Grain yield, and dry matter and nitrogen accumulation and remobilization in durum wheat as affected by variety and seeding rate

The influence of crop density on the remobilization of dry matter and nitrogen from vegetative plant parts to the developing grain, was investigated in the durum wheat (Triticum durum Desf.) varieties Creso, Simeto and Svevo cultivated in the field at three seeding rates, 200, 250 and 400 seeds m⁻². Variety × seeding rate interaction was unsignificant for all recorded characters. Grain yield declined in the order Svevo > Simeto > Creso. Yield differences mainly depended on the different number of kernels per unit land and, secondly, on mean kernel weight. Spike components differed among varieties: Svevo and Simeto showed more kernels per spikelet and Creso more spikelets per spike. Grain yield was highest with 400 seeds m⁻² primarily due to the higher number of spikes per unit area, and secondly, to the higher mean kernel weight. Post-heading dry matter accumulation was highest in Svevo and lowest in Creso, but varieties showed a reverse order for dry matter remobilization and contribution of dry matter remobilization to grain yield. The increase of seeding rate increased both the post-heading dry matter accumulation and the dry matter remobilization from vegetative plant parts to grain. Nitrogen uptake of the whole crop and N content of grain was higher in Simeto and Svevo than in Creso. The N concentration of grain did not vary among varieties, but Svevo showed a markedly lower N concentration and N content of culms at maturity, which may be consequence of the high N remobilization efficiency performed by this variety. The N uptake by the crop was highest with 400 seeds m⁻², but the N concentration of culms, leaves and even grain was slightly lower than with the lower seed rates. The post-heading N accumulation was by far higher in Simeto and Svevo than in Creso, whereas remobilization was highest in Svevo and lowest in Simeto. The percentage contribution of N remobilization to grain N was by far higher in Creso than in the other two varieties. Post-heading N accumulation and N remobilization were highest with the highest plant density, but the contribution of N remobilization to N grain content did not differ between seeding rates.     

Optimizing forage yield of durum wheat/field bean intercropping through N fertilization and row ratio

Intercropping (IC) cereals and legumes could be an option for obtaining forage suitable for ensiling and enabling reduced N fertilization. Two experiments were performed in central Italy with durum wheat (Triticum durum Desf.) and field bean (Vicia faba L. var. minor) grown for forage production in IC and as sole crops (SC) with different N rates (20 and 50 kg ha^?1) and row ratios (1:1 and 2:1 cereal/legume). The aims were to assess (i) whether IC is a feasible option to reduce N fertilization; (ii) the best combination of practices to obtain forage suitable for ensiling; and (iii) competition/facilitation effects exerted by field bean on durum wheat. Results showed IC allowed fertilizer‐N reduction and led to improved forage yield with better quality, compared with SC. Land equivalent ratio indicated a high efficiency of the IC, by up to 26% with respect to SC. Field bean was the dominant species of IC, but N fertilization reduced its competitive ability and enhanced that of wheat. In the intercrop fertilized with 50 kg N ha^?1, the proportion of the wheat in the herbage (0·34–0·41 of the total dry matter) was sufficient for ensiling of the forage mass. Field bean exerted both competition and facilitation effects on the cereal. N uptake of durum wheat was greater under IC with beans than as wheat SC.     

Above‐ and below‐ground competition between barley,wheat, lupin and vetch in a cereal and legume intercropping system

The effects of intercropping on dry weight (DW) of herbage and nitrogen (N) nutrition of plants of two winter cereals, barley and wheat, and two legumes, white lupin and common vetch, were investigated, and above‐ and below‐ground competition were separated in a fully factorial additive design. Intercropping increased DW compared with the sole species and the increase was higher for the cereals and lupin than for cereals and vetch intercropping systems. Above‐ground competition for light reduced DW of cereals and lupin while it did not influence the DW of vetch. Processes involved in below‐ground competition increased shoot growth of cereals and reduced shoot growth of legumes. N nutrition of cereals was enhanced by below‐ground competition with legumes and N nutrition of vetch was enhanced by above‐ground competition with cereals. Cereals had a higher competitive ability than legumes as a result of their below‐ground competitive ability. The interaction between above‐ and below‐competition is not predictable: negative, positive and no interaction (additivity) between different types of competition were found. In low‐input intercropping systems, when a N‐fixing species is present, the mixture of the roots of components is important for the utilization of the soil resources and, when a climbing species is also present, the mixture of shoots can result in an increased utilization of light.     

Grain legumes differ in nitrogen accumulation and remobilisation during seed filling

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.     

Changes in biological properties and antioxidant capacity of an agricultural soil amended with sewage sludge

The effects of applying sewage sludge (SS) to agricultural soil (at low rate of 22.5, LRS, and at high rate of 45 t ha^?1 dry basis, HRS) were monitored over a 120-d experimental period. Total organic carbon (TOC), water-soluble organic carbon (WSOC), alkali-soluble phenols, basal respiration, specific enzyme activity, dehydrogenase activity (DH-ase), metabolic potential (MP) and FDA-hydrolytic activity (FDA) were strongly increased by both rates of SS applications. In the SS amended soil, about 70% of the organic C added with the material remained at the end of the experiment. Basal respiration increased with increasing SS doses. The specific enzyme activity and the MP indicate an increase in the enzyme activity in soil.

The addition of SS led to higher values than the control of all the tested parameters up to the end of the experimental period. The antioxidant capacity (trolox equivalent antioxidant capacity, TEAC) was influenced by SS addition only when applied at HRS. After 120 days only HRS value of TEAC (5.13 mM g^?1) was higher than control (4.09 mM g^?1). The pattern of TEAC did not enable any link to be established between antioxidant capacity and both alkali-soluble phenols and basal respiration in soil.     

Influence of copper on root growth and morphology of Pinus pinea L. and Pinus pinaster Ait. seedlings

We assessed the effects of Cu on root growth and morphology of stone pine (Pinus pinea L.) and maritime pine (Pinus pinaster Ait.) seedlings grown in culture solutions supplied with 0.012 (control), 0.1, 1 or 5 micro M CuSO(4). The presence of 5 micro M Cu in the nutrient solution completely inhibited root growth of both species within 3 days. In both species, taproot elongation was reduced in the presence of 1 micro M Cu, although partial growth recovery occurred after 7 days of treatment. The presence of 0.1 micro M Cu in the culture solution slightly enhanced root elongation in P. pinaster, but did not significantly influence root elongation in P. pinea. In both species, root weight per unit length increased in response to Cu exposure, and in P. pinaster, root diameter was significantly increased. The Cu treatments also affected lateral root number and length. In the presence of 1 micro M Cu, both species formed only short lateral primordia. The 1 micro M Cu treatment increased the lateral root index (number of roots per cm of root length) of P. pinaster, but decreased that of P. pinea, compared with control values. Neither the 0.1 nor 1 micro M Cu treatment had a significant effect on the mitotic index of either species. We conclude that cell elongation is more sensitive to Cu than cell division. Cell membrane damage, as indicated by Trypan blue staining, occurred after 10 days of exposure to 1 micro M Cu.     

A growth scale for the phasic development of common buckwheat

Growth scales give a standardized definition of crop development and increase the understanding among researchers and growers. In this research we defined a growth scale for the phasic development of common buckwheat that was mainly based on a sequence of easily recognizable changes occurring on the first and the terminal clusters of inflorescences formed on the main stem. Observations were carried out on plants grown in two years throughout spring. In an attempt to uniform the duration of phasic development across sowing dates, the length of phases and sub-phases was calculated in days and in thermal time using nine combinations of cardinal temperatures. A sequence of stages and various patterns of coordinated development were maintained throughout all sowings and years. Specifically, (1) the first inflorescence became visible after three true leaves had fully expanded on the main stem; (2) flowering reached the terminal inflorescence cluster before full-sized green fruits became visible in the first inflorescence, and (3) fruit ripening in the whole plant ended within two weeks of the end of ripening in the oldest inflorescence. Plant size was increased with the delay of sowing, and the length of the growth cycle was by approximately 400°Cd longer when plants experienced a day length longer than 15?h. This changed the correspondence between flowering and ripening stages, so that full flowering was associated with the development of green fruits in the first inflorescence when the cycle was short, but with their development in the terminal cluster when it was long. Trends in grain yield did not correspond to those in plant size and phase length. We are confident that this growth scale will be a valuable tool for following the progress of buckwheat development and to predict growth patterns and harvest time in response to temperature and photoperiod.