing. Amount of N-NO3 lost by leaching during wheat cycle was 25 kg ha−1, almost entirely accounted for N leaching in the period November–January.

NITROGEN FIXATION OF GRAIN LEGUMES DIFFERS IN RESPONSE TO NITROGEN FERTILISATION

Legume crops are not usually fertilised with mineral N. However, there are at least two agronomic cases when it would be advantageous to distribute N fertiliser to legume crops: at sowing, before the onset of nodule functioning, and when a legume is intercropped with a cereal. We highlight the impact of various levels of fertiliser nitrogen on grain yield, nodulation capacity and biological nitrogen fixation in the four most common grain legume crops grown in central Italy. Chickpea ( Cicer arietinum L.), field bean ( Vicia faba L. var. minor), pea ( Pisum sativum L.) and white lupin ( Lupinus albus L.) were grown in soil inside growth boxes for two cropping seasons with five nitrogen fertilisation rates: 0, 40, 80, 120 and 160 kg ha −1 . In both years, experimental treatments (five crops and five levels of N) were arranged in a randomised block design. We found that unfertilised plants overall yielded grain, total biomass and nitrogen at a similar level to plants supplied with 80–120 kg ha −1 of mineral nitrogen. However, above those N rates, the production of chickpea, pea and white lupin decreased, thus indicating that the high supply of N fertiliser decreased the level of N 2 fixed to such an extent that the full N 2 -fixing potential might not be achieved. In all four grain legumes, the amount of N 2 fixed was positively related to nodule biomass, which was inversely related to the rate of the N fertiliser applied. The four grain legumes studied responded differently to N fertilisation: in white lupin and chickpea, the amount of nitrogen derived from N 2 fixation linearly decreased with increasing N supply as a result of a reduction in nodulation and N 2 fixed per unit mass of nodules. Conversely, in field bean and pea, the decrease in N 2 fixation was only due to a reduction in nodule biomass since nodule fixation activity increased with N supply. Our results suggest that the legume species and the N rate are critical factors in determining symbiotic N 2 -fixation responses to N fertilisation.

Nitrogen and phosphorus accumulation and remobilization of durum wheat as affected by soil gravel content

Soil gravel content affects many soil physical properties, as well as crop yield. Little is known regarding the influence of soil gravel content on growth and nutrient uptake of durum wheat (Triticum durum Desf.). The accumulation of nitrogen and phosphorous during the vegetative and reproductive periods and the contribution of pre-anthesis assimilates to grain N and P content have been evaluated in two durum wheat varieties grown on soils with 0, 10, 20 and 30% gravel content. The two varieties showed similar behaviour and the increase of soil gravel decreased plant biomass during the entire biological cycle. Nitrogen and P concentration of all plant parts was not affected by soil gravel content, while N and P content was greatly reduced, owing to the effect on dry matter yield. Post-anthesis accumulation and remobilization of N and P were greatly reduced: the decrease from gravel-free soil to 30% gravel content was about 41 kg N ha –1 and 4 kg P ha –1 for the former and 14 kg N ha –1 and 2 kg P ha –1 for the latter. The differences in growth rate were attributed to differences in development of the root system due to the restricted soil volume.

Biosolids differently affect seed yield, nodule growth, nodule-specific activity, and symbiotic nitrogen fixation of field bean

Abstract. The main aim of this research was to verify whether mineral nitrogen (N) continuously released by organic fertilisers during the field bean growth cycle may be sufficiently high to enhance plant growth and seed yield but sufficiently low that it does not negatively affect nodulation and symbiotic N2 fixation. Plants were grown without N fertilisation, and with mineral and organic N (biosolids) fertilisation. All plant parts were collected and dry matter, N content, %Ndfa, and N2 fixed were measured at 8th node, flowering, and maturity stages. Nodule specific activity, N derived from soil, and N remobilisation were estimated. The nitrate concentration of soil was also determined. Biosolids reduced nodule growth, nodule fixation activity, and N2 fixation during the vegetative but not the reproductive phase. During seed filling, nodule fixation activity increased and N2 fixation was roughly twice that of the Control plants. Biosolids increased seed yield by removing the imbalance between N demand and N supply for pod growth. This may be related to an increase in nodule-specific activity due to the reduction in mineral N in the soil.

Grain yield of durum wheat as affected by waterlogging at tillering

Waterlogging is one of the limiting factors influencing durum wheat (Triticum durum L.) production. In this paper we investigated the impact of seven waterlogging durations of 4, 8, 12, 16, 20, 40, and 60 days, imposed at 3-leaf and 4-leaf growth stages, on grain yield, grain yield components, straw and root dry weight and nitrogen concentration of grain, straw, and roots of two varieties of durum wheat. Grain yield of both varieties showed a significant reduction only when waterlogging was prolonged to more than 20 days, and 40-d and 60-d waterlogging reduced grain yield by 19% and 30%. Waterlogging depressed grain yield preventing many culms from producing spikes. It slowed down spikelet formation, consequently reducing the number of spikelets per spike, and reduced floret formation per spikelet, thus reducing the number of kernels per spike.