Shah Jahan Leghari

Groundwater is an important natural resource in the North China Plain (NCP) with high economic benefits and social significance. It fulfills 60% of drinking and 70% of irrigation water requirements. In this review, the information is retrieved from high-quality articles published in MEDLINE and other sources. We saw that groundwater is declining faster (>1 m yr⁻¹) and polluting with NO₃⁻ (>30 mg L⁻¹) due to excessive water pumping and application of a nitrogen (N) fertilizer, respectively. The water pumping (>600 mm ha⁻¹ yr⁻¹) for agricultural purposes in the region is higher than the recharge amount (−1). The low recharge is the result of low rainfall (800 mm yr⁻¹) under the impact of dominant vegetative characteristics of winter wheat–summer maize (W_W-S_M) rotations, covering >80% of the land. Furthermore, N application exceeds the crop assimilation capacity (>250 kg ha⁻¹ yr⁻¹) and leach deep down (>50 kg ha⁻¹) as well as loss in the atmosphere. Presently, Beijing, Tianjin, and Hebei are ecologically the most affected areas. We suggest that excessive water and N fertilizer use for intensive cropping systems should be controlled by paying high attention to groundwater-friendly farming practices. In addition, artificial groundwater recharge options and their safe utilization would be explored across the region to replenish aquifers. This literature review contributes valuable insights to the knowledge bank and offers a foundation for further research and policy development.

China is one of the regions with the most frequent drought disasters and serious social and economic losses. Agricultural drought is the most serious natural disaster. Due to climate change, the regional agricultural drought risk assessment has always been the focus of the academic circle. This study takes Zunyi City as an example, which is the most typical city of karst landform development. The monthly precipitation data set of ground meteorological observation stations in Zunyi City from 1956 to 2020 was selected, and the drought characteristic variables were extracted by the coupled use of the precipitation anomaly percentage (Pa) index and the theory of runs. A copula function was applied to establish the joint distribution model of characteristic variables, obtaining the drought frequency and drought return periods. Combined with the Jensen model, the agricultural drought loss rate under different drought return periods in the target year (2020) was calculated and evaluated. The results showed that the Gumbel-Hougaard copula function was suitable for the joint distribution of drought joint variables in Zunyi City. From 1956 to 2020, fewer droughts occurred in Zhengan and Wuchuan, and the most droughts took place in Fenggang, Meitan, and Yuqing. The average drought duration in each county was about 1.5 months, and the average drought severity was about 0.35 in spatial distribution. Crop loss rate caused by drought increased and the affected area expanded with the increase of drought return periods (5, 10, 20, 50, and 100 years) in temporal distribution. Meanwhile, the drought disaster was most drastic in the eastern region, followed by the south, north, west, and central area. The results were highly consistent with the historical drought in Zunyi City, which verified the validity of the model. This study could provide scientific knowledge for drought resistance and reasonable mitigation programing for the security of the regional agricultural production and the sustainability of social and economic development.

Soil compaction easily causes root hypoxia stress, resulting in poor root growth and the absorption of soil water and nutrients. We hypothesized that aerated irrigation (AI) could enhance nutrient uptake and utilization, thus unlocking the high yield potential by increasing soil aeration and root morphology indicators compared with that in the non-aeration treatment. A greenhouse experiment was conducted to investigate the effect of soil aeration and root morphology on the yield of greenhouse cucumbers. The dissolved oxygen (DO) in irrigation water at 10 mg L⁻¹ (A₁), 20 mg L⁻¹ (A₂), and non-aeration treatment (A₀) were applied via a subsurface drip irrigation system. The soil respiration rates, DO in soil water, root morphology, and crop yield were measured. The results showed that AI could significantly improve the soil respiration rate, DO in soil water, and root morphology compared with non-aeration treatment. The A₂ significantly increased soil respiration rate by 11.63% and 11.93%, respectively, compared with the A₁ and A₀ treatments. Under A₁ and A₂, the DO in soil water increased by 20.01% and 18.02%, respectively, compared with the A₀. Moreover, during the flowering and fruit set, the mature, and the late stages, the root surface area, root volume, root tip number, root forks, and root dry weight in the A₂ treatment significantly increased than that in the A₀ treatment. The soil respiration rate, DO in soil water, root length, and root forks were the main indexes correlated to the yield, respectively. The DO in soil water and root forks number significantly influenced the yield. The cucumber yield and economic benefits in A₂ peaked at 53.04 t ha⁻¹ and 3.95 × 10⁴ USD ha⁻¹, increased by 7.86% and 7.30% compared with that in the A₀ treatment, respectively (p < 0.05). The results could provide technical support and scientific knowledge for regulating greenhouse cucumbers under AI.

The problems of high nitrogen (N) fertilizer application rate and low N utilization efficiency are common worldwide in vegetable plantations. Application of brown coal (BC, also known as lignite) can increase crop yield and fertilizer N recovery efficiency (NRE). However, the effect of BC application on the utilization and distribution of exogenous N in the soil–plant system under different fertilization strategies is unclear. The pot experiment was set up in three factors of randomized design, including ¹⁵N-labeled urea fertilizer, BC, and organic manure, and pakchoi was used as the test crop. There were five rates of ¹⁵N-labeled urea, including 0, 100, 200, 300, and 400 kg N ha⁻¹, two rates of BC with 5 and 0 t ha⁻¹, and the organic manure with 0 t ha⁻¹ which constitutes ten treatments. The other four treatments were the combination of one ¹⁵N-labeled urea rate of 100 kg N ha⁻¹, two rates of BC with 5 and 0 t ha⁻¹, and two rates of organic manure with 100 and 0 kg N ha⁻¹. In conclusion, the interaction of all N fertilizer rates combined with BC improved soil ¹⁵N retention efficiency by 10.14% compared without BC amendment. Between 200 and 300 kg N ha⁻¹, the average potential loss rate of ¹⁵N decreased by 10.41%. The application of BC could reduce N loss by enhancing plant N uptake and increasing soil retention. The combined use of 200 kg N ha⁻¹ fertilizer and 5 t ha⁻¹ of BC would maintain a high fertilizer NRE and ensure pakchoi yield.

Studying the response of winter wheat to post-drought rehydration is conducive to understanding the efficient utilization of water-saving technology, such as regulating deficit irrigation and increasing water use efficiency. The controlled condition experiment in the rain shelter was conducted in 2020. The two water stress treatments, including post-drought rehydration at the jointing and heading stages, were combined with high nitrogen (N) (250 kg/hm²), low N (125 kg/hm²), and no N (0 kg/hm², control). The effects of post-drought rehydration on the relative chlorophyll content (SPAD), major fluorescence parameters, and photosynthetic indexes of winter wheat were determined. The results showed that post-drought rehydration increased the SPAD value, the efficiency of light energy conversion, maximum potential photo-electron transport, and the photosynthetic indices and decreased the photochemical quenching coefficient. Among them, the compensatory effect of rehydration at the heading stage on SPAD, fluorescence parameters, and photosynthetic indexes was more significant (p < 0.05), and the winter wheat needed a recovery process after rehydration. Increased application of N fertilizer can alleviate the effects of water stress on the fluorescence parameters and photosynthetic properties of flag leaf and promote the degree of the response of fluorescence parameters and photosynthetic properties to rehydration. The specific effects were as follows: high N > low N > no N application. As a result, winter wheat had a certain compensatory effect of rehydration after timely drought stress; the compensatory effect of rehydration could be enhanced under the condition of increasing N application.

The North China Plain (NCP) is experiencing serious groundwater level decline and groundwater nitrate contamination due to excessive water pumping and application of nitrogen (N) fertilizer. In this study, grain yield, water and N use efficiencies under different cropping systems including two harvests in 1 year (winter wheat–summer maize) based on farmer (2H1Y)^FP and optimized practices (2H1Y)^OPT, three harvests in 2 years (winter wheat–summer maize–spring maize, 3H2Y), and one harvest in 1 year (spring maize, 1H1Y) were evaluated using the water-heat-carbon-nitrogen simulator (WHCNS) model. The 2H1Y^FP system was maintained with 100% irrigation and fertilizer, while crop water requirement and N demand for other cropping systems were optimized and managed by soil testing. In addition, a scenario analysis was also performed under the interaction of linearly increasing and decreasing N rates, and irrigation levels. Results showed that the model performed well with simulated soil water content, soil N concentration, leaf area index, dry matter, and grain yield. Statistically acceptable ranges of root mean square error, Nash–Sutcliffe model efficiency, index of agreement values close to 1, and strong correlation coefficients existed between simulated and observed values. We concluded that replacing the prevalent 2H1Y^FP with 1H1Y would be ecofriendly at the cost of some grain yield decline. This cropping system had the highest average water use (2.1 kg m⁻³) and N use efficiencies (4.8 kg kg^–1) on reduced water (56.64%) and N (81.36%) inputs than 2H1Y^FP. Whereas 3H2Y showed insignificant results in terms of grain yield, and 2H1Y^FP was unsustainable. The 2H1Y^FP system consumed a total of 745 mm irrigation and 1100 kg N ha^–1 in two years. When farming practices were optimized for two harvests in 1 year system (2H1Y)^OPT, then grain yield improved and water (18.12%) plus N (61.82%) consumptions were minimized. There was an ample amount of N saved, but water conservation was still unsatisfactory. However, considering the results of scenario analyses, it is recommended that winter wheat would be cultivated at <200 mm irrigation by reducing one irrigation event.

The limiting of water resource and traditional farming practices are threatening the sustainability of important minor crops in Pakistan, including berseem, which is a key source of fodder for dairy farms. Each year, 2% reduction of cultivated area, low yield and grower’s non-preference (to rotate or replace wheat-cotton pattern) factors are adversely affecting the livestock sector. Consequently, animal rearing business is suffering badly due to lack of fresh forage in the country. Therefore, a three-replicated randomized complete block design (RCBD) field experiment was conducted during rabi season to evaluate berseem crop in term of yield and profit under existing farming practice (85:115:00 NPK kg ha⁻¹ + 12 irrigations with 15 days intervals) and optimized treatments (70:100:30 NPK kg ha⁻¹, 55:85:15 NPK kg ha⁻¹ + 12, 08, 04 irrigations + 15, 18, 21 days intervals). The net plot size was 12 m² with a pH range of 8.1 silty clay loam soil type. In addition, the climate was monitored as well, there was no rainfall observed during the entire crop period. The analysis of statistical data showed a significant (p < 0.05) vegetative, reproductive and economic performance of berseem in optimized farming practices compared to traditional practice. Thus, maximum plant height, leaves plant⁻¹, branches plant⁻¹, plant weight, fodder and seed yield, net profit, and profit on $⁻¹ (81.8 cm, 100.8, 36.0, 19.3 (g), 72.0 t, 829.30 kg ha⁻¹, $1910.8 ha⁻¹, $2.03 respectably) were measured from treatment 70:100:30 NPK kg ha⁻¹ + 12 irrigations at 15 days intervals, which is recommended to the farmers of synonymic agro-environmental conditions. Furthermore, the treatment 70:100:30 NPK kg ha⁻¹ + 8 irrigations was also better with the aspect of satisfactory outcome and 33% less use of water.