Jinpeng Li

Growth and Nutrient Use in Four Grasses Under Drought Stress as Mediated by Silicon Fertilizers

ABSTRACT Field water stress is a common problem in crop production, especially in arid and semi-arid zones and it is widely hypothesized that silicon (Si) could reduce water stress in plants. We set up a greenhouse study to evaluate some silicon sources—potassium silicate (K2SiO3), calcium silicate (CaSiO3) and silica gel for growth and nutrient uptake by four grass species under adequate and deficit irrigation. The four species studied were Rhodes grass (Chloris gayana), Timothy grass (Phleum pratense), Sudan grass (Sorghum sudanense) and Tall fescue (Festuca arundinacea). For all species, the biomass yield response to applied silicon under deficit irrigation was significantly better than under adequate irrigation. The yield response of Rhodes grass across silicon sources was 205% under deficit irrigation compared with only 59% under adequate irrigation; for Sudan grass it was 49% compared with 26% and for Timothy, it was 48% compared with a mere 1%. The higher responses under deficit irrigation suggest that the plants relied more on silicon to endure drought stress. Biomass yield of individual plants also differed according to soil water levels with Timothy grass being the most sensitive to water stress as it exhibited the highest yield response (209%) to adequate irrigation. This was followed by tall fescue (122%) and Rhodes grass (97%). Sudan grass was the least affected by deficit irrigation, possibly on account of improved root mass and its natural drought tolerance. Strong associations were noted between the uptake of silicon and those of nitrogen (N) and phosphorus (P) irrespective of soil water condition, but the uptake of potassium (K) was more strongly correlated with that of Si under deficit than adequate irrigation. Improvements in plant growth following Si application could therefore be linked to enhanced uptake of major essential nutrients.

Nitrogen uptake and remobilization in maize hybrids differing in leaf senescence

Maize (Zea mays L) is an important cereal crop with multiple purposes. Stay-green varieties have been considered a major progress in breeding for high yield. Nevertheless, few studies have been conducted to evaluate the influence of nitrogen (N) levels on N uptake, N remobilization in relation to grain yield and N concentration in stay-green versus early-senescing hybrids. Field studies were undertaken in P. R. China on an Ustochrepts soil to determine the effects of N levels and hybrid differing in leaf senescence on grain yield, N concentration, N uptake, N remobilization and residual N in vegetative tissues in 1996 and 1997. Results showed that ND108 (a stay-green hybrid) had greater yields than TK5 (an intermediate hybrid) and ZD120 (an early-senescening hybrid) under both high (225 kg N ha−1) and low N supply (0 in 1997 or 45 kg N ha−1 in 1996, respectively). ND108 took up more N than the two other hybrids. Grain N concentration of ND108 did not decrease significantly under low N compared to high N in 1997. However, in 1996 grain N concentration of ND108 decreased with reduced N supply, since post-silking N uptake was reduced by the shorter grain filling duration. N remobilization efficiency in vegetative tissue was higher in the early-senescening hybrid (ZD120) than in the stay-green hybrid (ND108). The N retained in the stover at harvest was much higher in ND108, which can lead to a deficit of soil N for the next crop when the stover is not returned to the field.

Response of Lowland and Aerobic Rice to Ammonium and Nitrate Supply During Early Growth Stages

ABSTRACT Decreasing fresh water availability has intensified the search for alternative rice cultivation systems with reduced water input, but most evidence suggests negative effects on growth of lowland (LL) rice cultivars. Yield in such production systems may be improved by selection of adapted aerobic ‘Han Dao’ (HD) rice cultivars. Lowland and HD rice were compared under sole nitrate or ammonium supply as well as under mixed supply of both nitrogen (N) forms during the seedling and tillering stage; pronounced differences were found in response to the supplied N form. Shoot dry mass (DM) of HD was significantly lower than that of LL under sole and predominant ammonium supply, whereas LL showed the opposite trend, with significantly lower shoot DM under sole-nitrate supply. Nitrogen concentration of LL rice under sole-nitrate supply was significantly lower compared with other treatments at tillering stage. Han Dao rice had a significantly higher potassium (K) concentration than LL rice under sole-nitrate supply, while the opposite result was observed under sole-ammonium supply. At seedling stage, the portion of N that was taken up from nitrate-N varied from 30% to 40% in HD and LL rice in treatments 75N/25A and 50N/50A, while at both growth stages, predominant ammonium supply resulted in a lower portion (20%) of nitrate-derived N in LL than in HD rice. The portion of nitrate-derived N increased at tillering stage (from 40% to 70%). These results further illustrate a synergistic effect of co-provision of nitrate and ammonium on total N fluxes compared with supply of sole nitrate or sole ammonium. It was concluded that the interaction between N form and tiller formation during early growth stages deserves strong attention for the identification of aerobic rice cultivars.

Cultivar Mixture Cropping Increased Water Use Efficiency in Winter Wheat under Limited Irrigation Conditions

The effects of cultivar mixture cropping on yield, biomass, and water use efficiency (WUE) in winter wheat (Triticum aestivum L.) were investigated under non-irrigation (W0, no irrigation during growth stage), one time irrigation (W1, irrigation applied at stem elongation) and two times irrigation (W2, irrigation applied at stem elongation and anthesis) conditions. Nearly 90% of cultivar mixture cropping treatments experienced an increase in grain yield as compared with the mean of the pure stands under W0, those for W1 and W2 were 80% and 85%, respectively. Over 75% of cultivar mixture cropping treatments got greater biomass than the mean of the pure stands under the three irrigation conditions. Cultivar mixture cropping cost more water than pure stands under W0 and W1, whereas the water consumption under W2 decreased by 5.9%–6.8% as compared with pure stands. Approximately 90% of cultivar mixtures showed an increase of 5.4%–34.5% in WUE as compared with the mean of the pure stands, and about 75% of cultivar mixtures had 0.8%–28.5% higher WUE than the better pure stands under W0. Similarly, there were a majority of mixture cropping treatments with higher WUE than the mean and the better one of the pure stands under W1 and W2. On the whole, proper cultivar mixture cropping could increase yield and WUE, and a higher increase in WUE occurred under limited irrigation condition.

Reduced irrigation increases the water use efficiency and productivity of winter wheat-summer maize rotation on the North China Plain

The groundwater table has fallen sharply over the last 30years on the North China Plain, resulting in a shortage of water for winter wheat irrigation. Reducing irrigation may be an important strategy to maintain agricultural sustainability in the region; however, few studies have evaluated the transition from conventional irrigation management practices to reduced irrigation management practices in the winter wheat-summer maize rotation system. Here, we compare the yield, water consumption, and water use efficiency of winter wheat-summer maize rotation under conventional irrigation and reduced irrigation on the North China Plain from 2012 to 2015. Reducing irrigation decreased the yield but increased the water use efficiency and significantly advanced the harvest date of winter wheat. As a result, the summer maize sowing date advanced significantly, and the flowering date subsequently advanced 2-8days, thus extending the summer maize grain-filling stage. Therefore, the yield and water use efficiency of summer maize were higher under reduced irrigation than conventional irrigation, which compensated for the winter wheat yield loss under reduced irrigation. In addition, under reduced irrigation from 2012 to 2015, the yield and water use efficiency advantage of the winter wheat-summer maize rotation ranged from 0.0 to 9.7% and from 4.1 to 14.7%, respectively, and water consumption and irrigated water decreased by 20-61mm and 150mm, respectively, compared to conventional irrigation. Overall, the reduced irrigation management practice involving no irrigation after sowing winter wheat, and sowing summer maize on June 7 produced the most favorable grain yield with superb water use efficiency in the winter wheat-summer maize rotation. This study indicates that reducing irrigation could be an efficient means to cope with water resource shortages while maintaining crop production sustainability on the North China Plain.

Micro-irrigation improves grain yield and resource use efficiency by co-locating the roots and N-fertilizer distribution of winter wheat in the North China Plain

Water use efficiency (WUE) and nitrogen fertilizer use efficiency (NUE) of winter wheat are urgently needed to further improve in the North China Plain (NCP). In this study, a 3-year field experiment was conducted during the 2014-2017 growing seasons to clarify the effect of traditional flood irrigation (TI), surface drip irrigation (DI), and micro-sprinkling irrigation (MSI) on grain yield, WUE, and NUE of winter wheat. Across the 3 years, grain yield of DI and MSI improved by 9.79% and 14.1%, WUE of DI and MSI increased by 12.3% and 17.7%, and NUE of DI and MSI increased by 9.77% and 14.0%, respectively compared with those of TI. Wheat subjected to the micro-irrigation treatments (DI and MSI) had higher chlorophyll content in flag leaves 10 days post-anthesis; this postponed senescence of the flag leaves, which increased dry matter accumulation post-anthesis, and increased 1000-grain weight and grain yield. The micro-irrigation treatments reduced pre-anthesis water consumption but increased post-anthesis water consumption and ensured the water supply in the top soil layer at the critical stage, thus increasing WUE. Root length density (RLD) of TI in the 0-80-cm soil layer was significantly higher than that of micro-irrigation, whereas micro-irrigation had higher RLD than TI below the 80-cm soil layer, which promoted the absorption and utilization of water and nitrogen in deep soil. The micro-irrigation treatments increased total nitrogen accumulation of the plants, reduced soil nitrate nitrogen (NO3--N) content at maturity, ensured the nitrogen supply in the top soil layer, thus increasing NUE. Overall, micro-irrigation with water and fertilizer as an integrated pattern significantly improved grain yield, WUE, and NUE of winter wheat in the NCP by co-locating the root, water, and N-fertilizer distribution and reducing NO3--N accumulation in deep soil. The best treatment was micro-sprinkling irrigation.

Optimizing single irrigation scheme to improve water use efficiency by manipulating winter wheat sink-source relationships in Northern China Plain

Improving winter wheat grain yield and water use efficiency (WUE) with minimum irrigation is very important for ensuring agricultural and ecological sustainability in the Northern China Plain (NCP). A three-year field experiment was conducted to determine how single irrigation can improve grain yield and WUE by manipulating the “sink-source” relationships. To achieve this, no-irrigation after sowing (W0) as a control, and five single irrigation treatments after sowing (75 mm of each irrigation) were established. They included irrigation at upstanding (WU), irrigation at jointing (WJ), irrigation at booting (WB), irrigation at anthesis (WA) and irrigation at medium milk (WM). Results showed that compared with no-irrigation after sowing (W0), WU, WJ, WB, WA and WM significantly improved mean grain yield by 14.1%, 19.9%, 17.9%, 11.6%, and 7.5%, respectively. WJ achieved the highest grain yield (8653.1 kg ha-1) and WUE (20.3 kg ha-1 mm-1), and WB observed the same level of grain yield and WUE as WJ. In comparison to WU, WJ and WB coordinated pre- and post-anthesis water use while reducing pre-anthesis and total evapotranspiration (ET). They also retained higher soil water content above 180 cm soil layers at anthesis, increased post-anthesis water use, and ultimately increased WUE. WJ and WB optimized population quantity and individual leaf size, delayed leaf senescence, extended grain-filling duration, improved post-anthesis biomass and biomass remobilization (source supply capacity) as well as post-anthesis biomass per unit anthesis leaf area (PostBA-leaf ratio). WJ also optimized the allocation of assimilation, increased the spike partitioning index (SPI, spike biomass/biomass at anthesis) and grain production efficiency (GPE, the ratio of grain number to biomass at anthesis), thus improved mean sink capacity by 28.1%, 5.7%, 21.9%, and 26.7% in comparison to W0, WU, WA and WM, respectively. Compared with WA and WM, WJ and WB also increased sink capacity, post-anthesis biomass and biomass remobilization. These results demonstrated that single irrigation at jointing or booting could improve grain yield and WUE via coordinating the “source-sink” relationships with the high sink capacity and source supply capacity. Therefore, we propose that under adequate soil moisture conditions before sowing, single irrigation scheme from jointing to booting with 75 mm irrigation amount is the optimal minimum irrigation practice for wheat production in this region.

Dry matter and nitrogen accumulation and remobilization in wheat as affected by genotype and irrigation

ABSTRACT To investigate the genotypic differences of dry matter (DM) and nitrogen (N) accumulation and remobilization as well as the photosynthetic characteristics of flag leaf during grain filling under water-limited conditions, nine winter wheat cultivars were planted under two irrigation treatments including W0 (no irrigation applied during spring) and W2 (1500 m3 ha−1 applied 50% at stem elongation and 50% at anthesis). Results showed that cultivar and irrigation significantly affected the accumulation and remobilization of DM and N as well as the photosynthetic characteristics of flag leaf. No irrigation in spring on average decreased the photosynthetic rate of flag leaf, accelerated leaf senescence, and consequently decreased the accumulation of DM and N, but increased the ear distribution ratio and the remobilization and contribution of DM and N in leaf and stem to grain. Maintaining high photosynthetic activity and promoting DM and N distribution in ear and the remobilization of DM and N in leaf and stem may lead to higher grain filling rate and lower yield loss under water-limited conditions in North China Plain.