Weather parameters during the study period
During the cropping seasons (July–April), the highest rainfall of 1368 mm was received in 2013-14, followed by 1230.2 mm in 2016-17, while only 600–900 mm was received in 2014-15, 2015-16, 2017-18, 2018-19 and 2019-20. Most of the rainfall was received during the three months (July–September), accounting for nearly 80% of the total rainfall. During winters, the common occurrence of the western disturbances in the north-western India resulted in a very less rainfall. The amount of rainfall received during the October–April was least in 2015-16 (22 mm) and 2017-18 (39.4), while 100–350 mm was received in rest of the years (Supplementary Table 1).
Seven years’ trends and pooled grain and stover yields of maize
Crop establishment practices (CEP) had a significant (p<0.05) effect on the grain and stover yields of maize over the study years. In this study, initial years showed a reduction in the grain yield, but from third year onward, the yield increased significantly in the CA plots over the CT. Grain yield under the ZTFB and PNB significantly outperformed the CT across the years, except during 2014 and 2015, whereas, the CT had similar yield to the ZTFB in 2013. (Fig. 2a). Across the years, nutrient expert (NE®) and the recommended fertilization (RDF) resulted in similar yield, but being significantly superior to the FFP. However, the NE® had significantly higher yield over the RDF during 2019 (Fig. 2b). On the basis of the pooled data, the PNB and ZTFB had similar grain yield, which was 13.3% and 12.7% higher over the CT, respectively. Similarly, the NE® and RDF recorded significantly higher pooled grain yield, which was 25.7% and 22.3% higher than the FFP, respectively (Table 2).
In all the years, the ZTFB and the PNB had similar stover yields, but being significantly higher than the CT (Fig. 2c), and had 12.4% and 12.2% higher pooled yield over the CT, respectively. Furthermore, the stover yield under the NE® and RDF significantly outdo the FFP across the years, whereas the NE® had significantly greater stover yield than the RDF, except during 2017 and 2018 (Fig. 2d). The seven years' average showed that the NE® and RDF produced 25.8% and 17.6% greater stover yields than the FFP, respectively (Table 2).
Seven years’ trends and pooled seed and stover yields of chickpea
In all the years, the PNB produced maximum seed yield, except in 2016-17 (Fig. 3a), followed by the ZTFB. The NE® was the best, except during 2017-18 and 2018-19, with no difference among the FFP, RDF and NE® in 2014-15, 2015-16, 2017-18 and 2018-19 (Fig. 3b). The PNB had 10.8% and 21.5% greater pooled seed yield than the ZTFB and CT, respectively (Table 2).
The PNB and ZTFB had similar chickpea stover yield, being significantly (p<0.05) greater than the CT, but in 2014-15, 2015-16 and 2019-20, the ZTFB was at par to the CT (Fig. 3c). In contrast, the NE® recorded significantly greater stover yield than the RDF and FFP, but was at par with the RDF in 2019-20 (Fig 3d). The PNB had registered maximum stover yield, which was significantly higher over the ZTFB and CT. However, the NE® plots had significantly 11.9% and 19.3% greater stover yield over the RDF and FFP, respectively (Table 2).
System productivity as maize grain equivalent yield (MGEY)
The PNB had significantly (p<0.05) greater MGEY over the ZTFB (2013-14, 2018-19) and CT, but in 2014-15 and 2015-16; no significant difference among CEP practices was observed. Thereafter, in 2016-17, the ZTFB had significantly higher MGEY (10.7–21.4%) compared to the PNB and CT; while in 2017-18 and 2019-20, the ZTFB and PNB had similar yields (Fig. 4a). In nutrient management, the NE® and RDF were comparable for the MGEY across the years, but significantly greater than the FFP. However, in 2019-20, the RDF and FFP had similar MGEY. Averaged across the seven years, the ZTFB and PNB produced 13.9–17.6% greater MGEY than the CT, however the NE® and RDF gave 10.7–20% (seven years' mean) greater MGEY than the FFP (Fig. 4b).
Interaction effect (CEP × nutrient) on the MGEY
CEP and nutrient management had a significant (p<0.05) interaction effect on the MGEY across the years. In 2013-14, the PNB–NE® had maximum MGEY, and at par to the PNB–RDF and CT–RDF. Similarly, in 2014–15, the PNB–NE® produced the highest MGEY, but did not differ to the PNB–RDF, ZTFB–NE®, ZT–RDF and CT–NE®. In 2015-16, the PNB–NE® had similar yield to all the treatment combinations, except CEP practices with FFP. In contrast, the ZTFB–NE® had the greatest MGEY during 2016-17, 2017-18 and 2019-20. However, it was at par to the RDF and NE®, irrespective of the CEP practices during 2016-17, 2017-18 and 2019-20. Whereas in 2018-19, the PNB–NE® exhibited the highest MGEY, and significantly greater than the ZTFB–FFP and CT (Table 3). The results of the current study also suggested that the NE® and RDF either with the PNB or ZTFB tended to have relatively more MGEY than the other conventional based CEP practices.
The seven years' mean data indicated that the CT (US$ 639.9 ha-1) was the most expensive CEP, which was 15.3% and 16.9% costlier than the PNB (US$ 541.7 ha-1) and ZTFB (US$ 531.6 ha-1), respectively. Likewise, the RDF (US$ 582.7 ha-1) accounted for the highest cultivation cost, closely followed by the NE® (US$ 576.7 ha-1), being 5% and 4.1% higher over the FFP (US$ 553.3 ha-1), respectively. In all the years, the PNB had highest net returns, whereas, in 2016-17, the ZTFB accounted for the greater returns. However, the ZTFB and PNB did not differ for the system net returns, except during 2013-14, 2016-17 and 2018-19.
The PNB (US$ 1671.1 ha-1) and ZTFB (US$ 1565.9 ha-1) had generated 28.8% and 24% higher net returns than the CT (US$ 1189.8 ha-1), respectively. Similarly, the NE® (US$ 1635.9 ha-1) and RDF (US$ 1528.4 ha-1) had 22.8% and 17.4% greater net returns than the FFP (US$ 1262.9 ha-1) plots (Table 4), respectively.
Sustainable yield index (SYI)
Among the CEP in maize, the PNB had the greater SYI, but being at par to the ZTFB, which was 15% and 13.2% greater than the CT. Further, SYI was the highest under the NE®, similar to RDF, being 29.1% and 25.6% greater than the FFP. In case of chickpea, the SYI was highest under the PNB, which was 12.4% and 23.6% higher than the ZTFB and CT, respectively. The SYI in the NE® and RDF were at par, being 8.9–12.8% greater than the FFP (Table 2).
System water productivity (SWP)
During the first three years' of the study, the plots under the PNB (10.1–11.5 kg ha-1 mm-1) led to the highest SWP, which was significantly higher over the ZTFB (8.7 kg ha-1 mm-1) and CT (7.2–7.7 kg ha-1 mm-1), respectively. Whereas, fourth year onward, the PNB (8.4–16.1 kg ha-1 mm-1) had similar SWP to the ZTFB (9.7–15.7 kg ha-1 mm-1), but significantly higher than the CT (5.7–11.1 kg ha-1 mm-1) (Fig. 5a). Among nutrient management treatments, the NE® and RDF had similar SWP, except during 2013-14, 2016-17 and 2019-20 however, it was 20% and 14% (seven years' mean) greater than the FFP (Fig. 5b).
Soil properties – bulk density (ρb), organic carbon (OC) and microbial biomass carbon (MBC)
After harvest of the seventh season maize, soil samples were collected from the 0.0-0.50 m soil depth (Fig. 6a). Among the CEP, the PNB and ZTFB had significantly lower ρb than the CT up to the 0.20 m soil depth. The decrement was to the tune of 2.3–4.1% over the CT, though there was no difference in the ZTFB and PNB. In contrast, beyond the 0.20 m soil depth, ρb did not differ significantly among the CEP practices (Fig. 6a). Across the soil sections, nutrient management practices were at par for ρb (Fig. 6b). The CEP had a significant (p<0.05) impact on the soil OC up to the 0.20 m soil depth, the ZTFB and PNB were at par, but greater than the CT in the 0.0-0.20 m depth. However, there was no difference in the 0.20-0.50 m soil section (Fig. 6c). The NE® and RDF had the similar values for the OC, but significantly greater than the FFP in the 0.0-0.10 m depth, however, the SOC did not differ among the nutrient management beyond the 0.10 m soil depth (Fig. 6d).
At the silking stage of the seventh season maize, the ZTFB and PNB had similar values for the MBC, but significantly greater by 8.3-20.3% than the CT in the 0.0-0.30 m soil depth (Fig. 6e). Likewise, the NE® and RDF had similar MBC, but significantly greater than the FFP in the 0.0-0.10 m depth. However, beyond the 0.10 m soil depth, these practices did not show a significant influence on the MBC (Fig. 6f).
For the OC stock (Mg ha-1), the ZTFB and PNB had 15.5–16% higher OC stock in the upper 0.10 m soil layer, but in the 0.10-0.50 m soil depth, CEP practices did not have a significant impact on the OC stock, though relatively greater values across the depths were recorded in the ZTFB / PNB than the CT plots. Nevertheless, the total OC stock up to the 0.50 m soil depth was 9.5–12.3% greater under the CA-based CEP than the CT (Fig. 7a). The NE® had the highest OC stock across the soil layers (0.0-0.50 m), which was similar to the RDF, but 6.2% greater than the FFP (Fig. 7b). Also, the MGEY had strong relationship with the OC stock under the CA-based CEP (r2 = 0.87; p < 0.05) and the nutrient management (r2 = 0.94; p < 0.05).